CROJFE - Volume 31, Issue 1

31

Issue 1

2010

1

Original scientific paper – Izvorni znanstveni rad

Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding Karl Stampfer, Thomas Leitner, Rien Visser Abstract – Nacrtak Chokers are wire rope slings used to secure the felled trees to the rigging during cable yarder extracting. Standard chokers are set manually by the choker-setters along the corridor, and then unhooked manually by the yarder operator at the landing. Radio-controlled chokers are also set manually but have the advantage that they can be released remotely at the landing.

In addition to possible safety improvement at the landing, the advantage is that it reduces the unhook phase of the operation and thereby potentially improve productivity. However, the additional weight of the radio controlled chokers may also increase the work load of the choker-setters on the slope. A standard manual choker bell weighs 0.34 kg, whereas the radio-controlled choker bell weighs 1.6 kg. To assess the possible efficiency and ergonomic benefits of radio-controlled chokers a study was carried out on a Wanderfalke yarder. The study site was in the eastern Austrian Alps, working in Norway Spruce with a piece size ranging from 0.4 to 0.86 m3, on slopes between 50 and 60%, and in corridors of 90 to 200 m long. It included both a time and motion study in a full factorial layout as well as measuring the choker-setter workload through continuous monitoring of the heart-rate. Results showed that there was a 9% productivity gain using the radio-controlled chokers at the average piece size. However the workload of the choker-setter also increased; the percent heart rate reserve, a measurement of worker strain, increased from 40 to 44%. So although this study showed that productivity improvements are possible with radio-controlled chokers, it was at the expense of increased worked load of the choker-setter.

Keywords: radio controlled choker, cable yarding, choker-setter, ergonomic benefits

1. Introduction – Uvod Efficient harvesting in steep terrain is normally linked to cable-based harvesting systems. Technical developments and system optimization during the last decades have targeted more efficient, socially acceptable and ecologically sustainable ways to use cable yarding systems. Radio-controlled applications allow for automation of processes and enables both the yarder operator as well as the choker-setter to control the yarder (Heinimann et al. 2006).

Chokers are wire rope slings used to secure the felled trees to the rigging during cable yarder extracting. Unhooking chokers at the landing is time consuming, accounting for 10 to 20% of the productive cycle time, depending on the system (Baker et al.

2001). For operations where the yarder operator leaves his cab to unhook, the time taken to get in and out of the cab can be saved. For yarder systems where the logs are landed either next to or in front of Croat. j. for. eng. 31(2010)1

the yarder the job of the »poleman« (person who unhooks at the landing) can be saved, which also reduces the yarders operational delay time (Huyler and LeDoux 1997; Biller and Fisher 1984). Therefore automation of choker releasing is a significant opportunity for further improvement of both productivity as well as safety.

During the 1970’s the first trials of mechanical self-releasing chokers were done in Austria and Norway (Samset 1985). Use was limited due to their unreliability. It was not until the first radio-controlled chokers were developed that the potential for efficiency improvements was recognized. In addition to continued reliability problems caused by the hard working environment of cable yarding, the other main factor was a choker weight of more than 4 kg (Hemphill 1985; MacDonald 1990). Technical developments and new materials over the last two decades have allowed the operating mechanism to

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Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1–9)

become more robust and the weight of a choker to be significantly reduced – as low as 1.6 kg for smaller diameter chokers.

The classic goal of modern ergonomics is to optimize both the systems efficiency and the working conditions. The heavier weight of the radio-controlled chokers could lead to an increase of the chokersetters physical strain. It is therefore important that an increase in productivity is not at the expense of an increase of physical strain on the choker-setter.

Acquisition and maintenance costs of radio-controlled chokers are high. A manual choker typically cost 11 , but a set of four radio-controlled chokers costs 9000 (product information Giritzer). If a productivity increase is found then the question of payback time of the investment should also be considered. Currently, there is no literature available on productivity, physical strain of choker setter, work safety, and cost effectiveness. This study examines efficiency and ergonomic impacts of radio-controlled chokers and evaluates their cost-effectiveness.

with and without the use of radio-controlled chokers are alternated within one operation area.

2. Methodology – Metode istra`ivanja

The trailer mounted »Wanderfalke« yarder (company Mayr-Melnhof) extracted the whole trees to the forest road. The Sherpa U 1.5 carriage, with a maximum payload of 1.5 t, was used. Further processing of trees was done using a harvester head Kesla 20RH that is mounted on wheeled excavator base. A radio-controlled system is used so that both the operator of the processor as well as the choker-setter can control the tower yarder: there is no separate yarder operator. The processor operator also unhooks when using manual chokers.

In addition to the standard manual chokers, »Ludwig« radio-controlled chokers (Company Giritzer, Fig. 1) were used. The weight of each choker is 1.6 kg, and can be used on with a maximum choker cable diameter of 13 mm. When in use they are re-

2.1 Study layout – Podru~je istra`ivanja There are many time and motion studies on cable yarding operations, whereby yarding productivity is commonly used as the dependant variable. Most studies show that the three main parameters that influence productivity are mean volume per piece, yarding distance, as well as lateral yarding distance.

In this study the following productivity hypothesis is used: Yarding productivity = f (tree volume, yarding distance, lateral yarding, CHOKER TYPE) A factorial layout is utilized to investigate the productivity hypothesis. Six extraction corridors

2.2 Study sites – Mjesto istra`ivanja The study area is located in the eastern part of the Austrian Alps. The location is characterized by patches of wind thrown trees, whereby the root balls were cut off using a chainsaw. The forest consists almost exclusively of Norway Spruce, with an average extracted tree volume during the study ranging from 0.42 to 0.86 m3 (Table 1). The age varies between 55 and 85 years. As per the study design, six cable corridors were used, with the length of the corridors ranging from 89 to 201 m. Slope gradient ranged from 50 to 60%. Due to the harvest focusing on the extraction of the small areas of wind-thrown trees, timber volume extracted in each corridor varied from 50 to 220 m³.

3. Harvesting system – Sustav pridobivanja drva

Table 1. Stand description Tablica 1. Opis sastojine

Age, year – Dob, god.

Average tree volume, m3 Prosje~ni obujam stabala, m3 Corridor length – Duljina trase `i~are, m Slope – Nagib, % Total volume extracted, m3 Obujam iznesenoga drva, m3 Harvested volume per meter of corridor, m3/m Drvni obujam po metru trase `i~are, m3/m

2

85

Standard choker Standardna spojna kop~a 53

55

Radio-controlled choker Radijski upravljana spojna kop~a 55 65 65

0.86

0.59

0.60

0.42

0.66

0.60

137 52

102 58

140 50

148 60

201 55

89 50

50.2

220.0

76.3

56.7

103.0

76.3

0.37

2.16

0.55

0.38

0.51

0.86

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Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1–9)

Karl Stampfer et al.

divided into elemental work tasks for the yarder system (Table 2) and the choker-setter (Table 3).

For each of the six study replicates, the following response variables, factors and covariates have to be gathered or calculated at the yarding-cycle level (Table 4).

4.2 Heart rate – Bilo

Fig. 1 Radio controlled choker system »Ludwig« Slika 1. Radijski upravljana spojna kop~a »Ludwig« leased by the processor operator through a small control panel. The control panel allows for all the chokers to be released at once, or can be released individually. Each choker is colour-coded for this purpose. To avoid damaging the radio-controlled chokers, the wire rope lengths are not equal.

4. Data collection – Prikupljanje podataka 4.1 Time study – Studij rada i vremena A time and motion data for the yarder system and choker-setter were recorded using the »Latschbacher« portable-time study computers. Work was

A Polar RS 800 G3 portable heart rate monitor is used on the choker-setter during the entire working day, including rest and lunch breaks. It consists of a pericardial heartbeat capturing-transmitting unit on a strap with electrode areas and a receiver-storage unit similar to a digital wristwatch. The heart rate reserve (%HRR) was determined by applying the following formula: %HRR = (HRw–HRr) ⋅ 100/(HRmax–HRr) Where: HRw

Working heart rate: Average number of heart beats per minute, bpm HRmax Maximum heart rate calculated as: 220 – worker age HRr Resting heart rate At the start of the workday the choker-setter sits for a period of 10 minutes. The resting heart rate is then assumed to be the lower of two values; either (a) the average value for this 10 min sitting period, or (b) the minimum heart rate for the whole working day.

Table 2 Work task definitions for yarder system Tablica 2. Radni zadaci definirani za `i~are Work task – Radni zadatak Carriage out – Vo`nja neoptere}enih kolica Hook-up – Podizanje tereta Carriage in – Vo`nja optere}enih kolica Landing – Spu{tanje tereta Release choker – Odvezivanje tovara Manipulation – Premje{tanje tovara Waiting – Zastoji Delays < 15 min – Zastoji < 15 min Delays > 15 minutes – Zastoji > 15 min Miscellaneous – Neodre|eno

Croat. j. for. eng. 31(2010)1

Description – Opis zadatka Carriage movement from the landing out to the choker-setter Kretanje kolica od stovari{ta do kop~a{a Rope is fed out from the carriage until load touches the carriage Spu{tanje u`eta, izvla~enje u`eta te kop~anje i podizanje tereta Carriage movement from the choker-setter back to landing Kretanje kolica od kop~a{a do stovari{ta Lowering load and feeding in and out of the mainline Otpu{tanje kolica i spu{tanje tereta Operator unhooks load, includes getting in and out of the cab Radnik odvezuje teret, {to uklju~uje i izlazak/ulazak u kabinu vozila Moving or processing trees by loader arm – Premje{tanje ili obrada stabala krakom dizalice Operational delay time – Operativno vrijeme ka{njenja Delays shorter than 15 minutes – Zastoji kra}i od 15 min Delays longer than 15 minutes – Zastoji du`i od 15 min Non assignable times – Neodre|eni prekidi rada

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Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1–9)

Table 3 Work task definitions for the choker-setter Tablica 3. Radni zadaci kop~a{a Work task – Radni zadatak Pull rope out – Izvla~enje u`eta Hook-up – Podizanje tovara Lateral in – Postrano privla~enje Load preparation – Priprema tovara Chainsaw work – Rad motornom pilom Waiting – Zastoji Delays < 15 min – Zastoji < 15 min Delays > 15 minutes – Zastoji > 15 min Miscellaneous – Neodre|eno

Description – Opis zadatka Rope is fed out from the carriage until first tree is reached Spu{tanje te izvla~enje u`eta od kolica do najbli`ega oborenoga stabla Load is hooked up – Kop~anje tereta Load pulled back to carriage, until carriage is unclamped from skyline Postrano privla~enje do trase `i~are, dok su kolica nezako~ena Preparing work for the next yarding cycle – Priprema za sljede}i radni ciklus `i~are Operating chainsaw – Rukovanje motornom pilom Operational delay time (choker setter is waiting for carriage) Zastoji u radu (~ekanje kolica) Delays shorter than 15 minutes – Zastoji kra}i od 15 min Delays longer than 15 minutes – Zastoji du`i od 15 min Non assignable times – Neodre|eni prekidi Þ

Analysis of interactions between factors and covariables Þ

Parameter estimation of significant factors and covariables Þ

Regressions analysis Þ

Check model assumptions (residual analysis) Þ

Adjustment of model.

5. Statistical analysis – Statisti~ka analiza Variance analysis was used to quantify the influence of nominal or ordinal-scaled variables. The statistical analysis is carried out using SPSS 15.0 for Windows, with the statistical fundamentals as described in Stampfer (2002). The following analysis strategy was chosen: Þ Estimation of significant effects of covariables and factors and analyzing of their statistical significance (variance analysis) Þ

Evaluation of non-linearity of covariables

The co-variable tree volume is a major component of all production functions, but the relationship between productivity and tree volume is rarely linear. A power factor is used to transform tree volume, whereby Häberle (1984) recommends the estimation

Table 4 Variable Definition for Data Sampling Tablica 4. Prikupljanje podataka

Dependant variables Zavisne varijable

Factor Faktor

Covariates Nezavisna varijabla

4

Cycle Turnus rada Load volume Obujam tovara Productivity Proizvodnost Choker Spojna kop~a Tree volume Obujam stabala Pieces Broj komada Lateral yarding Postrano privla~enje Distance Udaljenost

Total time for one yarding cycle – Vrijeme 1 turnusa rada `i~are

min

Total load volume for each yarding cycle – Ukupni obujam tovara po turnusu rada `i~are

m3 m3 per PSH0

(Load volume/cycle)*60 – (Obujam tovara/radni turnus)*60 (0) standard choker, (1) radio-controlled choker (0) standardna spojna kop~a; (1)radijski upravljana spojna kop~a

2 levels m3

Mean tree volume per load – Srednji obujam stabla u tovaru Number of pieces per load (trees, tops, butts) Broj komada u tovaru (stabla, vrhovi stabala, trupaca) Lateral distance from skyline and felled trees Udaljenost od nosivoga u`eta do sru{enih stabala Distance between tower yarder and stopping position of carriage Udaljenost izme|u pogonskoga ure|aja i mjesta odvezivanja tovara

n m m

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Table 5 Comparison of standard and radio-controlled choker Tablica 5. Usporedba standardne i radijski upravljane spojne kop~e Standard choker – Standardna spojna kop~a Mean Quantile5 Quantile95 Arit. sredina 5. percentil 95. percentil 4.70 2.69 8.13 0.90 0.27 1.70

Cycle – Radni turnus, min Load volume – Obujam tovara, m³ Producitivity, m³/PSH0 Produktivnost, m³/PSH0 Extraction Distance, m Udaljenost privla~enja, m Pieces/turn Broj komada tovara po turnusu, n Tree volume – Obujam stabala, m3 Velocity carriage out, m/sec Brzina kretanja neoptere}enih kolica, m/s Velocity carriage in, m/sec Brzina kretanja optere}enih kolica, m/s

Radio-controlled choker – Radijski upravljana spojna kop~a Mean Quantile5 Quantile95 Arit. sredina 5. percentil 95. percentil 4.42 2.46 7.88 0.81 0.27 1.51

12.5

3.1

26.6

12.1

3.7

25.9

69.2

25

113

59.6

22

122

1.28

1

2

1.26

1

2

0.77

0.20

1.53

0.71

0.19

1.47

2.28

0.56

3.94

1.64

0.46

3.13

2.22

1.03

3.15

2.08

0.86

3.52

of this power value using an iterative procedure to optimize the coefficient of determination and the distribution of the residues.

6. Results – Rezultati Table 5 shows a summary of the results, including the mean and the 5th and 95th quantiles, split out for the standard and radio-controlled choker. Note that carriage velocity is simply the time for the carriage work element divided by the distance.

Overall, the radio-controlled chokers reduced the average cycle from 4.70 to 4.42 minutes. Much of that time saving can be contributed to the landing phase, which reduced from 0.33 to 0.12 minutes. There was no difference in the hook-up phase, and only a slight, but not significant difference in the carriage in.

Interestingly, there was a time increase in the carriage out phase, where the average carriage speed

decreased from 2.3 to 1.6 m/sec. This was attributed to the varied choker lengths used with radio controlled chokers, and that at greater speed they would hit, and sometimes tangle in the trees lining the extraction corridor (Leitner 2009).

Overall, the statistical analysis of in total 936 cycles resulted in the following efficiency model: Efficiency (min/m3) = = 0.96 + 3.49*tree volume – 0.53*Choker

(R2=0.77)

This equation suggests that 77% of the efficiency (min/m3) variance can be explained through the variables tree volume and Choker. We would also expect extraction distance to figure into this resulting equation. This study mainly worked with short extraction distances (average 65.5 m), and therefore this variable had no significant influence on the cycle time. Similarly, the extraction corridors typically used in Austria for whole-tree extraction are only

Table 6 Efficency modell Tablica 6. Model u~inkovitosti Variable – Varijabla Constant – Konstanta Tree Volume – Obujam stabla Choker – Spojna kop~a

Coefficient Koeficijent 0,960 3,495 –0,528

Std. Error Standardna pogre{ka 0,178 0,070 0,203

t-Value t-vrijednost 5,394 49,873 –2,609

Significance, p=0,05 Signifikantnost, p=0,05 0,000 0,000 0,009

R-Squared = 0,774, corrected R-squared = 0,773

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Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1â&#x20AC;&#x201C;9)

Fig. 2 Productivity of the cable yarder system depending on tree volume and choker system Slika 2. Produktivnost rada `i~are ovisno o obujmu stabala i vrsti spojne kop~e 20 meters apart (Stampfer 2002), so there is little lateral extraction and this was also not significant in the final analyses.

Fig. 2 shows the productivity for cable yarding extraction dependent on tree volume and choker system. At an average tree volume of 0.6 mÂł the productivity increased from 7.10 to 7.72 mÂł/PSH15 when using the radio-controlled choker system. This corresponds to an increased productivity of 9%.

For this scenario it is possible to provide an indicative estimation of the pay-back time of the capital cost of the radio-controlled chokers. The difference in productivity is 0.62 m3/PSH15 with an average tree volume of 0.6 m3. For this particular operation the felling and extraction rate was 32 /m3. This suggests that using the radio-controlled chokers would increase revenue by 0.62*32=19.84 per hour. If we simply divide the investment cost of 9000 by 19.84 per hour, then the payback period would be approximately 450 hours (not including depreciation or repair and maintenance costs). By a harvest rate of 25 /m3 the payback period would be 580 hours.

In total 95 hours of heart-rate data was collected from the choker-setter using both manual and radio-controlled chokers. A sustainable work load for a day is defined as the heart rate reserve being not greater than 40% for an 8 hour working day. When using the manual chokers the work load was 40% HRR, and this increased significantly to 44% HRR when using radio-controlled chokers (3). For com-

Fig. 3 Working strain for the choker-setter depending on choker system Slika 3. Fizi~ki napor kop~a{a ovisno o vrsti spojne kop~e 6

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Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1–9)

parison, these values are considerably higher than those measured by Kirk and Sullman (2001). In their study of choker-setter in New Zealand the heart rate reserve ranged from 31.9 to 38.5 % HRR. Fig. 3 shows that the tasks of preparing the load, the radio-controlled activity, fixing the load as well as pulling the mainline the heart rate reserve was considerably higher for the radio-controlled chokers. While some of this additional strain may be attributed to the extra weight of the radio-controlled chokers, this result may also be compounded by the quicker cycle time. Only in the »other« activities of chainsaw work and short delays was the heart-rate higher for the manual chokers.

7. Discussion – Rasprava While this study showed that the radio-controlled chokers can increase productivity, it also highlighted that it may have come at a cost of a higher workload for the choker-setter. It was noted that during the study the choker-setter rarely took a restbreak, and this may be attributed to the exceptionally short extraction distances, as dictated by the study area. This is also evident in the overall productivity model which showed no correlation with extraction distance. Some additional data was captured on a Syncrofalke yarder working in longer extraction corridors. In analysing the data the extraction distance was significant in the productivity model, but with the longer extraction cycles there was no productivity increase associated with the radiocontrolled chokers. The heart rate reserve for the choker-setters exceeded the endurance limit in both instances, but was not statistically different.

The yarder operator in this study was particularly pleased with this new technology and noted not only the simplification of his routine but also the additional safety around the landing. However the choker-setter noted the added difficulty associate with the varied choker lengths. The lengths were varied to avoid the chokers impacting on each other.

This however caused quite wild swinging motions in the carriage out phase, resulting in the operator having to reduce carriage out velocity. He also noted additional maintenance of the chokers associated with the difficulty of wind-throw, as well as the reduced choking effect on smaller tree diameters. He suggested that an additional safety hook may prevent the cap from releasing early. Overall there were only small problems associated with either the radio-control of the yarder and of the chokers.

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Karl Stampfer et al.

8. Conclusion – Zaklju~ci Radio-controlled chokers were studied during cable yarder extraction of wind-thrown trees in the Austrian Alps. The primary benefit associated with these chokers is in the reduced time associated with the landing of the trees (un-hooking), and the corresponding improvement in safety by eliminating this potentially hazardous task. This proved to be correct with the time study showing an overall improvement in productivity. The study also indicated that despite the relatively high investment cost associated with purchasing a set of radio-controlled chokers, that with a productivity improvement of 0.62 m3/PSH15 in the pay-back time is just 480 hours. However this calculation does not include repair and maintenance costs.

To be truly considered a system improvement then the work load on the choker-setter should not increase, or at least not exceed the sustainable work rate for the day. The study however showed that the radio-controlled chokers did significantly increase the heart rate, and it did exceed the sustainable work load.

Acknowledgements – Zahvala The authors would like to thank the following institutions for their support: Austrian Federal Ministry of Agriculture, Forestry Environment and Water Management (Lebensministerium); Austrian Federal Forests (ÖBf), Salzburg Regional Government, Austrian Social Insurance for Occupational Risks (AUVA), the Norwegian Research station and the companies Giritzer and Teufelberger.

9. References – Literatura Baker, S., Sloan, H., Visser, R., 2001: Cable logging in Appalachia and opportunities for automated yarder equipment. In: Proceedings of the 24th Annual Meeting of the Council on Forest Engineering, Appalachian Hardwoods: Managing Change. CD ROM. Wang, J., Wolford, M., McNeel, J. (eds.). July 15 – 19, Snowshoe, West Virginia, USA: 1 – 5.

Biller, C. J., Edward, L. F., 1984: Whole-tree harvesting with a medium capacity cable yarder. Transactions of the ASAE 27(1): 2 – 4.

Häberle, S., 1984: Standardisierung zweidimensionaler Ausgleichsfunktionen über Richt-grad und Richtkonstante.

Forstarchiv 55(6): 220 – 225.

Heinimann, H. R., Stampfer, K., Loschek, J., Caminada, L., 2006: Stand und Entwicklungsmöglichkeiten der Mitteleuropäischen Seilgerätetechnik. Centralblatt für das ge-

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samte Forstwesen (Austrian Journal of Forest Sciences) 123(3): 121 – 139.

Hemphill, C., 1985: Automatic releasing chokers. Logging Industry Research Association (LIRA). Technical Release 7(1): 4.

Huyler, N. K., LeDoux, C. B., 1997: Cycle-time equations for the Koller K300 cable yarder operating on steep slopes in the Northeast. Research Paper NE-705, United States Department of Agriculture, Forest Service. Northeastern Forest Experiment Station, 4 p.

Kirk, P. M., Sullman, M. J. M., 2001: Heart rate strain in cable hauler choker setters in New Zealand logging operations. Applied Ergonomics 32(4): 389 – 398.

Leitner, T., 2009: Funkchoker bei der Seilrückung – Effizienzanalyse und ergonomische Beurteilung. Masters Thesis, Department of Forest and Soil Sciences, University of Natural Resources and Applied Life Sciences Vienna, Austria, 45 p.

MacDonald, A. J., 1990: Bunch yarding with radio-controlled chokers in coastal British Columbia in second growth timber. FRDA report 108. Vancouver, 20 p.

Samset, I., 1985: Winch and Cable Systems, Construction Work and Forest Operation. Dordrecht/Bosten/Lancaster: Martinus Nijhoff / Dr. W. Junk Publishers, 539 p.

Stampfer, K., 1998: Stress and strain effects of forest work in steep terrain. In: Proceedings of the IUFRO/FAO Seminar on Forest Operations in Himalayan Forests with Special Consideration of Ergonomic and Socio-Economic Problems in Thimphu/Bhutan. Heinimann, H. R., Sessions, J., (eds.). http://www.upress.de/abstracts/3-933146-12-7.html.

Kassel University Press, Kassel: 113 – 119.

Stampfer, K., 2002: Optimierung von Holzerntesystemen im Gebirge. Habilitationsschrift, Department of Forest and Soil Sciences, University of Natural Resources and Applied Life Sciences Vienna, Austria, 96 S.

Sa`etak

U~inkovitost i ergonomske prednosti kori{tenja radijski upravljanih spojnih kop~i pri izno{enju drva `i~arama U~inkovito je pridobivanje drva na strmim terenima naj~e{}e povezano s kori{tenjem u`etnih sustava. Tehni~ki razvoj i pobolj{anje sustava rada tijekom posljednjih desetlje}a omogu}ili su u~inkovitiji, dru{tveno prihvatljiviji i ekolo{ki odr`iv na~in kori{tenja {umskih `i~ara. Radijski upravljani ure|aji omogu}uju automatizaciju radnih postupaka pri pridobivanju drva {umskim `i~arama i za radnika na stovari{tu, ali i za radnika kop~a{a u sje~ini.

Spojna kop~a na u`etu `i~are svojevrsna je `i~ana om~a koja slu`i za kop~anje i osiguranje tereta prilikom privla~enja drva {umskom `i~arom. Radnik u sje~ini prilikom kop~anja tereta ru~no postavlja standardne spojne ko~e, a radnik na stovari{tu ru~no ih otklanja s tereta. Tijekom sedamdesetih godina pro{loga stolje}a provedena su prva ispitivanja samootpu{taju}ih mehani~kih spojnih kop~i u Austriji i Norve{koj, ali je njihova primjena bila ograni~ena zbog nepouzdanosti. Izumom prve radijski upravljane spojne kop~e uo~ena je mogu}nost pobolj{anja u~inkovitosti rada, me|utim trebalo je i smanjiti tjelesno optere}enje na radnike jer su uz ve} te{ke terenske uvjete rada i spojne kop~e te`ile preko 4 kg. Tehni~ki razvoj i kori{tenje novih materijala u zadnja dva desetlje}a omogu}ili su stvaranje ~vrstih te lak{ih spojnih kop~i i tako je optere}enje na radnika smanjeno.

Radijski upravljane spojne kop~e tako|er se postavljaju ru~no na teret (kop~anje tereta), ali prednost njihova kori{tenja jest da se mogu upravljati na daljinu odnosno teret se na stovari{tu daljinski odvezuje bez prisutnosti radnika. Uz mogu}u pove}anu sigurnost rada na stovari{tu, prednost radijski upravljanih spojnih kop~i jest skra}ivanje vremena odvezivanja tereta. Me|utim, dodatna masa radijski upravljanih spojnih kop~i mo`e pove}ati optere}enje na kop~a{a na terenu strmoga nagiba. Standardna spojna kop~a te`i oko 0,34 kg, dok je masa radijski upravljane spojne kop~e oko 1,6 kg. Cilj je ergonomije pobolj{ati u~inkovitost sustava rada i radne uvjete, stoga je va`no da pove}anje produktivnosti sustava {umskih `i~ara nije na {tetu pove}anja fizi~koga napora kop~a{a.

Za ocjenu u~inkovitosti i ergomskih pobolj{anja pri kori{tenju radijski upravljanih spojnih kop~i provedeno je istra`ivanje u sastojini obi~ne smreke u isto~nim Alpama u Austriji uz kori{tenje {umske `i~are Wanderfalke.

Prosje~an obujam komada drva bio je 0,4 – 0,86 m3, nagib je terena bio 50 – 60 %, a duljina trase `i~are iznosila je 90 – 200 m. Napravljena je studija rada i vremena uz mjerenje otkucaja srca kop~a{a kao pokazatelja radnoga optere}enja. Rezultati su pokazali da je kori{tenjem radijski upravljanih spojnih kop~i pove}ana produktivnost sustava rada za 9 % pri teretu prosje~noga obujma. Iako su ulaganja pri kupnji radijski upravljanih spojnih kop~i relativno visoka, pove}anje produktivnosti od 0,62 m3/PSH15 omogu}uje povrat ulo`enih sredstava ve} nakon 480 radnih sati. Ovaj izra~un tro{kova ne uklju~uje tro{kove popravka i odr`avanja.

8

Croat. j. for. eng. 31(2010)1

Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding (1–9)

Karl Stampfer et al.

Me|utim, kori{tenjem radijski upravljanih spojnih kop~i pove}ao se tjelesni napor kop~a{a jer se frekvencija srca pod optere}enjem pove}ala oko 40 – 44 %. Uo~eno je da tijekom istra`ivanja kop~a{ rijetko uzima stanku od rada, no to se mo`e pripisati i iznimno kratkim udaljenostima privla~enja drva. Iako je ova studija pokazala da se kori{tenjem radijski upravljanih spojnih kop~i pri privla~enju drva {umskim `i~arama pove}ava produktivnost rada, ta su pove}anja bila na {tetu radnika kop~a{a ~iji je tjelesni napor pri tome porastao.

Klju~ne rije~i: radijski upravljana spojna kop~a, {umske `i~are, kop~a{, ergonomska pobolj{anja

Authors' address – Adresa autorâ: Assoc. Prof. Karl Stampfer, PhD. e-mail: karl.stampfer@boku.ac.at Thomas Leitner, MSc. e-mail: thomas.leitner@boku.ac.at University of Natural Resources and Applied Life Sciences Vienna Department of Forest and Soil Sciences Institute of Forest Engineering Peter Jordan Straße 82 1190 Wien AUSTRIA

Received (Primljeno): March 25, 2010 Accepted (Prihva}eno): May 20, 2010 Croat. j. for. eng. 31(2010)1

Assoc. Prof. Rien Visser, PhD. e-mail: rien.visser@canterbury.ac.nz University of Canterbury College of Engineering Private Bag 4800 Christchurch NEW ZEALAND

9

Original scientific paper – Izvorni znanstveni rad

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation Serena Savelli, Raffaele Cavalli, Sanzio Baldini, Rodolfo Picchio Abstract – Nacrtak In Italy, where conventional forests have a protective rather than productive purpose, some silvicultural operations as first and second thinning could be carried out in an economic way adopting systems based on small scale mechanization. Authors tested a system based on small scale mechanization for bunching and skidding operations, using an All Terrain Vehicle (ATV), a compact, agile and versatile vehicle that adapts well to dense and rather inaccessible forests, such as forests of artificial origin where no kind of intervention, particularly thinning, had ever been carried out. The vehicle was used for bunching, using an electric winch, and for skidding whole trees. The use of the ATV showed that it is a competitive vehicle with both traditional and cutting edge vehicles, performing a traction power average of 313 daN and PHS0 productivity variable from 1.20 to 3.05 td.m.h-1. Such figures confirm how in first thinning, on level ground but also on slopes (max 50%), over distances not exceeding 200 m, the ATV is a perfectly suitable vehicle. Furthermore, the impact of the vehicle on the ground and especially on the shallow soil horizons was negligible and had no effect on tree roots.

Key words: Small scale forestry, All Terrain Vehicle, Thinning, Bunching, Skidding, Winch, Forest utilization

1. Introduction – Uvod First thinning yields low quantities of timber that are often of limited commercial value, making it difficult to get economic revenue (Malinen et al. 2001, Yeo B. J. and Stewart M. 2001, Heikkila et al. 2007).

This explains the worrying tendency to avoid thinning, especially in artificial coniferous forests, and the consequent rise of degradation and instability problems in many forests (Bergström et al. 2007).

Resorting to advanced mechanization would involve substantial investment and above all accurate planning of intervention, not justified by the resulting low productivity in first thinning (Mederski 2006). Conventional forest mechanization is more suitable for third thinning and final cutting and in general it proves to be too demanding or too cumbersome to be applied efficiently in first and second thinning, often causing considerable damage to the trees and to the ground (Heikkila et al. 2007).

According to the latest researches on forest utilization in Italy, especially in coniferous forests, there is a tendency to avoid thinning, mainly for economic Croat. j. for. eng. 31(2010)1

reasons. In fact thinning interventions show high operational costs, in particular when bunching and skidding are concerned, and this is not balanced by the revenue obtained from selling the wood material. The amount of harvested trees in thinning is about 20–40% of the total number of individuals in the forest, which corresponds to 10–25% of the total wood mass. Therefore felling, bunching and skidding operations, in particular during first thinning in high density vegetation, with a shortage of permanent skid roads and where it is quite difficult and/or economically onerous to open temporary skid roads, often present various problems that could be solved in a difficult and expensive way.

Under such forestry circumstances, a test was carried out, featuring an All Terrain Vehicle (ATV), easy to maneuver and highly versatile, that adapts well to the dense and inaccessible woods like most artificial coniferous forests. The vehicle was used for bunching, using an electric winch, and for skidding.

Full Tree System (FTS) was adopted as working method since it guarantees levels of productivity that justify the economics of the intervention, even if

11

S. Savelli et al.

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

it causes a greater loss of organic substance from the forest (Heikkila et al. 2007).

The main objectives of the test were: Þ setting-up of suitable operating methods, with a low environmental impact, for a proper use of the ATV, Þ measuring ATV productivity under different operative conditions, Þ testing possible mechanical and technological improvements in vehicle and working methods.

2. Materials and methods – Materijal i metode The ATV is a multipurpose, versatile vehicle that can be used for moving on trails that are mostly inaccessible to agricultural and forest tractors in various silvicultural operations, from plantation to complementary operations for the final cutting.

The model supplied was suitably adapted to use in operations of bunching and skidding (Fig. 1). The adaptations carried out in collaboration with KL Italia concerned: Þ installation of a Warn electric winch with a pulling force of 12 kN and rope winding speed varying from 2.1 to 7.6 m/min. In ATV for general purpose the winch is mounted on a special plate positioned in front of the vehicle; for the test the winch was applied at the rear of the ATV with the roller fairlead positioned 0.5 m from the ground (as low as possible, to avoid or to limit the vehicle overturning during the winching operation). The winch was equipped with a steel rope with a fiber core, 5 mm diameter, 30 m long and with a minimum breaking strength of 24 kN. The

ATV’s electrical system was made powerful by supplying it with a double battery to guarantee energy supply in case of prolonged use of the winch. Winch controls were positioned both on the handlebar and on the rear of the machine, provided with safety switch, Þ mounting a ROPS on the ATV’s frame, Þ mounting two tool boxes in the front and in the rear of the machine, provided with elastic bands for the secure fastening of the tools, Þ equipping the wheels rim with tire valves protections, Þ assembling a special ballast-holder with the capacity for two ballast, each one with a mass of 20 kg. The rear ballast was due to the extra weight of the rear winch, the double battery and the ROPS. The adapted vehicle overall dimensions were 1.2 m width, 1.9 m length and 1.5 m height, with a total mass (including the ballast) close to 340 kg. The total mass in working conditions, including the driver, a chainsaw, four skidding chains, a hookaroon, a felling lever, a tank for refueling the chainsaw and a toolbox, was up to 445 kg.

The instruments used to acquire the data were: an analogical chronometric table »Minerva« provided with three centesimal chronometers; a tree caliper; an automatic logger’s tape; a clinometer; a laser gauge; a HBM Wägezelle load cell mod. Z7-2 connected to a »CR10C Campbell« data-logger.

A preliminary test was carried out in order to measure the traction features of the ATV. The procedure adopted during the test included: Þ determining the main characteristics of the terrain on which the test was carried out (granulometry, soil type and moisture content) (Table 1), on samples taken with the aid of a corer, Þ carrying out traction tests (OECD, 2007) with two different gears, using »fast« first gear (F) and »slow« first gear (S) (3 replications), with maximum wheel slip of 30%,

Table 1 Characteristics of the soil in Blera area, where the traction tests were carried out Tablica 1. Svojstva tla u podru~ju Blera u kojem su testirane trakcije tla Soil type

Granulometry

Tipovi tala

Fig. 1 ATV adapted for forest use Slika 1. Adaptirani ATV za rad u {umi 12

Clayey Glinovito tlo

Granulometrijski sastav

Moisture, %

Sand, %

Silt, %

Clay, %

Pijesak, %

Prah, %

Glina, %

5

39

56

Vlaga, % 23

Croat. j. for. eng. 31(2010)1

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

S. Savelli et al.

Table 2 Work components of the skidding cycle of the ATV in the two experimental areas Tablica 2. Sastavnice radnoga procesa privla~enja ATV-om u istra`ivanim podru~jima Site Podru~je Casalotti Casalotti Blera Blera

Þ

Method Metode Uphill Uzbrdo Downhill Nizbrdo With winch S vitlom Without winch Bez vitla

Work component – Sastavnice radnoga procesa Approaching and manoeuvring Zauzimanje polo`aja Approaching and manoeuvring Zauzimanje polo`aja Approaching and manoeuvring Zauzimanje polo`aja Approaching and manoeuvring Zauzimanje polo`aja

carrying out traction tests using the »slow« first gear and equipping the vehicle with different ballast: without ballast (W), with front ballast (40 kg) (F), and with front and back ballast (40+53 kg) (FB) (3 replications).

The data related to the pulling force, measured using the load cell and the data-logger, were statistically processed using Kruskal-Wallis non parametric test in so far as data were not distributed normally and with insufficient homogeneity variance.

As observation unit skidding cycle (from the vehicle’s approach to the felling trees and necessary maneuvers to the trees release at the landing) was considered, the working time of each individual work component was recorded using the analogical chronometric table (Kanawaty 1992; Harstela 1991; Berti et al. 1989) (Table 2).

The distances covered by the vehicle to approach the trees and skidding distances were measured by the laser gauge; gradient of the terrain was measured by means of the clinometer.

Wood moisture (w, %) was determined using the thermo-gravimetric method applied on trunk samples. The wood density (r) was calculated as following: mw % rw% = v w% rw%

wood density at a moisture content equal to w, g cm–3 mw% wood mass at a moisture content equal to w, g vw% wood volume at a moisture content equal to w, cm3 Volume of the trunk was calculated from the measurement of the trunk length, using the automatic logger’s tape, and a single diameter measurement on the outside of the bark from the middle of Croat. j. for. eng. 31(2010)1

Tree hooking Vezanje drva Tree hooking Vezanje drva Tree hooking Vezanje drva Tree hooking Vezanje drva

Skidding Privla~enje Skidding Privla~enje Winching and skidding Privitlavanje i privla~enje Skidding Privla~enje

Tree releasing Otpu{tanje drva Tree releasing Otpu{tanje drva Tree releasing Otpu{tanje drva Tree releasing Otpu{tanje drva

the trunk, using the tree caliper, and applying the Huber’s formula: V = L ´ (DOB)2 ´ 0,000000786025 V volume of the trunk, m3 L length of the trunk, cm DOB diameter over bark, cm Mass of the trunk was calculated as following: Mw% = V ´ rw% Mw%

mass of the trunk at a moisture content equal to w, t V volume of the trunk, m3 rw% wood density at a moisture content equal to w, t m-3 Fresh branches and tops were taken from 30 trees randomly chosen at the landing; and their mass was determined by weighting them; their volume was measured by water displacement in a xylometer. The total mass and volume of the trees were calculated adding the mass and volume of the branches and top to those of the trunk.

Mean gross productivity was calculated based on PHS15 (Productive Hour System15) while the mean net productivity was calculated based on PHS0 (Productive Hour System0).

2.1 Characteristics of site and methodology Karakteristike podru~ja istra`ivanja i metode pridobivanja drva Þ

Casalotti experimental area – Podru~je istra`ivanja Casalotti The area is situated within the municipality of Rome; it is covered by a plantation of Pinus eldarica Medw. and the soil is tuffaceous sand (sand 60%; silt 20%; clay 20%). The test plot subjected to thinning extended over 3 ha situated at 40 m a.s.l. and the terrain was characterized by a light roughness and an

13

S. Savelli et al.

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

Fig.2 ATV in uphill skidding Slika 2. ATV tijekom privla~enja drva uzbrdo average gradient of 29% (with maximum value of 47% and a minimum of 19%).

The test plot had an uphill and a downhill landing site with a main road uphill and a secondary road downhill. About half way through its range a firebreak road crosses the area, parallel to the gradient, offering a strip of land 12 m wide and about 120 m long, without trees, used as a further skid road.

Plantation was carried out along the contour according to a planting space of 3x3 m (Fusaro 2003).

No silvicultural treatment was performed before the thinning intervention. The area presented its original density, with bifurcate trees and small clearings due to natural windthrows, which allowed light to penetrate within the branches of standing trees and ensure natural renewal of spontaneous species characteristic of the Mediterranean belt.

The thinning aimed at eliminating dried trees, bifurcated trees, badly formed trees and others by now irrecoverable of the undergrowth. A total of 65 trees were marked and felled using a Stihl MS 260 chainsaw (Table 3). The ATV reared near the butt of the felled trees to hook them with the chain and skid them to the landing where the load was released.

Two skidding directions were adopted according to the tree dimension: large trees were skidded downhill while the smaller ones were skidded uphill (Fig. 2). Þ Blera experimental area – Podru~je istra`ivanja Blera The experimental area is situated in Pian del Pero, within the municipality of Blera; it is covered by plantation of Pinus laricio Poir. over 8 ha, divided into several plots by bare zones or areas covered by thinly scattered vegetation of broadleaf in tree and shrub form, intensely pastured. The soil is clayey (sand 5%; silt 39%; clay 56%). The test plot is located

14

about 200 m a.s.l. and the terrain is characterized by a gradient ranging from 0 to 20%, with stony ground packed by excessive bovine pasture. It is supplied with a secondary trail and a service clearing useful for pasture, used as a landing during the test.

The plantation is 35 years old, developed on degraded pastures; the vegetative condition of the plantation was deteriorated by parasitic attacks extending over the entire surface, which have caused blight and death of numerous trees that remained withered and standing or prostrate on the ground.

The thinning aimed at removal of dried and unwell trees susceptible to becoming hotbeds for the spread of parasites of weakness and easy triggers for fires. Felling and skidding procedures were the same as in the previous experimental area. A total of 185 trees were marked and felled (Table 3).

Using the data obtained from both experimental areas (for Blera area only data from skidding without winch were considered) a regression analysis was applied in order to calculate the equations, which can describe the relations between skidding time and skidding distance and between skidding time and skidding mass.

3. Results and discussion – Rezultati i rasprava 3.1 ATV pulling force – Vu~na sila ATV-a It can be concluded from the statistical analysis that there were significant differences in the values found using the two gear ratios, obtaining the best performance with the »slow« first gear, which revealed an average pulling force of 295.2 daN (Table 4).

Table 3 Mean dendrometric characteristics of trees subjected to thinning Tablica 3. Srednje dimenzije stabala u proredama Parameter Parametri Dbh, cm Prsni promjer, cm Height, m Visina, m Volume, m3 Volumen, m3 Mass, tw98% Masa, tw98% Mass, td.m.

Masa, td.m.

Casalotti

Blera

n.

Av. ± SD.

n.

Av. ± SD.

65

18.4 ± 4.6

185

19.1 ± 5.4

65

10.1 ± 1.6

185

8.5 ± 2.8

65

0.090 ± 0.006

185

0.159 ± 0.011

65

0.10 ± 0.005

185

0.14 ± 0.01

65

0.0 5 ± 0.003

185

0.12 ± 0.01

Croat. j. for. eng. 31(2010)1

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

Table 4 Statistical data of pulling force, differences between »fast« (F) and »slow« (S) first gear Tablica 4. Statisti~ki podaci o sili privla~enja, razlike izme|u »brzohodne« (F) i »sporohodne« (S) prve brzine Parameter – Parametri n Mean ± SD., daN Aritmeti~ka sredina ± Sd., daN St. Err., daN Standardna pogre{ka, daN Kruskal–Wallis p-value Kruskal–Wallis test, p-vrijednost

F Prva sporohodna brzina 120

S Prva brzohodna brzina 120

228.6 ± 63.6 A

295.2 ± 68.0 B

5.8

6.2

0.9861

0.3179

A, B: P<0.05

Considered the statistical analysis of the data obtained from the pulling test with different ballast applications (Table 5) significant difference was obtained only considering the C ballast assembly while no significant difference was recorded between A and B ballast assembly (Table 5).

The ATV was used in subsequent tests using the »slow« first gear and the C ballast assembly.

3.2 Casalotti experimental area – Podru~je istra`ivanja Casalotti The high slope of the ground (in some areas over 40%) and the pulling force performed by the vehicle sometimes required crosscutting of trees with large dimensions, to make skidding easier. Crosscutting was performed by the operator, equipped with chainsaw, both after felling and during skidding, when after the first pulling attempt he realized that the ve-

S. Savelli et al.

hicle was unable to pull the load. Crosscutting was necessary in both skidding directions. Despite substantial differences between the average uphill distances compared to downhill distances, average times for performing the operations were similar (Table 6). In fact the ATV speed when moving downhill was reduced by increasing the load applied.

The larger load skidded in downhill direction affected the productivity, which resulted greater than the one measured in uphill direction (Table 7).

Among the delay times in the work cycle, in both skidding directions there were two salient entries which together stand for over 20% of the total working time (923 min): Þ obstruction at the landing, independent of the vehicle capacity and operator’s ability, but due to inadequate organization of the site (over 15%); Þ jamming of the load during pulling, mainly due to extremely close planting spaces (about 5%).

3.3 Blera experimental area – Podru~je istra`ivanja Blera One of the tests in the Blera area was carried out using the winch for bunching the trees before skidding. The experiment gave good results from the point of view of winch functioning, its correct positioning on the vehicle rear end, operator’s skills in using winch controls. Anyway in the specific context, bunching with the winch could be considered superfluous. In fact due to light load almost exclusively made up of a reduced number of trees that can be pulled by the winch and to the ATV’s agility and maneuverability in positioning at the butt of the trees, the use of the winch was not warranted. Moreover, the time used for winching could be spent in-

Table 5 Statistical data of pulling force, differences between ATV without ballast (W), ATV with front ballast (40 kg) (F) and ATV with front and back ballast (40+53 kg) (FB) Tablica 5. Statisti~ki podaci o vu~noj sili, razlike izme|u ATV-a bez utega (W), s prednjim utegom (40 kg) (F) i s prednjim i stra`njim utegom (40 + 53 kg) (FB) Parameter Parametri n Mean ± SD., daN Aritmeti~ka sredina ± Sd., daN St. Err., daN Standardna pogre{ka, daN Kruskal–Wallis, p-value Kruskal–Wallisov test, p-vrijednost

W Bez utega 117

F S prednjim utegom 159

FB S prednjim i stra`njim utegom 183

299.8 ± 64.9 A

299.7 ± 48.6 A

313.1 ± 42.0 B

6.0

3.9

3.1

0.3951

0.1343

0.4709

A, B: P<0.05

Croat. j. for. eng. 31(2010)1

15

S. Savelli et al.

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

Table 6 Mean values of time, distances and loads during skidding cycles of the ATV in the two experimental areas Tablica 6. Srednje vrijednosti vremena, udaljenosti tovara tijekom turnusa privla~enja ATV-om na istra`ivanim podru~jima

Work component Sastavnice radnoga procesa

Approaching and manoeuvring Zauzimanje polo`aja Tree hooking – Vezanje drva Skidding – Privla~enje drva Tree releasing Otpu{tenje drva

Casalotti Distance, m Udaljenost, m

Blera Time, min Load, td.m.

Time, min Distance, m Load, td.m.

Vrijeme, min Vrijeme, min Udaljenost, m Tovar, td.m.

Tovar, td.m.

With Without With Without With Without Uphill Downhill Uphill Downhill Uphill Downhill winch winch winch winch winch winch Uzbrdo Nizbrdo Uzbrdo Nizbrdo Uzbrdo Nizbrdo S vitlom Bez vitla S vitlom Bez vitla S vitlom Bez vitla 1.17

0.91

92.4

44.7

–

–

1.63

1.50

94.9

77.9

–

–

0.30 1.15

0.31 0.86

– 85.4

– 47.3

– 0.05

– 0.06

3.35 1.41

– 3.49

5.3 94.9

– 77.9

0.30 0.30

– 0.29

0.32

0.31

–

–

–

–

0.69

0.70

–

–

–

–

Table 7 Mean values of PHS15 and PHS0 productivity of skidding in the two experimental areas Tablica 7. Srednje vrijednosti PHS15 i PHS0 produktivnosti privla~enja na istra`ivanim podru~jima Description Prikaz PHS15 productivity, td.m.h-1 PHS15 produktivnost, td.m.h-1 PHS0 productivity, td.m.h-1 PHS0 produktivnost, td.m.h-1

Casalotti Uphill skidding Privla~enje uzbrdo

Downhill skidding Privla~enje nizbrdo

Blera With winch S vitlom

Without winch Bez vitla

0.98

1.28

2.18

2.79

1.09

1.52

2.60

3.05

creasing the number of skidding trips. Therefore, in such conditions of soil and vegetation, it was better to operate without bunching the trees with the winch, achieving an average PHS0 productivity of 3.05 td.m. h-1, rather than bunching first and then skidding, achieving a PHS0 productivity of 2.79 td.m. h-1 (Table 7). The experiment thus highlighted the fact that using the winch is advisable only when trees of small or medium dimensions are available, and they are, however, difficult to be reached by the ATV. As regards the entries of delay times in the work routine, equal to about 8% of the total working time (501 min), there are no substantial differences between those recorded for skidding with ATV and those when bunching was also carried out by winching with the winch. Very high values were nevertheless recorded due to problems with the load and with the loss or jamming of trees during pulling. The reasons are independent of the characteristics of the vehicle and its accessories but they should be traced back rather to the poor technological quality of the trees that were skidded, which gave the load a certain incoherence.

16

Figure 3 Skidding time as function of skidding distance in the two experimental areas Slika 3. Vrijeme privla~enja kao funkcija udaljenosti privla~enja na istra`ivanim podru~jima Croat. j. for. eng. 31(2010)1

Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

S. Savelli et al.

3.4 Regression analysis – Regresijska analiza The regression analysis calculated the equations which can describe the relations between skidding time and skidding distance (Fig. 3). The regression equations were not characterized by a high determination coefficient (R2) so the skidding distance did not seem to influence the skidding time even when the traveling direction was considered.

For such reason skidded mass was considered in relation to skidding time and for describing the relations among these variables regression equations were calculated (Fig. 4). The regression equations were characterized by a fairly high determination coefficient (R2) that was able to point out the dependence degree between the variables. In fact, increasing the skidded mass of the load, the skidding time tended to increase. In Casalotti test the dependence between the variables was proved in both traveling directions.

It can be concluded that in order to achieve high productivity in skidding with the ATV, it is convenient to skid medium sized loads, increasing the characteristics of versatility, easiness of handling and speed of the vehicle in forest, independently of the traveling direction (uphill or downhill).

Comparing the mean value of productivity registered at the two sites (Table 7) it must be taken into consideration that the greater productivity registered in Blera test plot, in particular when skidding

Fig. 4 Skidding time as function of mass skidded per cycle in the two experimental areas (in Casalotti experimental area the wood moisture was 98%, while in Blera the wood moisture was 45%) Slika 4. Vrijeme privla~enja kao funkcija mase skidera (na podru~ju Casalotti vlaga u drvu bila je 98 %, dok je na podru~ju Blera bila 45 %) was carried out without using the winch, was mainly influenced by the gradient of the ground and the

Table 8 Comparison between the average data collected in the present study and those found in the national scientific literature Tablica 8. Usporedba izme|u prikupljenih podataka i podataka prona|enih u znanstvenoj literaturi Distance, m Udaljenost, m

Productivity, td.m. h-1 Produktivnost, td.m. h-1

Trees Vrsta stabala

Ref. Literatura

Mini skidder – Laki skider

110–125

0.65–1.39

Pinus pinaster, Pinus laricio

Baldini et al. 1989 Baldini and Spinelli 1990 Avolio et al. 1989

Mini tractor – Laki traktor, 24 kW

100–300

0.90–1.60

–

Baldini, Donati 1974b

Skidder – Skider, 38 kW

200

1.30

–

Baldini, Donati 1974a

Farm tractor 48 kW and forestry winch Poljoprivredni traktor sa {umskim vitlom, 48 kW

130

1.00

Pinus pinaster

Baldini et al. 1993

Farm tractor 51.5 kW and forestry winch Poljoprivredni traktor sa {umskim vitlom, 51.5 kW

544

0.90–1.10

Pinus nigra

Neri 2004

Forestry tractor – [umski traktor, 44 kW

205

1.51–1.93

Pseudotsuga menziesii, Pinus nigra

Fabiano and Piegai 2007

Mini tractor – Laki traktor, 15 kW

105

0.70–0.77

Pinus laricio

Baldini, Picchio 2001

Farm tractor 60 kW and forestry winch Poljoprivredni traktor sa {umskim vitlom, 60 kW

62–87

1.18

Pinus laricio

Verani, Sperandio 2005

ATV – ATV, 14 kW

47–95

1.20–3.05

Pinus laricio, Pinus eldarica

Present study

Machines – Vrsta stroja

Croat. j. for. eng. 31(2010)1

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Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

characteristics of the harvested trees. In fact in Blera the maximum gradient was 20%, lower than the average gradient in Casalotti (29%). Furthermore in Blera the harvested trees had higher mass and volume, with little dry branches that reduced obstruction during maneuvers between standing trees, while those in Casalotti were green individuals with many, green, persistent branches.

4. Conclusions – Zaklju~ci From the national scientific literature referring exclusively to interventions of first thinning in artificial coniferous plantations, it is possible to assess and compare some of the data recorded in the present study with those reported at similar sites according to type of plantation, type of intervention and utilization systems, where however different systems and levels of mechanization were used (Table 8). The ATV gave such results as to make it competitive with both more traditional and cutting edge vehicles in the agricultural and forestry sector, leading to PHS0 productivity variable from 1.20 to 3.05 td.m.h-1.

The values of productivity confirm that the ATV, in a context of first thinning on level ground but also on sloping ground, over distances not exceeding 200 m, is an ideal vehicle for working in forests where high density does not prevent it from easily entering, hooking up and skidding a load made up of trees of small and medium dimensions.

Based on the data acquired from the test, it can be concluded that: Þ ATV proved to be a suitable vehicle in operations of first thinning in artificial coniferous plantations. Firstly due to its limited size but also to its features of agility and maneuverability which allow the vehicle to move inside the forest, arriving close to the butt of the trees to be hooked, without causing damage neither to the standing trees nor to the ground.

Furthermore no wounds at trees butt were registered because the ATV maneuverability allowed the operator to move even with a full load among trees without causing damage. Þ

ATV achieved higher productivity in skidding if compared with the one obtained by other vehicles as shown in literature; Þ

ATV abilities in skidding over distances shorter than 200 m were superior to those of an agricultural tractor equipped with a forest winch, due to the ease of maneuvering and the higher speed when traveling both unloaded and fully loaded; Þ

ATV pulling force made it particularly suitable to operate with trees of small or medium dimensions such as those obtained in first thinning; Þ

ATV impact on the ground and especially on the shallow horizons was negligible and did

Fig. 5 Impacts on the soil produced by the ATV during skidding Slika 5. Utjecaji na tlo tijekom privla~enja drva ATV-om 18

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Small Scale Mechanization of Thinning in Artificial Coniferous Plantation (11–21)

not affect the tree roots (Fig. 5). The reduced weight and tire characteristics make the vehicle particularly ideal for moving inside the forest.

Acknowledgements – Zahvala The authors would like to thank Dr. E. Fusaro and Dr. S. Verani from CRA in Rome Casalotti, Mr. L. Sandoletti from the Tuscia University and the staff of the Blera Agricultural Municipality for their support.

5. References – Literatura Avolio, S., Baldini, S., Spinelli, R., 1989: Prove di meccanizzazione in diradamenti di pinete artificiali di pino laricio nella Presila di Cosenza. Annali Istituto Sperimentale per la Selvicoltora, 20: 501–547.

Baldini, S., Berti, S., Cutini, A., Mannucci, M., Mercurio, R., Spinelli, R., 1989: Prove sperimentali di primo diradamento in un soprassuolo di pino marittimo (Pinus pinaster Ait.) originato da incendio: aspetti selvicolturali, di utilizzazione e caratteristiche della biomassa. Annali Istituto Sperimentale per la Selvicoltora 20: 385–436.

Baldini, S., Donati, R. 1974a: Rapporto sul trattore da esbosco TA 45. Istituto del Legno, Consiglio Nazionale delle Ricerche, Firenze. Contributi Scientifico Pratici – IRL, XVIII 42: 15–27.

Baldini, S., Donati, R., 1974b: Prove preliminari di esbosco con il trattore leggero Cast 435 L. Istituto del Legno, Consiglio Nazionale delle Ricerche, Firenze. Contributi Scientifico Pratici – IRL, XVIII 44: 39–42.

Baldini, S., Picchio, R., 2001: Primo diradamento con messa a punto di nuove metodologie di lavoro in una pineta dei Cimini. Economia Montana: Linea Ecologica 33 (6): 47–54.

Baldini, S., Pollini, C., Spinelli R., 1993: Agricultural tractor use in wood harvesting. Proceedings of 5th AIGR National Conference. Italian Association of Agricultural Engineering, Maratea, Italy: 213–217.

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Assestamento Forestale, Università degli Studi di Firenze Fascicolo IV: 65.

Cantiani, P., Iorio, G., Pelleri, F., 2005: Effetti di diradamenti in soprassuoli di pino nero (Pettenaio, Perugia). Forest 2(2): 207–216.

Fabiano, F., Piegai, F., 2007: Diradamenti in impianti artificiali di conifere. Sherwood – Foreste ed Alberi Oggi 136: 23–29.

Fusaro, E., 2003: Per la gestione di impiati sperimentali di conifere in ambiente medietarraneo. Prove per l’introduzione di Pinus eldarica in Italia. Economia Montana: Linea Ecologica 35(2): 51–59.

Harstela, P., 1991: Work studies in forestry. Silva Carelica 18: 1–41.

Heikkila, J., Sirén, M., Aijala, J. O., 2007: Management alternatives of energy wood thinning stands. Biomass and Bioenergy 31(5): 255–266.

Jäghagen, K., Lageson, H., 1996: Timber quality after thinning from above and below in stands of Pinus sylvestris.

Scandinavian Journal of Forest Research 11(1–4): 336–342.

Kanawaty, G., 1992: Introduction to work study. Fourth (revised) Edition, International Labour Office, Geneva: 1–494.

Malinen, J., Pesonen, M., Maatta, T., Kajanus, M., 2001: Potential harvest for wood fuels (energy wood) from logging residues and first thinnings in Southern Finland. Biomass and Bioenergy 20(3): 189–196.

Mederski, P. S., 2006: A comparison of harvesting productivity and costs in thinning operations with and without midfield. Forest Ecology and Management 224(3): 286–296.

Neri, F., 2004: Tempi di lavoro e produttività nelle operazioni di abbattimento, allestimento ed esbosco in diradamenti di pino nero nel complesso forestale »Alpe di Catenaria«. Sherwood – Foreste ed Alberi Oggi 100: 5–9.

Niemela, J. 1984: Development of off-road motorcycles and their possibilities in field experiments. Proceeding of the 6th International Mechanization Conference, Rutherford, I. R. Ministry of Agriculture, Fisheries and Food (MAFF), London (United Kingdom). Agricultural Development and Advisory Service Dublin (Ireland): 35–44.

Baldini, S., Spinelli, R., 1990: Miniskidder in Italy. Small Scale Forestry 1: 23–27.

Nordfjell, T., 1990: Small off road vehicles for thinning (mini-forwarders, mini-skidders, SKOGIS, ATV, snow mobiles). Small Scale Forestry 1: 13–22.

Baldini, S., Spinelli, R., 1993: Mini-tractor development for forest utilization. Proceedings of 5th AIGR National Conference. Italian Association of Agricultural Engineering, Maratea, Italy: 87–92.

OECD, 2007: Agricultural Codes and Schemes, Standard code for the official testing of agricultural and forestry tractor performance. Code 2: pp. 61.

Bergström, D., Bergsten, U., Nordfjell, T., Lundmark, T., 2007: Simulation of Geometric Thinning Systems and Their Time Requirements for Young Forests. Silva Fennica 41(1): 137–147.

Berti, S., Piegai, F.,Verani, S., 1989: Manuale d’istruzione per il rilievo dei tempi di lavoro e delle produttività nei lavori forestali. Quaderni dell’Istituto di Tecnologia ed Croat. j. for. eng. 31(2010)1

Picchio, R., Savelli, S., Di Fulvio, F., 2005: Sviluppi nei lavori forestali di ATV e minitrattori. Alberi e Territorio, 2 (10–11): 26–30.

Piegai, F., 1987: Le tecniche di lavoro nei primi diradamenti. Quaderni di Monti e Boschi 3: 33–42.

Spiik, E., 1992: Salvaging wind felled trees with all terrain vehicles. Small Scale Forestry 1: 18–21.

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Spinelli, R., 1995: Sviluppo di un trattore per i diradamenti. Mondo Macchina 2: 22–25.

Spinelli, R., Spinelli, R., 2001: Meccanizzazione in miniatura per i primi diradamenti. L’esperienza svedese. Mondo Macchina 10: 20–22.

Verani, S., Sperandio, G., 2005: Prove di diradamento selettivo meccanizzato su Pino laricio in Calabria. Economia Montana: Linea Ecologica 37(4): 53–57.

Wayman, R. B., North, M., 2007: Initial response of a mixed-conifer understory plant community to burning and thinning restoration treatments. Forest Ecology and Management 239(1–3): 32–44.

Yeo, B. J., Stewart, M., 2001: Thinning Pinus radiata plantations by operator selection: 2. Effect on harvesting productivity. Australian Forestry 64(4): 220–225.

Sa`etak

Privla~enje drva lakom mehanizacijom u proredama crnogori~nih kultura Prve su prorede obilje`ene u prvom redu malom koli~inom posje~ena drvna te niskom komercijalnom vrijednosti drva, s vrlo niskim nov~anim prihodima ili bez njih, {to obja{njava zabrinjavaju}u te`nju za izbjegavanjem proreda, posebno u crnogori~nim kulturama. Izostavljanje proreda mo`e biti uzrok degradacije i nestabilnosti mnogih {umskih sastojina. Polaze}i od takvih okolnosti, provedeno je ovo istra`ivanje radi pronalaska novoga, jeftinijega i jednostavnijega rje{enja za pridobivanja drva u proredama. Vozilo ATV (All Terrain Vehicle), koje je jednostavno za upravljanje i vrlo prilagodljivo na terenu, testirano je u proredama kultura bora. Glavni su ciljevi ovoga istra`ivanja bili: razvoj prikladnih operativnih metoda, odre|ivanje produktivnosti ATV-a u razli~itim uvjetima rada, ispitivanje mogu}ih mehani~kih i tehnolo{kih pobolj{anja vozila i metoda rada.

Istra`ivanje je provedeno uz pomo} modela Kawasaki KLF 300 ATV koji je proizveden za te{ke terenske uvjete, ali nema sportsku namjenu. Glavne su zna~ajke ATV-a visoka vu~na sila, dobra stabilnost i snaga. Karakteristike su motora: obujam od 300 cm3, snaga od 14 kW, okretni moment od 23,5 Nm na 5500 o/min. Prijenosne su karakteristike: poluautomatski mjenja~ s brzim sustavom prijenosa 5 + natra{ke i sporim sustavom prijenosa 5 + natra{ke, najmanja je brzina oko 1 km/h, a najve}a je brzina oko 90 km/h. Na vozilima ATV u suradnji s uvoznikom Kawasaki off-road motocikala za Italiju, KL Italija, izra|ene su odgovaraju}e preinake radi pobolj{anja njihovih karakteristika za skupljanje i privla~enje drva. Preinake su vozila bile sljede}e: ugradnja elektri~noga vitla Warn, ugradnja za{tite od prevrtanja ROPS na okvir ATV-a, ugradnja dviju kutija za alat na prednjem i na stra`njem dijelu vozila, opremanje vijenca kota~a sa za{titnim ventilima za gume, ugradnja posebnoga dr`a~a balasta na prednjem dijelu vozila.

Vozilo se koristilo za skupljanje i privla~enje drva stablovnom metodom na podru~jima: Þ

sastojine bora Pinus eldarica Medw. na podru~ju Casalotti (Rim, sredi{nja Italija) na povr{ini od oko 3 ha, prosje~na nagiba od 29 % i blagih povr{inskih prepreka,

Þ

sastojine crnoga bora Pinus laricio Poir. na podru~ju Blera (Viterbo, sredi{nja Italija), na povr{ini ve}oj od 8 ha, prosje~na nagiba od 5 % i blagih povr{inskih prepreka.

Statisti~ka analiza vrijednosti vu~nih sila ATV-a pokazala je zna~ajne razlike u odnosu vu~ne sile s razli~itim sustavima prijenosa i primijenjenim balastom. Najbolju izvedbu od 313,1 daN (prosje~na vu~na sila) dobivena je u sporohodnoj prvoj brzini i pri balastu od 40 kg na prednjem dijelu vozila i od 53 kg na stra`njem dijelu vozila.

Studijom su rada i vremena utvr|ena ka{njenja u radnom ciklusu od oko 15 % na podru~ju Casalotti pri privla~enju drva uz nagib i niz nagib i oko 16 % pri privitlavanju i privla~enju drva na podru~ju Blera te 8 % pri privla~enju drva na podru~ju Blera. Privu~eno je drvo uzeto u obzir u odnosu na vrijeme privla~enja drva te su za opisivanje odnosa me|u ovim varijablama izra~unate i regresijske jednad`be. Regresijske je jednad`be obilje`io prili~no visok koeficijent determinacije R2 i zna~ajni koeficijent R, koji isti~e stupanj ovisnosti izme|u varijabli, pa je tako s pove}anjem privu~ena drva i vrijeme privla~enja ve}e. Analiza podataka pokazuje da je najve}a produktivnost privla~enja ATV-om pri srednjem optere}enju vozila, bez razlike u smjeru privla~enja uz nagib ili niz nagib. Optere}enje vozila tako|er utje~e na pokretljivost vozila po terenu, lako}u rukovanja i brzinu vozila u {umi. Znanstvena je literatura omogu}ila usporedbu dobivenih rezultata ovoga istra`ivanja s rezultatima drugih istra`ivanja u sli~nim uvjetima, ali pri razli~itim sustavima rada i razinama mehaniziranosti (produktivnost se vozila kretala od 0,65 td.m./h do 2,20 td.m./h). Ovom je usporedbom ustanovljeno da je ATV konkurentno vozilo i tradicionalnim i suvremenijim vozilima u {umarstvu. Produktivnost se ATV-a kretala u rasponu od 1,20 do

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S. Savelli et al.

3,05 td.m./h. Dobivene vrijednosti produktivnosti ATV-a potvr|uju da je ovo vozilo dobar izbor u prvim proredama gustih sastojina na ravnom i blago nagnutom terenu, na udaljenostima ne ve}im od 250 m (udaljenost i podaci prikupljeni u istra`ivanju) jer mjere vozila olak{avaju ulazak u sastojinu, privitlavanje i privla~enje stabala.

Klju~ne rije~i: {umarstvo malih razmjera, vozilo ATV, prorede, skupljanje drva, privla~enje drva, vitlo, iskori{tavanje {uma

Authors' address – Adresa autorâ: Serena Savelli, PhD. e-mail: s.savelli@unitus.it Department of Ecology and Sustainable Economic Development (DECOS) University of Tuscia Largo dell’Università (Blocco E) 01100 Viterbo ITALY Prof. Raffaele Cavalli, PhD. e-mail: raffaele.cavalli@unipd.it Department of Land and Agricultural and Forest Systems (TeSAF) University of Padova Viale dell’Università, 16 35020 Legnaro ITALY

Received (Primljeno): January 07, 2010 Accepted (Prihva}eno): May 14, 2010 Croat. j. for. eng. 31(2010)1

Prof. Sanzio Baldini, PhD. e-mail: baldini@unitus.it Rodolfo Picchio e-mail: r.picchio@unitus.it Department of Environment and Forests (DAF) University of Tuscia Via San Camillo de Lellis 01100 Viterbo ITALY

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Original scientific paper – Izvorni znanstveni rad

Evaluating Repeatability of RTK GPS/GLONASS Near/Under Forest Environment Atinç Pirti, Kutalmiº Gümüº, Halil Erkaya, Ramazan Gürsel Hoºbaº Abstract – Nacrtak Until the mid-1990s, post-processing was the only method available to determine survey-grade positions using GPS. A new method was then introduced called Real-Time Kinematic (RTK). Real Time Kinematic surveying is an advanced form of relative GPS carrier phase surveying in which the base station transmits its raw measurement data to rovers, which then compute a vector baseline from the base station to the rover. RTK GPS shows a really efficient and fast improvement within today’s technological developments. The most important reason for using it is that this technique enables obtaining coordinates instantaneously and in the centimeter level accuracy. This technique is widely used in construction and survey applications because of its above mentioned properties. The aim of this paper is to evaluate the repeatability of RTK measurement accuracy under different satellite configurations near/in forest and unobstructed environments. Testing was performed by using GPS+GLONASS receivers under these conditions, i.e. tall trees forest and unobstructed areas. The obtained results of RTK testing were compared with results of total station surveying as a further quality check. Nevertheless, it appears that RTK measurements under forest environment with 1 cm accuracy cannot be guaranteed on all occasions, since difficult situations may lead to greater errors. These results indicate that integrating RTK GPS/ GLONASS system with total station is favored for surveying under forest environment.

Keywords: RTK GPS/GLONASS, Forest Environment, Total Station, Accuracy

1. Introduction – Uvod The Global Positioning System (GPS) has become a widely used tool for a number of positioning applications. The two GPS carrier signals, L1 and L2, are used extensively for cadastral, topographic and engineering survey applications. The use of the carriers requires the identification of the integer cycle ambiguity inherent in the phase measurement of the carrier signal. Once the integer ambiguities are identified and constrained, the position of a roving receiver can be estimated to an accuracy of, generally, better than two centimeters with respect to a stationary reference receiver. The application of a reference and roving receiver is referred to as differential positioning. There are a number of errors affecting GPS observations that are removed by the differential technique. The residual errors remaining in position Croat. j. for. eng. 31(2010)1

estimates are primarily due to multipath, orbital errors and unmodeled atmospheric errors. It is these influences that limit the use of GPS for high precision applications. For kinematic GPS applications, occupation periods are typically less than one minute, thus limiting the averaging of residual errors.

The use of a data link, to transfer measurements acquired at the reference receiver to the roving receiver, permits the calculation of the rover coordinates at the time of measurement. This survey technique is termed Real Time Kinematic (RTK) and is continuing the revolution that GPS is having in survey practice. The development of RTK enables surveyors to coordinate marks of interest in a rapid and efficient manner. The real time capability enables performing field checks of computed positions, a requirement of cadastral survey legislation in many states and countries. The technique also facilities the

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placing of marks at pre-determined coordinate (Boey et al. 1996, El-Rabbany 2006, Hoffmann-Wellenhof 2001, Schofield 2001, El-Mowafy 2000).

2. Real Time Kinematic (RTK) Technique Metoda kinemati~koga prikupljanja podataka u stvarnom vremenu Precise positioning, using GPS measurements, requires the measurement and processing of the L1 and/or L2 carrier phase signals. The phase of the satellite carriers can be measured to a few millimeters by almost all commercially available GPS receivers. The Cartesian coordinate difference, or baseline, between a stationary reference receiver and other roving receivers can be computed to accuracy suitable for many surveying tasks if the integer cycle ambiguity of the carrier phases can be correctly determined and constrained. Ambiguity resolution techniques, such as known baseline occupations and on-the-fly resolution, in particular, are extremely effective in rapidly identifying the ambiguities. The on-the-fly technique has the advantage of being able to operate successfully while the roving receiver is in motion. In most surveying applications, the position of the receiver while in motion is not of interest. Regardless of this, the most efficient operation occurs when the receiver continuously tracks at least four satellites (and preferably five or six) for the duration of the survey. In the 1980s and early 1990s, the results from all GPS surveys were only available after the survey had been completed and the data post-processed. Post-processing provides robust baseline estimates as all measurements can be manipulated a number of times using least squares estimation techniques. The restrictions of post-processing from the surveyors perspective are that field checks and setouts cannot be performed. Real time kinematic (RTK) surveying introduces a mechanism for transferring the measurements acquired at the reference receiver to the roving receiver as soon as they are collected.

This transfer mechanism, termed the communications link, is usually performed by a form of radio modem. The roving receiver processes the measurements from both receivers and displays the computed position information to the user in the field.

As the position of the roving receiver is required in a timely manner, there is limited time for the rover to pass through previous measurements. Therefore, real time surveying is less robust than post-processing, and however, the accuracy and precision attainable is still suitable for a large number of surveying applications. Real time processing at the roving receiver provides Cartesian coordinates, computed relative to the reference station coordinates. As the

24

reference station coordinates are not always known, the coordinates of the roving receiver are generally presented as a three-dimensional Cartesian coordinate difference from the reference station. Coordinates of points are then propagated using these baselines and knowledge of at least one point with known coordinates. In many countries, the transfer of data from the reference receiver to the rover is regulated by State and Federal communication agencies. To preserve frequency allocation, there are frequency and power restrictions which regulate the use of such communication devices. The carrier phase corrections are transmitted in real time via some (wireless) data link; e.g., via very-high frequency (VHF), HF, or ultra-HF (UHF) radio transmission and applying the OTF (On The Fly) algorithm to fix the related phase ambiguities in small parts of a second. To avoid licensing of radios, low power radios are often used as the output signal is not considered strong enough, by regulation, to cause interference with other signal transmissions. The outcome of this approach is that users are restricted by these radios which often require line of sight operation and a limited range. Although repeater radios can be used to propagate transmissions, most RTK surveys have been performed over small areas ranging from a few hundred meters to, typically, less than five kilometers. With the development of permanent tracking receiver networks, users will expect to survey in real time over significantly larger distances than currently surveyed. The limits of RTK positioning are generally considered to be in the range of ten to fifteen kilometers; however, there is little information available in the literature that defines the level of performance that surveyors can expect under these conditions. RTK surveying is appropriate for any application that requires both high precision and high productivity. Applications such as topography, construction, control point densification, GIS data collection, oil exploration, forest and mining are just a few of the many applications that are good uses of RTK surveying technology (Bilker and Kaartinen 2001, British Columbia, 2005, El-Mowafy 2000, FuhlbrĂźgge 2004, Langley 1998, Pirti 2007, Schofield 2001, Lemmon 1999, Lin 2003).

The GLObal NAvigation Satellite System (GLONASS) is another GPS-like global positioning system. As of October 2009, the GLONASS system consists of 19 satellites, of which 16 are operational, and 3 are undergoing maintenance. The system requires 18 satellites for continuous navigation services covering the entire territory of the Russian Federation, and 24 satellites to provide services worldwide. The availability of GLONASS would bring two significant benefits to geodetic applications of Croat. j. for. eng. 31(2010)1

Evaluating Repeatability of RTK GPS/GLONASS Near/Under Forest Environment (23–33)

global positioning systems. First, the GLONASS solution could be employed as an independent verification of GPS solution to improve quality control.

Second, GPS and GLONASS observations could be combined directly in the process of solution; as a result, the geometry of observed satellites could be enhanced by increasing the number of available satellites. With the recent revitalization of GLONASS, higher precision geodetic GLONASS receivers are brought to market, and GPS/GLONASS receivers have been equipped in some International GNSS Service (IGS) tracking stations all over the world. So it becomes worthwhile to investigate the advantages and disadvantages of combined GPS/GLONASS solution in geodetic application. In order to process combined GPS/GLONASS observations, we should address the problems that arise from the difference in the coordinate systems of the satellite systems, as well as the time and frequency systems employed by GPS and GLONASS. GLONASS satellites transmit signals using FDMA (Frequency Division Multiple Access). GLONASS satellites have available 12 allocated radio frequency carriers in L1 frequency band and 12 carriers in L2 band. Each satellite transmits signals at two frequencies, using one assigned radio frequency carrier in L1 frequency band and one assigned carrier in L2 frequency band (Each satellite transmits a different frequency on L1 (=1602 + Kx0.5625 MHz; KOE[–7.24]) and L2 (=1246 + Kx0.4375 MHz; KOE[–7.24]). Scaling both GLONASS signals observations to a common frequency would not have any sense. While some clock errors can be removed in the double difference procedure, negative side effects will arise simultaneously (Diggelen 1997, ElRabbany 2006, Naesset 2001, Schofield 2001, Kleusberg 1990, El-Mowafy 2000).

As explained above, RTK performs significantly better when tracking both GPS and GLONASS satellites, than when tracking GPS satellites only. Adding GLONASS to GPS improves all aspects of satellite navigation and RTK operation (availability, reliability, stability, time of RTK initialization, and so on). If more satellites are observed using both GPS and GLONASS satellites at the same time, the main advantages of the constellations are (Lemmon 1999): Þ Saving in acquisition time Þ

High accurate precisions Þ

Reduction of values of Position Dilution of Precision (PDOP) and Geometric Dilution of Precision (GDOP). Dilution of Precision (DOP) is an indicator of satellite geometry for a unique constellation of satellites used to determine a position. Positions tagged with a higher Dilution of Precision value generally con-

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stitute poorer measurement results than those tagged with lower Dilution of Precision. There are a variety of Dilution of Precision indicators, such as Geometric Dilution of Precision (it is an indicator of the geometrical strength of a GPS constellation used for a position/ time solution), Position Dilution of Precision (Measure of the geometrical strength of the GPS satellite configuration for 3-D positioning), etc. Þ

Greater productivity in phase of relief especially in cases where natural obstacles (trees, houses, etc.) limit the opening to the sky and therefore the reception of signals.

In order to determine a position in GPS-only mode the receiver must track a minimum of four satellites, representing the four unknowns of 3-D position and time. In combined GPS/GLONASS mode, the receiver must track five satellites, representing the same four previous unknowns and at least one GLONASS satellite to determine the GPS/GLONASS time offset. With the availability of combined GPS/ GLONASS receivers, users have access to a potential 48+ satellite-combined system. With 48+ satellites, performance in urban canyons and other locations with restricted visibility, such as forested areas, improve as more satellites are visible in the non-blocked portions of the sky. A larger satellite constellation also improves real-time carrier phase differential positioning performance (Diggelen 1997, El-Rabbany 2006, Naesset 2001, Schofield 2001, British Columbia, 2005, Fuhlbrügge 2004).

2.1 Limitations and Repeat Observations Ograni~enja i ponavljanje mjerenja Like other precision measurement methods, RTK does have limitations that affect its ability to perform some of the survey tasks discussed above. Being aware of these limitations will ensure successful results from RTK surveys. The limitations of RTK come from the GPS system itself, and not from GPS receivers. GPS depends on receptions of radio signals transmitted by satellites approximately 20 000 km from the earth. Being of relatively high frequency and low power, these signals are not very effective in penetrating through objects that obstruct the line of sight between the satellites and the GPS receiver.

Any object that blocks the path between the GPS receiver and the satellites will be detrimental to the operation of the system. Some objects, such as buildings, will completely block out the satellite signal.

Other objects, such as trees, will partially obstruct or reflect/refract the signal. Reception of GPS signals is very difficult in a heavily forested area. In some

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cases, enough signals can be observed to compute a rough position, but in virtually every case, the signal is not clean enough to produce centimeter-level positions. While enough signals can often be observed to compute a rough GPS position, surveying requires a higher positional accuracy and thus, a larger quantity of clean data. RTK is usually not a tool for surveying in a dense forest, just as an optical total station is not a tool for precisely measuring angles and distances in the dark. This does not mean that RTK is only useful in areas with a wide-open view of the sky. The critical factor is to be able to observe, at any given time, enough satellite signals to accurately and reliably compute a position. In the good parts of the satellite window (the part of the day when most satellites are visible) 5–10 GPS satellites may be visible and available for use in RTK surveying. Accurate and reliable positions can be determined with 5 satellites distributed throughout the sky (not clustered in one part of the sky). Therefore, an obstructed location can be surveyed if at least 5 satellites can be observed. This makes RTK useful in obstructed areas such as along a tree line. Manufacturers are creating new receivers that can use both GPS and GLONASS satellites. GLONASS satellites can also be used for RTK in an integrated approach with GPS satellites in order to increase the number of observed satellites and thus increase accuracy and speed ambiguity resolution. GPS/GLONASS system may be integrated at the user level to improve geometry and positioning accuracy, particularly under poor satellite visibility, such as in forest and urban areas. This advanced RTK systems can be used very effectively and accurately in partially obstructed areas (Diggelen 1997, El-Rabbany 2006, Naesset 2001, Schofield 2001, Hasegawa 2003, Parkinson 1996).

This method involves re-observing features, which had been previously measured using the same method. Ideally the re-observation should occur when there has been a significant change in the satellite constellation and the reference station and rover station have been dismantled and re-assembled. A change in the constellation occurs in varying degrees from one to five hours. It should be noted that satellites have an orbiting period of 12 sidereal hours and constellation configuration repeats itself every sidereal day (1 Solar Day»0.997 Sidereal Day).

If a repeat measurement must be done immediately due to logistical difficulties, it is recommended that the antenna be inverted briefly to lose satellite signal lock. This procedure will reset the ambiguity resolution algorithms and also the signal processing methods which perform multipath effects reduction. Surveying repeat points without re-assembling the reference and rover stations will not provide a means

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for detecting blunders in antenna heights or reference station coordinates (Diggelen 1997, El-Rabbany 2006, Hoffmann-Wellenhof 2001, Schofield 2001, ElMowafy 2000, Lin 2003).

3. Case Study Fieldwork – Terensko istra`ivanje The work was performed in the Campus of Yildiz Technical University Davutpaþa/Esenler, Istanbul, Turkey. The site chosen for the survey is located in the town outskirts, see Fig. 1. Two methods were performed, one using a Topcon Hiper Pro RTK (GPS/GLONASS) field unit and base station with a radio link and another using Topcon GTS 701 total station. The Hiper Pro RTK field unit provides up to 6 kilometers of coverage with the internal radio, 1 Watt transceiver that operates on all European frequencies. HiPer Pro incorporates advanced radio technology called »Free Channel Scan«, which automatically detects disruptive radio interference and changes channels to compensate. The receiver incorporates an internal, Satel UHF transmitter/receiver at 4MHz bandwidth or a UHF receiver at 20 MHz bandwidth, with a 25 kHz channel spacing, and a maximum 1 W power output for data transmission.

The performance specifications of the Topcon Hiper Pro RTK are 10 mm+1.0 ppm for horizontal and 15 mm+1.0 ppm for vertical positioning. They may be degraded in regions of high multipath and high values of the Position of Dilution of Precision (PDOP) as well as during high ionospheric activity. Robust checking procedures are highly recommended in a location of extreme multipath or under dense foliage.

The Topcon HiPer Pro also has the option of dualconstellation (GPS plus GLONASS) tracking, which

Fig. 1 Project area and reference points Slika 1. Podru~je istra`ivanja i referentne to~ke Croat. j. for. eng. 31(2010)1

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provides 40% more satellite coverage than GPS alone. That means downtime due to poor satellite coverage or obstructions is virtually eliminated, and only Topcon brings dual frequency GPS/GLONASS positioning technology to its users.

Two tests were carried out in order to evaluate the performance of the RTK (GPS/GLONASS) method under the unobstructed and obstructed (forest) environments. For this project, two reference points (N101 and N102) were selected in the project area (Davutpaºa region of Istanbul-Turkey, see Fig. 1). A static GPS survey was conducted in order to determine the coordinates of these two reference points.

The measurements in this primary network were performed with at least 4 hours of observation time.

The minimum elevation cut-off angle and the sample rate were 10 degrees and 10 seconds, respectively. All static GPS measurements were carried out using Ashtech Z Max GPS receivers. The data processing and network adjustments were conducted using the Ashtech Solution 2.60 GPS Software. In the adjustment procedure, the ED 50 coordinates of N103 were held fixed (Fig. 1 and Table 1).

The objective of the tests was to assess the RTK GPS/GLONASS achievable accuracy and to check the repeatability of the results under different satellite configurations by using two different reference points (N101 and N102). So, the RTK software and survey performance were evaluated under the unobstructed (the first three points, see Fig. 2) and the forest environments (the other thirteen points), under varying site conditions and where problems due to signal blockage/attenuation were expected, see Fig. 2. The accuracy and repeatability assessment of the RTK survey was carried out by comparing the coordinates of a group of points (16 points). The RTK GPS/GLONASS survey was performed in the sequence of number of points. As explained above,

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Table 1 Coordinates of reference points in the project area Tablica 1. Koordinate referentnih to~aka na podru~ju istra`ivanja Point Y, m Std., m X, m To~ka 101 406930,834 0.002 4543909,912 102 406739,361 0.002 4543871,860 103 407010,897 0.000 4544074,144

Std., m

H, m

Std., m

0.002 65,895 0.004 0.002 71,020 0.004 0.000 80,081 0.000

two different survey methods were used to coordinate a group of 16 points, marked on the ground.

Fig. 2 illustrates the distribution of the tested points.

The maximum distance between the points in the North-South direction was about 30 m. In the EastWest direction the maximum distance was about 100 m.

3.1 RTK Survey Results and Comparisons Terenski rezultati i usporedba mjerenja RTK prijamnikom 3.1.1 Horizontal Accuracy – Horizontalna to~nost To evaluate the RTK GPS/GLONASS repeatability, two independent RTK surveys were carried out using two different reference points, each time occupying all of the test points. The surveys were conducted on consecutive days and at different times of the day from N101 (11 November 2008, 9:00–15:30 h local time (LT)), N102 (12 November 2008, 13:00–19:05 h local time (LT)) with changed satellite configurations to ensure the independence of the results. The reference station N101 was about 0.1 km away from the RTK GPS measurement site, N102 about 0.1 km, see Fig. 1. The satellite visibility was 8–9 and 8–10 (GPS/GLONASS) satellites in open areas and the recorded Position Dilution of Precision average values were 1.5–2.1 and 1.6–2.3 on 11 November 2008 and

Fig. 2 Distribution of test points in the project area Slika 2. Pojavnost to~aka na podru~ju istra`ivanja Croat. j. for. eng. 31(2010)1

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12 November 2008, respectively. However, the satellite visibility was 6–8 and 6–7 (GPS/GLONASS) satellites in the forest areas and recorded Position Dilution of Precision average values between 3.1–4.2 and 3.7–4.8 on 11 November 2008 and 12 November 2008, respectively. It is obvious that Position Dilution of Precision value has direct influence on positioning error. A total of 32 point observations for the 16 test points were obtained over the two days. In the analysis step, the differences of the coordinates of the 16 test points obtained from N101, N102 were calculated. Fig. 3 shows the differences and their means and standard deviations for the 16 points.

The analysis of the test for the RTK GPS/GLONASS results shows that the discrepancies of the horizontal coordinates were a few mm to 4 cm. The discrepancies of the height coordinates were a few centimeters to about 10 cm (Fig. 3). The first three points (Points 1, 2 and 3) have clear lines of sight to the satellites because of the unobstructed area, see Fig. 2.

The results for the Points 1, 2 and 3 in Fig. 3 (first 3 data points on left) show that the RTK positioning was good in general. As shown in Fig. 3, the average differences of the RTK system were less than 0.5 cm for horizontal plane coordinates, and less than 1 cm along the vertical direction for these three points. On the other hand, the forest (trees) caused severe obstruction of the sky for the other thirteen points in the project area, see Fig. 2. Even though several satellites were shaded by the trees, they could still be tracked by the receiver. As explained above, 6–8 satellites were visible in this period. The Position Dilution of Precision value was between 3.1 and 4.8 for both tests. All of the results for thirteen points also show that tree canopies and forests were harmful to RTK positioning, as they frequently blocked the signals of the satellites and affected radio signals. Thus, even with the presence of good satellite windows, signal blockage due to tree canopies or forest could be considered as the main problem affecting the use of RTK GPS/GLONASS in forest areas. Due to the above reasons, the RTK GPS/GLONASS measurements on thirteen points took a very long time on two days. The ambiguity resolution time was approximately 300–350 minutes for these thirteen points on both days. The horizontal coordinate differences of these 13 points were greater than 2 cm between the first and the second day of RTK GPS measurements (Fig. 3). The maximum differences of the horizontal coordinates are about 3–4 cm. In these thirteen points, ambiguity is fixed and the number of satellite is 6–8 but signal attenuation occurs because of the forest area. Using the dual-frequency carrier phase as main observable and fixing the initial integer phase ambiguities, i.e. a fixed solution,

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gave the best accuracy. However, searching for fixed solutions increased the risk of large individual positional errors due to false fixed solutions.

3.1.2 Vertical Accuracy – Vertikalna to~nost GPS is based on a three dimensional coordinate system. This means that both the horizontal (X, Y) and vertical coordinates (H) are required for the points. The required accuracy of the heights at the points depends on the task. To apply the RTK method under forest, it is necessary to achieve a high horizontal accuracy, whereas for the determination of the H coordinate it is sufficient to use the height from a topographical map. All 16 points are also used for technical tasks, which often require a high accuracy of the H coordinate. Fig. 3 also demonstrates that the greatest differences have occurred in the vertical coordinates of 13 points between each day’s measurements. The height component was however less consistent as to horizontal components, and sometimes differed up to 10 cm at the same point between the two RTK sessions. For the other three points, height differences were as little as a few centimeters. In these experiments, the baselines were typically quite short where the effect of the troposphere was less significant.

3.2 Comparison of RTK GPS Measurement Results with Total Station Measurement Results – Usporedba mjerenja prijamnikom RTK i geodetskom mjernom stanicom In the second step of the test, the 16 point coordinates were determined by a total station (Topcon GTS-701). The N102 reference point and the N101 reference point were taken as control points for the total station surveys (Fig. 1). Both terrestrial and RTK GPS measurements were carried out in an increasing sequence of identification number of points. In order to compute the coordinates of the 16 points, horizontal directions, zenith angles and slope distances were recorded with Topcon GTS–701 (angle accuracy: ±2’’, distance measurement accuracy: 2 mm+2 ppm). In order to minimize the errors introduced by curvature and refraction, the sight distances should be less than 300 meters. The maximum distance was about 200 meters in this study.

The total station measurements were carried out in two faces (FL, FR) since the manufacturer’s accuracy specification refers to the mean of measurements taken in two faces. Three reflector/tripod sets were available. Tripods were used for the reflector set-ups on the points. Each point was observed using a reflector mounted on a tripod, which was optically plumbed over the point. Point heights were determined by subtracting the reflector heights above the Croat. j. for. eng. 31(2010)1

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Fig. 3 Comparison of coordinates of test points using N101, N102 as reference points Slika 3. Usporedba koordinata ispitivanih to~aka kori{tenjem referentih to~aka N101 i N102 Croat. j. for. eng. 31(2010)1

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points. The test points (16) were observed from one reference point N102. It took about 60 minutes to survey the 16 points from N102.

In the test, total station survey was carried out to check the performance of the RTK GPS/GLONASS survey. RTK GPS/GLONASS can be used depending on the project requirements, location, and other factors. The RTK surveying method seems to be the most suitable in unobstructed areas. This is mainly because of its ease of use and availability of the results in the field. Inaccessible locations or obstructed areas can be surveyed with an integrated system such as a GPS+GLONASS/total station. RTK does not handle all kinds of survey problems as other survey techniques do. RTK is only suitable for environments with reasonably good GPS/GLONASS tracking conditions (limited obstructions, multipath, and radio frequency noise) and with reliable communication from the GPS/GLONASS base to the rover (Diggelen 1997).

In this test, the accuracy and repeatability assessment of the RTK survey was carried out by comparing the coordinates of a group of points (16 points) obtained from N101, N102 with the coordinates determined by the total station from N102, see Fig. 4.

The term »geodetic« is used to loosely refer to bearings and coordinates related to the European Datum 1950 (ED50). The total station survey was reduced onto the ED50 system for the comparison of the two methods, as the RTK measurements were all made on the ED50 system. Fig. 4 gives the coordinate differences between the RTK and the traditional survey.

Orthometric heights (ED50) were used for the total station survey.

The comparison of the results of the RTK GPS/ GLONASS and total station surveys shows that the variations were greater in height and smaller in horizontal coordinates. Fig. 4 shows the differences and their means and standard deviations for the 16 points.

The standard deviation of the horizontal coordinate differences was about 1–2 cm on the first day and 1–2 cm on the second day. The standard deviation of the height differences was 3.3 cm on the first day, 2.8 cm on the second day. As shown in Fig. 4, the two-day mean differences between the RTK survey and the total station survey were less than 2 cm for the horizontal coordinates and less than 3 cm for the vertical coordinates. Again, the largest variations in horizontal and vertical coordinates were recorded for thirteen points in the project area, see Fig. 4. The variations were about 2–5 cm in the X–Y coordinates and about 3–10 cm in the H coordinates. We are likely to encounter significant differences in the horizontal and vertical coordinates at difficult points. Our results are consistent with those of many other groups

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Fig. 4 Comparison of coordinates of 16 points in the project area between total station and two days of RTK GPS (N101 (1st day), N102 (2nd day)) surveys Slika 4. Usporedba prostornih koordinata snimljenih geodetskom mjernom stanicom i prijamnikom RTK 30

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that made similar tests. The horizontal and vertical accuracy in clear and obstructed areas discussed in this paper are in agreement with those of the other authors.

Except for the changing geometry of satellites within a forest environment (thirteen points, see Fig. 2), the results clearly show that the RTK technique is a stable method and a cm level of accuracy is generally obtainable under various operational conditions.

The RTK method is problem free particularly where a centimeter level horizontal accuracy is required.

This study shows that the technique of RTK GPS/ GLONASS is able to deliver results equivalent to those expected from a traditional total station survey. Another conclusion is that the RTK method does not give a vertical accuracy, which can be used for those types of leveling tasks that are usually carried out by geometric leveling (millimeter accuracy).

4. Conclusions and Discussion – Zaklju~ci i rasprava Dense forest canopy posed a significant physical barrier to quality GPS signal reception. The signals are noisier, weaker and therefore more likely to be subject to multipath and diffraction. Therefore, there are still some problems about the difficulties to receive the signal in close area such as the area covered with dense forest. In the forest environment there is a problem of a very high attenuation of the satellite signals, which are hardly sufficient for normal operation of the GPS receiver. The trees and foliage cause mainly dispersion of the radio signal, and reflected signals have usually so little energy that they can not have any serious influence on GPS receiver performance as multipath signals. The surveyor should be aware that positions may not be accurate despite quality indicators pointing to good solutions. In cases of signal blockages, such as in forest areas, RTK needs to be aided by a total station.

For the unobstructed environment considered in this experiment, the average differences between the RTK and the total station surveys were less than 1 cm for the horizontal plane coordinates and less than 2 cm in vertical coordinates. For thirteen points (multipath environment) the horizontal plane coordinates differed up to 5 cm and the heights approximately 10 cm. So, special attention should be paid to the selection of the working area. It appears that in difficult environments, measurements with 1 cm accuracy cannot be guaranteed in all situations.

In this paper, we have shown that RTK GPS/ GLONASS can be used for forest surveying, although a common obstacle, the sky blockage, hinders its full effectiveness. But this problem can be Croat. j. for. eng. 31(2010)1

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overcome if supplemented by conventional survey techniques. Despite the accuracy problems in obstructed areas, the RTK method is a very efficient replacement for difficult total station survey situations. In this study, the RTK GPS/GLONASS method using only one reference point required approximately 6–6.5 hours to survey 16 points. The total station survey of 16 points required approximately 1 hour in the field. The RTK GPS/GLONASS required about 10 minutes in the office for data transfer and processing. The total station data required about 15 minutes in the office for transfer and processing.

The RTK technique has one major advantage over the other methods; positions are directly determined on the terrain and many independent ambiguity values might be resolved, allowing redundancy of RTK positioning. It is clear that the time of RTK positioning in forest conditions should be chosen during the best satellite constellation and in the season when there are no leaves on trees. When total station methods are used in the projects one can meet with some difficulties such as lack of sight between two control points, inaccessible angle points and loss of time. Projects carried out using total station methods employ much more people. RTK GPS surveying method has some advantages over traditional surveying methods in that RTK GPS needs no sight between control points. In addition, RTK GPS can be managed by only one person and whole surveying process can be carried out by using only one reference point, depending on the quality of the radio transmitter and the distance between the points and reference station. Another advantage of RTK GPS is that the coordinates of the points can be determined in national coordinate reference frame in real time. The only handicap of the system is that the RTK GPS requires at least five satellites simultaneously and an open sky view. RTK GPS has the capability to operate the system in every weather condition.

In the near future, after GLONASS and GALILEO (Galileo is a global navigation satellite system (GNSS) currently being built by the European Union (EU) and European Space Agency (ESA). The 3.4 billion project is an alternative and complementary to the U.S. Global Positioning System (GPS) and the Russian GLONASS. On 30 November 2007 the 27 EU transportation ministers involved reached an agreement that it should be operational by 2013) are fully deployed, the satellite positioning systems will have different dimensions. Finally, the improvements in GALILEO, GLONASS and modernized GPS will increase the signals for the GNSS user community.

This will bring numerous benefits for applications requiring fast and accurate positioning. The combination of GPS with GLONASS and/or GALILEO

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provides more robust, accurate and cost effective studies as compared with GPS only. GLONASS and GALILEO are proposed to be fully deployed; more than 80 satellites will cover the world (El-Rabbany 2006, URL1).

5. References – Literatura Bilker, M., Kaartinen, H., 2001: The Quality of Real Time Kinematic GPS Positioning, Reports of the Finnish Geodetic Institute, Kirkonummi: 25 pp.

Boey, S. S., Coombe, L. J., Gerdan, G. P., Hill, C. D., 1996: Assessing the Accuracy of Real Time Kinematic GPS Positions for the Purposes of Cadastral Surveying. The Australian Surveyor 41(2): 109–120.

British Columbia, 2005: Guidelines for GPS RTK surveys, including operating within a Municipal Active Control System Area – Release 1.0, Province of British Columbia, Ministry of Sustainable Resource Management, Base Mapping & Geomatic Services, Victoria, BC, May, pp. 1–18.

Diggelen, V. F., 1997: GPS and GPS+GLONASS RTK, New Product Descriptions Session, ION-GPS 97, Kansas City, MO. El-Mowafy, A., 2000: Performance Analysis of the RTK Technique in an Urban Environment. The Australian Surveyor 45(1): 47–54.

El-Rabbany, A., 2006: Introduction to GPS: The Global Positioning System, Second Edition, Artech House, pp. 159–160.

Fuhlbrügge, J. H., 2004: Untersuchungen zur Prüfung von GPS-Echzeitsystemen als Beitrag zur Qualitätssicherung im Vermessungwesen, Inaugural-Dissertation zur Erlangung des akademischen Grades Doktor-Ingenieur, Mitteilungen aus den Geodätischen Instituten der Rheinischen Friedrich-Wilhems-Universität Bonn, Nr. 91, Bonn, 142 pp.

Hasegawa, H., Yoshimura, T., 2003: Application of dualfrequency GPS receivers for static surveying under tree canopies. Journal of Forest Research 8(2): 103–110.

Hoffmann-Wellenhof, B., Lichtenegger, H., Collins J., 2001: GPS Theory and Practice 5th revised edition, SpringerVerlag Wien–New York: 382 pp.

Kleusberg, A., 1990: Comparing GPS and GLONASS. GPS World 1(6): 52–54.

Langley, R., 1998: RTK GPS, GPS World 9(9): 70–76.

Lemmon, T. R., Gerdan G. P., 1999: The Influence of the Number of Satellites on the Accuracy of RTK GPS Positions. The Australian Surveyor 44(1): 64–70.

Lin, L. S., 2003: Integrating of GPS RTK and Total Station for Land Surveying of Urban Region, 1st Taipei International Conference on Digital Earth, Chinese Cultural University, Taipei, Taiwan, November 18–19, and No. C1–12: 1–10.

Næsset, E., 2001: Effects of differential single and dual-frequency GPS and GLONASS Observations on Point Accuracy under forest canopies. Photogrammetric Engineering and Remote Sensing 67(9): 1021–1026.

Parkinson, B. W., Spilker, J. J., 1996: Global Positioning System, Theory and Applications, Vol. 1, Chapter 15, Foliage Attenuation for Land Mobile Users, Stanford University and Telecom, Stanford, California, pp. 569–583.

Pirti, A., 2007: Performance Analysis of the Real Time Kinematic GPS (RTK GPS) Technique in a Highway Project (Stake-out), Survey Review, Vol. 39, No. 303, January.

Schofield, W., 2001: Engineering Surveying: Theory and examination problems for students, 5th Edition, Butterworth–Heinemann, 521 pp.

URL1: http://www.mapmiddleeast.org/magazine/2005/ sep–oct/future_3.htm

Sa`etak

Ocjenjivanje ponovljivosti sustava RTK GPS/GLONASS u neposrednoj blizini {umskoga podru~ja Do sredine 1990-ih korekcija je prostornih podataka (post-processing) bila jedina metoda za utvr|ivanje prostornih polo`aja kori{tenjem ure|aja GPS (Global Positioning System), potom je uvedena nova metoda naziva kinemati~ka metoda u stvarnom vremenu (Real-Time Kinematic). Kinemati~ka metoda u stvarnom vremenu napredni je oblik relativnoga ure|aja GPS kojom se podaci s bazne stanice prenose na rover, koji potom vektorski izra~unava liniju od bazne stanice do rovera. Metoda RTK omogu}uje prijenos podataka s bazne stanice na rover ~im su podaci prikupljeni. Ovaj mehanizam za prijenos podataka, nazvan komunikacijska veza (communications link), naj~e{}e je radijski modem. Rover zaprima podatke obaju prijamnika i prikazuje izra~unati trenuta~ni polo`aj korisnika na terenu.

Polo`aj je rovera potrebno dobiti u odre|enom vremenskom roku, pa je i obrada prija{njih mjerenja polo`aja ote`ana. Mjerenja su u stvarnom vremenu stoga prikladnija od same korekcije prostornih podataka, a to~nost je mjerenja i dalje prikladna za ve}inu korisnika.

Obrada podataka u stvarnom vremenu omogu}uje roveru pribavljanje Kartezijevih koordinata, izra~unatih relativno prema koordinatama referentne stanice. RTK GPS pokazuje u~inkovitost i brz napredak u dana{njem razvoju tehnologija, najvi{e zbog mogu}nosti pribavljanja koordinata trenuta~no i na razini centimetarske to~nosti.

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Ova se metoda najvi{e koristi u terenskim istra`ivanjima zbog spomenutih svojstava. Prednosti mjerenja RTK nad korekcijom prostornih podataka kinemati~kih i »stani-kreni« mjerenja (stop-and-go) jesu smanjenje dodatnoga rada u uredu te mogu}nost provjere na terenu tijekom snimanja. Kori{tenjem RTK-a podaci se mogu odmah obra|ivati preko GIS-a, {to pove}ava ukupnu u~inkovitost.

Cilj je ovoga rada ocijeniti to~nost mjerenja RTK pri razli~itim satelitskim konfiguracijama u blizini {ume, u {umi te u neometanom okru`enju. Ispitivanje je provedeno pomo}u prijamnika GPS + GLONASS (Global Navigation Satellite System) pod tim uvjetima, tj. na podru~jima pokrivenima {umom i u neometanom okru`enju.

Dostupnost sustava GLONASS donijet }e dvije zna~ajne koristi geodetskim programima globalnoga sustava pozicioniranja. Prvo, GLONASS bi mogao neovisno potvrditi to~nost GPS-a i drugo, mjerenja pomo}u GPS-a i GLONASS-a mogu se izravno upotrijebiti kao rezultat jer je geometrija satelita pobolj{ana pove}anjem broja dostupnih satelita. Sateliti GLONASS mogu se koristiti za RTK zajedno sa satelitima GPS kako bi se pove}ao ukupan broj dostupnih satelita, a samim tim }e se pove}ati to~nost te brzina pri neodre|enim rezolucijama. Sustavi GPS i GLONASS mogu se uklopiti radi pobolj{anja geometrije i to~nosti pozicioniranja u prostoru, osobito pri slaboj vidljivosti satelita kao {to je ~esto u {umskim i urbanim podru~jima. Ti se napredni sustavi RTK mogu koristiti vrlo u~inkovito i to~no u djelomi~no nedostupnim podru~jima.

Kao {to je prije obja{njeno, sustav RTK snima polo`aje mnogo bolje kada koristi i satelite GPS i GLONASS, nego samo satelite GPS. Kori{tenje satelita GLONASS zajedno sa satelitima GPS pobolj{ava dostupnost, pouzdanost, stabilnost, inicijalizacijsko vrijeme sustava RTK i tako dalje. Uz dostupnost prijamnika GPS i GLONASS korisnici imaju omogu}en pristup sustavu od 48+ satelita. Takav sustav omogu}uje vidljivost u urbanim podru~jima i drugim podru~jima ograni~ene vidljivosti, kao {to su {umske povr{ine, jer ve}a koli~ina satelita pobolj{ava pozicioniranje u prostoru. Ve}a dostupnost vidljivih satelita tako|er pobolj{ava diferenciranje faze nosa~a u realnom vremenu (real-time carrier phase differential).

Gust {umski sklop je zna~ajna fizi~ka prepreka za kvalitetan prijam signala GPS-a. Signal je slabiji te je stoga vi{e vjerojatno da }e dolaziti do pogre{aka u pozicioniranju, zato jo{ uvijek postoje te{ko}e u zaprimanju signala u podru~jima pokrivenima gustom {umom. U {umi se javlja problem prigu{enja signala jer drve}e uzrokuje raspr{ivanje uglavnom radijskoga signala, dok odbijanje signala zbog njegove male energije nema ve}i utjecaj na rad prijamnika GPS, kao {to to ima vi{estazni signal. Korisnik ure|aja mora biti svjestan da snimljeni polo`aji mo`da i nisu to~ni, unato~ pokazateljima koji upu}uju na suprotno. U slu~aju nedostupnosti signala, kao {to je ~esto u {umskim podru~jima, sustav RTK treba biti potpomognut radom totalne stanice.

U ovom je radu prikazano da se sustav RTK GPS/GLONASS mo`e koristiti za izmjere u {umskim podru~jima, ali se zbog ograni~ene vidljivosti satelita mora nadopuniti uobi~ajenim tehnikama istra`ivanja. Unato~ problemima u to~nosti mjerenja, metoda RTK vrlo je u~inkovita zamjena za kori{tenje totalnih stanica pri terenskim istra`ivanjima. Dobiveni su rezultati mjerenja RTK uspore|eni s rezultatima mjerenja totalnom stanicom radi provjere kakvo}e izmjerenih podataka. Ipak, ~ini se da to~nost mjerenja RTK od 1 cm u {umskom okru`enju nije zajam~ena u svim prilikama, {to }e u kona~nici dovesti do ve}ih pogre{aka. Dobiveni rezultati istra`ivanja pokazuju da je integracija sustava RTK GPS/GLONASS s totalnom stanicom najpo`eljniji sustav za mjerenja u {umskim podru~jima.

Klju~ne rije~i: RTK GPS/GLONASS, {umsko podru~je, totalna stanica, to~nost

Authors' address – Adresa autorâ:

Received (Primljeno): May 12, 2009 Accepted (Prihva}eno): December 15, 2009 Croat. j. for. eng. 31(2010)1

Assoc. Prof. Atinç Pirti, PhD. e-mail: atinc@yildiz.edu.tr Kutalmiº Gümüº, BSc. e-mail: kgumus@yildiz.edu.tr Assoc. Prof. Halil Erkaya, PhD. e-mail: herkaya@yildiz.edu.tr Asst. Prof. Ramazan Gürsel Hoºbaº, PhD. e-mail: ghosbas@yildiz.edu.tr Department of Geodesy and Photogrammetry Engineering 34349 Beºiktaº – Istanbul TURKEY

33

Original scientific paper – Izvorni znanstveni rad

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil Compaction in Soft Terrains Yuri Gerasimov, Vasily Katarov Abstract – Nacrtak A study of the effect of bogie wheel track and slash reinforcement on the sinkage (as rut depth) and soil compaction (as bulk density) of silt loam soil was carried out in spring and autumn at two harvesting sites in Russia. A Ponsse ELK forwarder loaded with 16 m3 of timber, fitted and unfitted with bogie tracks, was repeatedly driven on forest soil for 1–10 passes. The degree of sinkage and soil compaction was measured at two soil moisture contents: moist (W = 80%) and wet (W = 93%) after each pass. A John Deere 1410 forwarder loaded with 16 m3 of timber, and fitted and unfitted with bogie tracks, was driven on forest soil covering a 15 kg/m2 slash layer for 1–10 passes. The degree of soil compaction was measured at moist soil (moisture content W = 88%). The results indicated that on forest silt loam soil the bogie track decreases sinkage in comparison with a conventional wheel with a tire: the maximum rut depths reached were 0.48 m vs. 0.71 m (–0.23 m) on wet and 0.22 m vs. 0.40 m (–0.18 m) on moist soils by the 10th pass (160 m3 of extracted timber), respectively. The track influence on soil compaction varied and was mixed. Bulk density increased up to 1.30 g/cm3 vs. 1.24 g/ cm3 (+0.06 g/cm3) on moist soil and it was almost the same on wet soil by the 10th pass, respectively. The slash reinforcement constrained rut-forming and soil compaction after all forwarder passes. Cubic regressions between average rut depth and bulk density and cumulative volume of extracted timber were derived for forest silt loam soil with different moisture contents. Bogie track and particularly slash reinforcement are necessary for environmentally sensitive wood harvesting by the CTL system on soft soils.

Keywords: CTL, forwarder, rut depth, bulk density, slash, bogie track, Russia

1. Introduction – Uvod The fully mechanized cut-to-length (CTL) wood harvesting system, based on a single-grip harvester and a wheel forwarder, has become more common in Russia (Gerasimov et al. 2008). Many reasons are given for this statement, including reduction in labor requirements, work safety risks, environmental damage, and landing areas in comparison with the traditional tree-length (TL) and full-tree (FT) systems. In many specific conditions, the CTL system is cost competitive with tree-length harvesting. However, some of the advantages have not been sufficiently defined for specific conditions, particularly related to cross-country ability and ecology.

Mechanized CTL harvesting in thinning and clear felling and extraction are potentially damaging Croat. j. for. eng. 31(2010)1

to harvesting sites, as the operations are conducted under all weather conditions involving predominantly heavy machinery (Zeleke et al. 2007). Fig. 1 illustrates the extreme condition of rut formation on the forest soil that was made by multiple passages of a loaded forwarder in Russia. Extreme machine sinkage has a direct influence on the productivity, fuel consumption, and cost of harvesting operations, and leads to site disturbance and soil damage. This is especially true in areas with soft soils in spring and autumn, where some options are used to improve the operational capability of the existing CTL system, such as »bogie track« and »slash reinforcement« (Fig. 2).

A forwarder equipped with a bogie track has a low average ground pressure on soil in comparison with a conventional wheel with a tire. Consequently,

35

Yuri Gerasimov and Vasily Katarov

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35â&#x20AC;&#x201C;45)

Fig. 1 Typical rut on silt loam soil caused by forwarder passes Slika 1. Karakteristi~an kolotrag forvardera na pjeskovitoj ilova~i the external motion resistance on soft terrain is much lower, and drive speed and efficiency are more improved. In addition, sinkage and soil compaction are reduced and damage to the ecology (terrain) is minimized (Batelaan 1998).

CTL harvesters spread limbs and tops in their path as they process stems. Trails covered with slash

avoided rut formation, showed lower decreases in porosity, and saturated hydraulic conductivity (Eliason and Wästerlund 2007, McMahon and Evanson 1994, Jakobsen and Moore 1981). The effect of a residue layer in reducing soil compaction was considered positive, although a statistically significant influence was not found (McDonald and Seixas 1997).

Fig. 2 Bogie track and slash reinforcement Slika 2. Polugusjenica i zastor granjevine na tlu 36

Croat. j. for. eng. 31(2010)1

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Yuri Gerasimov and Vasily Katarov

Table 1 Description of harvesting sites and machinery Tablica 1. Opis mjesta istra`ivanja i strojeva Cut block Region Sje~ina Pokrajina ha

Karelia

Tver

Tree species Vrste drve}a %

16.5

Pine – Bor, 30 Spruce – Smreka, 30 Birch and Aspen – Breza i trepetljika, 60

21.2

Spruce – Smreka, 30 Birch – Breza, 20 Aspen – Trepetljika, 50

Stock Zaliha m3/ha

162

252

Stem volume Obujam stabla m3

0.215

0.314

Loading, per test pass Optere}enje po testnom prolasku

Forwarder Forvarder 6WD Ponsse ELK Carrying capacity – Nosivost: 13 t Tyres – Gume: front – prednje 700/55 ´ 34, back – stra`nje 710/45 ´ 26,5, pressure – tlak punjenja guma: 350 kPa Ground clearance – Klirens vozila: 0.67 m Tracks – Polugusjenice: 700 ´ 26.5 8WD John Deere 1410 Carrying capacity – Nosivost: 14 t Tyres – Gume: front and back – prednje i stra`nje 710/45 ´ 26,5, pressure – tlak punjenja guma: 350 kPa Ground clearance – Klirens vozila: 0.605 m Tracks – Polugusjenice: »Olofsfors«700 ´ 26.5

13 tons (16 m3 timber) 13 tona (16 m3 drva)

13 tons (16 m3 timber) 13 tona (16 m3 drva)

Table 2 Description of treatments Tablica 2. Opis ina~ica pokusa No. Oznaka

Region Pokrajina

KW93

Karelia

KT93

Karelia

KW80

Karelia

KT80

Karelia

TW88

Tver

TT88

Tver

Ground contact device Vozni sustav stroja Conventional wheel with tire Kota~ s gumom Bogie track Polugusjenica Conventional wheel with tire Kota~ s gumom Bogie track Polugusjenica Conventional wheel with tire Kota~ s gumom Bogie track Polugusjenica

Surface Povr{ina Forest soil [umsko tlo Forest soil [umsko tlo Forest soil [umsko tlo Forest soil [umsko tlo Slash mat* Zastor granja* Slash mat* Zastor granja*

Moisture content, % No. of test plots Sadr`aj vlage, % Broj pokusnih ploha

Number of samples Veli~ina uzorka Rut depth Soil – Tlo Dubina kolotraga

93

11

20

44

93

11

20

44

80

11

20

44

80

11

20

44

88

11

–

44

88

11

–

44

*14.2–15.6 kg/m3

Several studies (Bygdén et al. 2003, [u{njar et al. 2006, Sakai et al. 2008, Syunev et al. 2009) have shown an advantage when covering extraction trails with slash or using a bogie track. However, the benefits have not been clearly defined for specific conditions. This research was intended to investigate how a bogie track and slash reinforcement influence the sinkage and compaction of prevalent silt loam soil, and how Croat. j. for. eng. 31(2010)1

these effects interact with forwarder travel and moisture content.

2. Methods and data – Metode i podaci The first study experiment on the effect of a bogie track was carried out at a cutting area near the town of Medvezhegorsk in the Republic of Karelia, Rus-

37

Yuri Gerasimov and Vasily Katarov

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

sia. The tests were conducted in late spring 2009. The forwarder used in the study was a Ponsse ELK.The second study experiment on the effect of slash was carried out at a cutting area near the town of Vyshny Volochek in the Tver region, Russia. The tests were conducted in early autumn 2009. The forwarder used in the study was a John Deere 1410.

Descriptions of the cutting areas and machinery are shown in Table 1. Soils in the test areas were silt loams, and moisture contents were 80%, 88%, and 93%. The forwarders were equipped with 710/45 ´ 26.5 tires inflated to 350 kPa, and passed over the plots in one direction at about 4 km/h. One pass was defined as one trip of the loaded machine with a loaded weight of 13 tons of timber.

Six linear test plots (30 m ´ 4 m) were installed in cutting areas. On each plot, measurement points were set as follows: left rail, right rail, and cutting strips (monitoring of natural properties). The rut depth was measured in both right and left rails and the average value of the trail depth was calculated.

To determine the soil compaction, the organic layer was removed from each measurement point and soil samples were taken using a soil hammer. Soil samples were taken at measurement points according to a standardized methodology (GOST 12071–84) from the surface layer of 0–5 cm in the central zone of the skid trails. The soil samples were delivered to the soil laboratory in airtight packaging and weighed with electronic balances with a resolution of 0.01 g.

The bulk density of the soil samples was also determined.

The following six treatments (combination of ground contact devices, surfaces, moisture contents W; Table 2) with one to ten passes were assigned to each of the plots within each block: Þ forest soil, conventional wheel with tire, W = 93%, (KW93) Þ Þ

forest soil, bogie conventional track 700´26.5, W = 93%, (KT93)

forest soil, conventional wheel with tire, W = 80%, (KW80) Þ forest soil, bogie track, W = 80%, (KT80) Þ 15 kg/m2 slash layer, conventional wheel with tire, W = 88%, (TW88), and Þ 15 kg/m2 slash layer, bogie combination track 700´26.5, W = 88%, (TT88).

The choice of the number of passes equal to 10 was made based on a previous study that indicated that the most compaction occurs within the first trips (Syunev et al. 2009).

The number of rut depth and soil samples for each treatment was 20 and 44, respectively. The

38

choice of number of soil samples after each pass for each treatment, equal to 4, was made based on the prior study experiment and calculation as follows (Redkin 1988): N³

s 2 z2 r2 p2

(1)

Where: r mean of bulk density (r = 1.13 g/cm3), s quadratic deviation of bulk density (s = 0.047 g/cm3), z certainty index (z = 1.96 for a 95% confidence interval), p measurement accuracy (p = 0.05 for a 95% confidence interval).

The slash was collected from a mixed stand in Tver region (see Table 1, Fig. 3) that was clear-cut by a harvester. Ten linear test plots (1–1.5 m) were installed along the skid trails. On each plot, the slash was gathered and weighed with spring balances with a resolution of 0.1 kg. The weight of heavy pieces (over 10 kg) was calculated using log diameter, length and tree species density. Slash densities for these conditions were about 15 kg/m2, slash mat thickness varied from 15 to 20 cm, comparable to the values in other studies (for example, Galaktionov et al. 2009). There was a large variation in limb size including 18% of large limbs (more than 10 cm diameter) and 15% of tops remaining after processing (Fig. 3).

Soil compaction was analyzed using changes in bulk density following traffic. The soil samples for bulk density were collected with a soil hammer with a 4 cm diameter and 4 cm length rings. Oven-dry weight (12 hours at 105 °C) was used to express bulk density as weight/unit volume (g/cm3) and moisture content.

Four samples were taken for bulk density at each of 11 depths in the soil profile (0–5 cm) for a total of 44 from each plot. This sampling regime was applied to both pre-treatments (a total of 20 samples per plot). In addition to changes in soil physical properties, soil disturbance was quantified using measures of rut depth at the midpoint of each plot. All samples were collected after passes, with undisturbed samples collected from the rut centre line.

Soil type was classified according to the Russian soil-classification standard (GOST 25100-95) based on the plasticity index and the relative proportions of the various soil separates as described by the classes of soil texture. The name of the textural soil class was adapted to the USDA system using the Glossary of Terms in Soil Science (1976).

Croat. j. for. eng. 31(2010)1

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Yuri Gerasimov and Vasily Katarov

Fig. 3 Brush mat, before and after consolidation Slika 3. Zastor granjevine prije i nakon prolaska vozila The data were statistically processed using statistical and regression analyses with SPSS 15.0 for Windows.

3. Results – Rezultati 3.1 Impact of a bogie track – Utjecaj polugusjenica The average soil water contents at the study time were 93% for the wet plots and 80% for the moist plots, without slash reinforcement. Pre- and posttreatment rut depth and bulk density means are shown in Table 3 (KW93, KT93, KW80, and KT80).

In the case of a wheel with a tire on wet soil (KW93), the initial soil bulk density value was 1.06 g/cm3. The post-treatment bulk density increased slightly up to 1.15–1.17 g/cm 3 during the first 5 passes. It was slightly lower by the 6 th and 7th passes at 1.11 g/cm 3, and grew again and stabilized by the 9th and 10 th passes at 1.14 g/cm 3. The rut depth increased rapidly up to 0.71 m, particularly during the first 5 passes. The forwarder clearance (0.67 m) was exceeded on the 9th pass.

In the case of a bogie track on wet soil (KT93) the initial soil bulk density was 1.03 g/cm3. The post-treatment bulk density increased slightly up to 1.17 g/cm3 within the first 6 passes. Then it decreased slightly by the 7th to 10th passes and stabiCroat. j. for. eng. 31(2010)1

lized at 1.13 g/cm3. The rut depth increased evenly up to 0.48 m, particularly during the first 3 passes.

The forwarder clearance was not exceeded.

In the case of a wheel with a tire on moist soil (KW80) the initial soil bulk density was 1.06 g/cm3.

The post-treatment bulk density increased up to 1.33 g/cm3 within the first 4 passes. Then it decreased slightly by the 5th to 7th passes at 1.29 g/cm3, decreased again, and stabilized by the 8th to 10th passes at 1.24 g/cm3. The rut depth increased rapidly up to 0.40 m, particularly during the first 7 passes. The forwarder clearance was not exceeded.

In the case of a bogie track on moist soil (KT80) the initial soil bulk density was 1.05 g/cm3. The post-treatment bulk density increased slightly up to 1.33 g/cm3 within the first 6 passes. Then it decreased slightly by the 7th to 10th passes and stabilized at 1.30 g/cm3. The rut depth increased evenly up to 0.22 m. The forwarder clearance was not exceeded.

3.2 Impact of a slash layer – Utjecaj zastora granjevine The average soil water content during the study time was 88%, and the slash had a density of 15 kg/m2.

Pre- and post-treatment bulk density means are shown in Table 3 (TW88 and TT88). The initial soil bulk density was 1.06 g/cm3.

39

Yuri Gerasimov and Vasily Katarov

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Table 3 Rut depths and bulk density changes by treatments and passes Tablica 3. Promjene dubine kolotraga i prirodne gusto}e tla po ina~icama pokusa i broju prolazaka

Bulk density – Prirodna gusto}a tla, g/cm3 Change, % of initial density Promjena, % od po~etne gusto}e tla Rut depth – Dubina kolotraga, m Change, % of forwarder clearance Promjena, % od klirensa forvardera g/cm3

Bulk density – Prirodna gusto}a tla, Change, % of initial density Promjena, % od po~etne gusto}e tla Rut depth – Dubina kolotraga, m Change, % of forwarder clearance Promjena, % od klirensa forvardera

g/cm3

0

1

1.06

1.10

3 KW93 1.13 1.17

3.4

6.6

0.16

1.03

Bulk density – Prirodna gusto}a tla, Change, % of initial density Promjena, % od po~etne gusto}e tla Rut depth – Dubina kolotraga, m Change, % of forwarder clearance Promjena, % od klirensa forvardera

1.06

Bulk density – Prirodna gusto}a tla, g/cm3 Change, % of initial density Promjena, % od po~etne gusto}e tla Rut depth – Dubina kolotraga, m Change, % of forwarder clearance Promjena, % od klirensa forvardera

1.05

g/cm3

Bulk density – Prirodna gusto}a tla, Change, % of initial density Promjena, % od po~etne gusto}e tla

g/cm3

Bulk density – Prirodna gusto}a tla, Change, % of initial density Promjena, % od po~etne gusto}e tla

1.06

1.06

2

7

8

9

10

1.15

1.15

1.13

1.11

1.11

1.14

1.14

9.2

8.2

7.8

6.0

4.8

4.4

7.2

6.8

0.26

0.34

0.41

0.47

0.53

0.58

0.62

0.67

0.71

24

39

51

61

70

79

87

93

100

106

1.07

KT93 1.12 1.15

1.17

1.17

1.17

1.16

1.15

1.13

1.13

3.8

7.6

10.6

11.5

11.8

11.4

10.8

10.5

8.5

8.7

0.09

0.14

0.22

0.23

0.28

0.32

0.36

0.39

0.44

0.48

13

21

33

34

42

48

54

58

66

72

1.14

KW80 1.21 1.27

1.33

1.27

1.29

1.27

1.22

1.24

1.24

6.8

12.8

16.8

20.6

16.5

17.7

16.8

13.0

14.7

14.8

0.08

0.11

0.15

0.21

0.24

0.27

0.33

0.34

0.35

0.40

12

16

22

31

36

40

49

51

52

60

1.10

1.16

KT80 1.23

1.26

1.29

1.33

1.32

1.27

1.31

1.30

4.4

9.2

14.7

16.1

18.4

20.6

20.1

17.4

19.5

19.0

0.05

0.08

0.1

0.13

0.13

0.15

0.16

0.18

0.20

0.22

12

16

22

31

36

40

49

51

52

60

1.07

TW88 1.08 1.08

1.09

1.10

1.11

1.11

1.11

1.11

1.12

0.5

1.6

2.0

2.2

3.4

4.1

4.3

4.5

4.5

5.2

1.08

TT88 1.08 1.08

1.09

1.09

1.09

1.10

1.10

1.10

1.11

1.4

1.8

2.3

2.2

2.6

3.4

3.7

3.5

4.4

In the case of a conventional wheel (TW88) the post-treatment bulk density increased slightly up to 1.10 g/cm3 within the first 5 passes. Then it stabilized by the 6th to 10th passes at 1.11 g/cm3. Ruts were not detected (less than 0.05 m).

40

Number of pass – Broj prolazaka 4 5 6

1.9

In the case of a bogie track (TT88) the post-treatment bulk density increased slightly up to 1.08 g/cm3 within the first pass. It then stabilized at 1.10–1.11 g/cm3. Ruts were not detected (less than 0.05 m).

Croat. j. for. eng. 31(2010)1

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Bulk density and rut depth trend curves based on the obtained data were constructed using a Cubic regression model with R-square values of 0.99 for depths and 0.80–0.99 for density: D=b0+b1·v+b2·v2+b3·v3

(2)

Where: D rut depth (m) or bulk density (g/cm3), v cumulative volume of extracted timber (m3), b0, b1, b2, b3 coefficients of equation.

The coefficients of the Cubic model as a function of treatment conditions (moisture contents, tracks, slash) are presented in Table 4. Fig. 4 shows the relationship between extracted timber volume and rut depth. Fig. 5 shows the relationship between extracted timber volume and bulk density.

Yuri Gerasimov and Vasily Katarov

3.3 Soil classification – Razredba tla The results of soil classification are presented in Table 5. The difference between initial mass and total mass of samples did not exceed 0.05 g (less than 0.05%). The relative proportions of the various soil separates in the studied soils corresponded to the silt loam class.

4. Discussion and conclusions – Rasprava i zaklju~ci Regarding soil compaction, the CTL system met the ecological requirements for this type of forest soil (1.4 g/cm3) within the bounds of the experimental design. However, an increase in bulk density was found in all treatments at the silt loam soil surface (0

Table 4 Coefficients of the Cubic model as a function of treatment conditions Tablica 4. Koeficijenti modela procjene dubine kolotraga i gusto}e tla No. Oznaka KW93 KT93 KW80 KT80 TW88 TT88

Bulk density – Prirodna gusto}a tla b0 1.054 1.023 1.046 1.038 1.060 1.064

b1 0.004 0.004 0.008 0.005 0.001 0.001

b2 –5.53E-05 –3.49E-05 –8.20E-05 –2.80E-05 –7.97E-07 –6.15E-06

Rut depth – Dubina kolotraga b3 2.02E-07 8.30E-08 2.44E-07 3.65E-08 -3.32E-09 2.28E-08

b0 0.052 0.020 0.033 0.012

b1 0.007 0.005 0.003 0.003

b2 –3.22E-05 –2.457E-05 –2.96E-06 –2.01E-05

b3 7.45E-08 8.16E-08 3.088E-08 7.07E-08

Fig. 4 Relationship between extracted timber volume and bulk density Slika 4. Ovisnost obujma izve`enoga drva i prirodne gusto}e tla Croat. j. for. eng. 31(2010)1

41

Yuri Gerasimov and Vasily Katarov

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Fig. 5 Relationship between extracted timber volume and rut depth Slika 5. Ovisnost obujma izve`enoga drva i dubine kolotraga Table 5 Distribution of samples by size of soil particles Tablica 5. Granulometrijski sastav tla po ina~icama pokusa

Sand particles – ^estice pijeska Silt particles – ^estice praha Clay particles – ^estice gline Plasticity index – Indeks plasti~nosti Grain size distribution – Granulometrijski sastav

Prior Prije 27 55 18 11.0

Soil particles percentage – Postotni udio ~estica tla Treatments – Ina~ice pokusa KW93 KT93 KW93 KT93 TW88 31 32 35 35 30 53 51 50 50 52 16 17 15 15 18 10.3 10.6 9.7 9.5 11.1 Silt loam – Pjeskovita ilova~a

to 5 cm depth). The magnitude of the increase was a function of the number of passes, the slash/track presence, and the moisture content. In comparison with conventional wheel treatments, bogie track treatments showed that compaction of wet and moist silt loam held irregularly. The formation of a compacted zone under the traction element, helped by reinforcement of forest soil roots, took place in the first phase. With the increasing number of passes the compacted zone deepened and partly collapsed, and there was a lateral bulging of the soil. Then there was a slight increase in density, due to the formation of secondary hardened zones. The results for slash reinforcement treatments indicated that a layer of slash mitigated the effect of a single forwarder pass and subsequent passes. The bulk density did not change considerably. The increased bulk density for the forest soils was nearly 10% of that of the slash

42

TT88 29 53 18 11.2

covered soils. Also, the present of the combination »slash + track« made no apparent difference within the bounds of the experimental design.

Regarding sinkage, the CTL system with a conventional wheel did not meet the ecological requirements for thinning (rut depth should be less than 0.15 m). Moreover, rut depth reached the forwarder clearance of the machine (0.67 m) on wet soil. The results of bogie track treatments showed that the rut depth did not meet the ecological requirements for thinning (0.15 m) particularly on wet soil, but was within the forwarder clearance of the machine. In the slash treatments the rut depth changed only slightly.

All mechanized harvesting systems (TL, FT, CTL) applied in Russia cause different kinds of negative environmental impacts. When applied on sandy or Croat. j. for. eng. 31(2010)1

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

sandy loam soils, all mechanized systems demonstrated almost the same impacts on the soil (Syunev et al. 2009). However the proportion of sandy soils is small in Russian forests in comparison with loams and clays. On loams and clays, the TL and FT systems, unlike the CTL system, resulted in significant soil compaction, but at the same time formed almost no track. Over 50% of the harvesting sites in Russia are on wet and soft soil (Ananyev et al. 2005). Therefore, the application of the CTL system has to be improved in order to reduce rut formation in most common soils. Hence, the associated CTL machine ground contact devices and slash layer must be suitably adapted for specific harvesting sites, based on terrain classification criteria. The adaptation requires a further study of the effects of the ground contact device (tire or track) and size of slash layer, the induced ground contact pressure, and the physical characteristics of the slash layer that are affected during soil deformation, which negatively influence the CTL system cross-country ability and environmental impact.

Acknowledgements – Zahvala The work was carried out for the project »Wood Harvesting and Logistics«, financed by the European Union through the Finnish Funding Agency for Technology and Innovation (TEKES), and for the project »Creation of Planning System of Forest Infrastructure and Management for Industrial and Energy Wood Transportation«, funded by the Federal Agency of Science and Innovation of the Russian Federation (ROSNAUKA). We would like to thank Prof. Timo Karjalainen from Finnish Forest Research Institute for useful suggestions.

5. References – Literatura Ananjev, V., Asikainen, A., Välkky, E., Gerasimov, Y., Demin, K., Sikanen, L., Syunev, V., Khljustov, V., Tyukina, O., Shirnin, Y., 2005: Thinnings in northwest of Russia. METLA, Joensuu: 150 p.

Batelaan, J., 1998: Development of an all terrain vehicle suspension with an efficient, oval track. Journal of Terramechanics 35(4): 209–223.

Bygdén, G., Eliasson, L., Wästerlund, I., 2003: Rut depth, soil compaction and rolling resistance when using bogie tracks. Journal of Terramechanics 40(3): 179–190.

Galaktionov, O., Kuznetsov, A., Piskunov, M., 2009: The properties of flooring made of logging waste products and

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ground condition of skidding road. Proceedings of Petrozavodsk State University. Natural and Engineering Science 101(7): 90–95.

Gerasimov, Y., Sokolov, A., Karjalainen, T., 2008: GIS-based decision-support program for planning and analyzing short-wood transport in Russia. Croatian Journal of Forest Engineering 29(2): 163–175.

Gerasimov, Y., Syunev, V., 1998: Ecological optimization of logging technology and machinery. University of Joensuu, Joensuu: 170 p.

Glossary of Terms in Soil Science, 1976: Canada Department of Agriculture, Research Branch, Ottawa, Publication 1459: 44 p.

GOST 12071-84, 1984: Soils: sample collection, packing, transportation and storage. State Standard, Moscow.

GOST 25100-95, 1995: Classification of soils. State Standard, Moscow.

Eliasson, L., Wästerlund, I., 2007: Effects of slash reinforcement of strip roads on rutting and soil compaction on a moist fine-grained soil. Forest Ecology and Management 252(1–3): 118–123.

Jakobsen, B. F., Moore, G. A., 1981: Effects of two types of skidders and of a slash cover on soil compaction by logging of mountain ash. Australian Journal of Forest Research 11: 247–255.

McDonald, T. P., Seixas, F., 1997: Effect of slash on forwarder soil compaction. International Journal of Forest Engineering 8(2): 15–26.

McMahon, S., Evanson, T., 1994: The effect of slash cover in reducing soil compaction resulting from vehicle passage.

LIRO Report 19(1): 1–8.

Redkin, A. K., 1988: Basic foundation of modeling and optimization of wood harvesting. Moscow, Timber Industry: 256 p.

Sakai, H., Nordfjell, T., Suadicani, K., Talbot B., Bøllehuus, E., 2008: Soil compaction on forest soils from different kinds of tires and tracks and possibility of accurate estimate. Croatian Journal of Forest Engineering 29(1): 15–27.

Syunev, V., Sokolov, A., Konovalov, A., Katarov, V., Seliverstov, A., Gerasimov, Y., Karvinen, S., Välkky, E., 2009: Comparison of wood harvesting methods in the Republic of Karelia. Working Papers of the Finnish Forest Research Institute 120: 117 p.

Zeleke, G., Owende, P. M. O., Kanali, C. L., Ward, S. M., 2007: Predicting the pressure–sinkage characteristics of two forest sites in Ireland using in situ soil mechanical properties. Biosystems Engineering 97(2): 267–281. [u{njar, M., Horvat, D., [e{elj, J., 2006: Soil compaction in timber skidding in winter conditions. Croatian Journal of Forest Engineering 27(1): 3–15.

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Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35â&#x20AC;&#x201C;45)

Sa`etak

Utjecaj polugusjenica i zastora granjevine na dubinu kolotraga i zbijanje tla pri izvo`enju drva forvarderom na tlu ograni~ene nosivosti Istra`ivanje je provedeno u prolje}e i jesen na dvama lokalitetima u Rusiji radi utvr|ivanja utjecaja polugusjenica na bogi kota~ima i zastora granjevine pri vi{ekratnim prolascima forvardera na deformaciju i zbijanje pjeskovito-ilovastoga tla. Istra`ivanje utjecaja polugusjenica na bogi kota~ima forvardera Ponsse ELK (sl. 1) na zbijanje tla provedeno je u kasno prolje}e 2009. godine na podru~ju Karelije. Idu}a su ispitivanja zbijanja tla pri prolasku forvardera John Deere 1410 uz polaganje granjevine uzdu` kolotraga provedena u oblasti Tver u jesen iste godine. Opisi sje~ina i kori{tenih forvardera dani su u tablici 1 i na slici 2. Tlo je po granulometrijskom sastavu odgovaralo pjeskovitoj ilova~i, sa sadr`ajem vlage 80 %, 88 % i 93 %, a gusto}a polagane granjevine na tlo je iznosila 15 kg/m2. Na ukupno {est pokusnih ploha vozilo je prolazilo 1 do 10 puta, na svakoj su plohi uzeta 44 uzorka tla (tablica 2).

Zbijanje je tla istra`ivano zbog promjena u gusto}i tla i dubini kolotraga nastalim zbog vi{ekratnoga prolaska vozila. Prilikom uzimanja uzoraka tla (valjci promjera 4 cm te duljine 4 cm) gornji (organski) sloj tla je uklonjen te su uzorci tla va|eni s dubine 0 do 5 cm na sredini kolotraga. Hermeti~ki zatvoreni valjci dostavljeni su u laboratorij gdje im je mjerena masa prije i nakon su{enja (na 105 °C) radi izra~unavanja vlage, odnosno gusto}e tla.

Dubina je kolotraga iskazana kao srednja vrijednost mjerenja lijevoga i desnoga kolotraga voznoga sustava (kota~, polugusjenica) forvardera.

Istra`ivanje je na podru~ju Karelije pokazalo da je prosje~na mokrina tla iznosila 93 % kod mokroga tla te 80 % na vla`nom tlu bez postavljanja zastora granjevine na tlo. Promjene dubine kolotraga te gusto}e tla zbog vi{ekratnoga prolaska vozila prikazane su u tablici 3 (KW93, KT93, KW80 i KT80).

U slu~aju prolaska vozila bez polugusjenica na mokrom tlu (KW93) po~etna je gusto}a tla iznosila 1,06 g/cm3, a nakon prvih 5 prolazaka forvardera porasla je od 1,15 do 1,17 g/cm3. Daljim prolascima forvardera (6. i 7. prolazak) uo~en je pad gusto}e tla na vrijednost od 1,11 g/cm3, a dodatnim prolascima gusto}a je tla neznatno ponovno rasla te se ujedna~ila na 1,11â&#x20AC;&#x201C;1,14 g/cm3. Dubina se kolotraga naglo pove}avala tijekom prvih 5 prolazaka forvardera, a nadi{la je klirens forvardera (0,67 m) nakon 9. prolaska vozila.

U slu~aju prolaska vozila s polugusjenicama na mokrom tlu (KT93) po~etna je gusto}a tla bila 1,03 g/cm3, dok je gusto}a nakon 6 prolazaka vozila porasla do 1,17 g/cm3. Zatim je gusto}a tla bila ne{to manja pri 7. do 10. prolasku vozila te se ujedna~ila na vrijednosti od 1,13 g/cm3. Dubina se kolotraga ravnomjerno pove}avala do 0,48 m, osobito tijekom prva 3 prolaska vozila te dubina kolotraga jednaka klirensu forvadera nije dostignuta.

U slu~aju prolaska vozila bez polugusjenica na vla`nom tlu (KW80) po~etna je gusto}a tla bila 1,06 g/cm3, dok je gusto}a nakon 4 prolaska vozila porasla do 1,33 g/cm3. Zatim je gusto}a tla bila ne{to manja od 5. do 7. prolaska vozila (1,29 g/cm3) te je njezina vrijednost ujedna~ena i opet smanjena od 8. do 10. prolaska vozila na 1,24 g/cm3.

Dubina se kolotraga naglo pove}avala do 0,40 m osobito tijekom prvih 7 prolazaka vozila, dok dubina kolotraga jednaka klirensu forvadera nije dostignuta.

U slu~aju prolaska vozila s polugusjenicama na vla`nom tlu (KT80) po~etna je gusto}a tla bila 1,05 g/cm3, dok je gusto}a nakon 6. prolaska vozila porasla do 1,33 g/cm3. Zatim je gusto}a tla bila ne{to manja pri 7. do 10. prolaska vozila te se ujedna~ila na vrijednosti od 1,30 g/cm3. Dubina se kolotraga ravnomjerno pove}avala do 0,22 m te dubina kolotraga jednaka klirensu forvadera nije dostignuta.

Istra`ivanje je u oblasti Tver pokazalo da je prosje~na koli~ina vode u tlu iznosila 88 % te da je gusto}a polagane granjevine bila 15 kg/m2 (sl. 3). Gusto}a je tla prije i poslije prolaska vozila prikazana u tablici 3 (TW88 i TT88) od po~etne 1,06 g/cm3.

U slu~aju vozila bez polugusjenica na kota~ima (TW88) gusto}a je tla nakon 5 prolazaka vozila neznatno porasla do 1,10 g/cm3, dok je od 6. do 10. prolaska vrijednost gusto}e tla ujedna~ena na 1,11 g/cm3. Pojavnost kolotraga nije zabilje`ena jer je njihova dubina bila manja od 0,05 m.

U slu~aju vozila s polugusjenicama na kota~ima (TT88) gusto}a je tla nakon 1. prolaska vozila neznatno porasla do 1,08 g/cm3, zatim je vrijednost gusto}e tla porasla od 1,10 do 1,11 g/cm3. Pojavnost kolotraga nije zabilje`ena jer je njihova dubina bila manja od 0,05 m.

44

Croat. j. for. eng. 31(2010)1

Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil ... (35–45)

Yuri Gerasimov and Vasily Katarov

Uz pomo} kubnoga regresijskoga modela dobiveni su koeficijenti determinacije R2 od 0,99 za dubinu kolotraga i 0,80–0,99 za gusto}u tla. Koeficijenti u ovisnosti o uvjetima na terenu (sadr`aj vlage u tlu, kota~i bez polugusjenica ili s njima, granjevina na tlu) prikazani su u tablici 4. Slika 3 prikazuje odnos izme|u privu~enoga drvnoga obujma i dubine kolotraga, a slika 4 prikazuje odnos izme|u privu~enoga drvnoga obujma i gusto}e tla.

Vrsta je tla odre|ena prema ruskom standardu klasifikacije tla koji se temelji na indeksu plasti~nosti i relativnim odnosima frakcija u tlu, {to u krajnosti odre|uje teksturu tla. Naziv razreda tla prilago|en je sustavu USDA (United States Department of Agriculture). Rezultati su klasifikacije tla prikazani u tablici 5.

Rezultati promjene gusto}e tla (zbijanje tla) pokazali su da je sortimentna metoda pridobivanja drva sustavom harvester – forvarder okoli{no prihvatljiva za pjeskovitu ilova~u (gusto}a tla 1,4 g/cm3) unutar granica oblikovanoga pokusa. Me|utim, gusto}a se tla pove}ala na svim plohama istra`ivanja na dubini tla od 0 do 5 cm.

Pove}anje je gusto}e tla ovisilo o broju prolazaka vozila, prisutnosti zastora granjevine na tlu i sadr`aju vlage u tlu. Pri kori{tenju polugusjenica na forvarderu zbijanje je vla`noga i mokroga tla bilo nepravilno. S pove}anjem broja prolazaka vozila zona se zbijenoga tla produbljivala, dok se postavljanjem granjevine na tlu ne prelaze granice postavljenoga pokusa.

Postaviv{i okoli{no prihvatljivu granicu dubine kolotraga od 0,15 m, uporaba forvardera s polugusjenicama na kota~ima na tlima pove}ane vla`nosti (smanjene nosivosti tla) ekolo{ki je neodr`iva. [tovi{e, dubina je kolotraga dosegla visinu klirensa vozila (0,67 m) na mokrom tlu. Pri kori{tenju polugusjenica dubina je kolotraga na mokrom tlu, tako|er, bila ve}a od 0,15 m te je samim time i ekolo{ki nepodobna, ali ipak nije prema{ila visinu klirensa vozila. Polaganjem granjevine na tlo kolotrag nije zabilje`en.

Svi strojni sustavi pridobivanja drva u Rusiji uzrokuju razli~ite vrste negativnih utjecaja na okoli{. Kada se primjenjuju na pjeskovitim ili ilovasto-pjeskovitim tlima, svi su sustavi pridobivanja drva pokazali gotovo isti utjecaj na tlo. Me|utim, udio pjeskovitih tala u ruskim {umama nije zna~ajan. Na glinovitim tlima deblovna i stablovna metoda, za razliku od sortimentne metode pridobivanja drva, uzrokuju zna~ajno ve}a zbijanja tla. Preko 50 % sje~ina u Rusiji se nalazi na mokrim i mekim tlima. Stoga se primjena sortimentne metode mora pobolj{ati kako bi se smanjila dubina kolotraga na tlu te se, ovisno o terenskim uvjetima, treba odrediti kori{tenje ili nekori{tenje polugusjenica na kota~ima vozila (smanjivanje dodirnih tlakova) te debljina polagane granjevine na tlo, a sve radi za{tite tla od negativnoga utjecaja vozila pri privla~enju drva.

Klju~ne rije~i: sortimentna metoda, forvarder, dubina kolotraga, prirodna gusto}a tla, zastor grana, polugusjenica, Rusija

Authors' address – Adresa autorâ: Yuri Gerasimov, PhD. e-mail: yuri.gerasimov@metla.fi Finnish Forest Research Institute Joensuu Research Centre Yliopistokatu 6 Box 68 FIN–80101 Joensuu FINLAND

Received (Primljeno): March 5, 2010 Accepted (Prihva}eno): June 2, 2010 Croat. j. for. eng. 31(2010)1

Vasily Katarov, PhD. e-mail: vkatarov@psu.karelia.ru Petrozavodsk State University Forest Engineering Faculty A. Nevsky av., 58 185030, Petrozavodsk Republic of Karelia RUSSIA

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Original scientific paper – Izvorni znanstveni rad

Assessing Site Disturbance Using Two Ground Survey Methods in a Mountain Forest Akbar Najafi, Ahmad Solgi Abstract – Nacrtak Assessment of disturbance can provide forest managers with information to make appropriate decisions on site rehabilitation and monitoring. This paper evaluates the accuracy of successive estimates of site disturbance using two ground survey methods. The results from the point transect and grid point transect and grid point intercept methods were compared with the results from an intensive 1x1 m grid survey over a 4 ha study area. The point transect method, using a transect spacing of 30 m, provided the most accurate and consistent estimate of disturbance in the study area. Following the harvest, approximately half of all treated area was disturbed to varying levels. Intact forest floor (undisturbed) and light slash were the dominant surface conditions, covering an average of 70% of harvested area. The results indicate that shallow disturbances (litter left in place or removed) were more frequent than deep disturbances (topsoil removed, subsoil exposed, or rut exposed).

Key words: site disturbance, timber harvesting, survey methods, point transect, grid point intercept

1. Introduction – Uvod In forestry operations, the use of ground-based heavy machinery for harvesting is common practice around the world. Forests are known to be the ecosystems that best protect soils and watercourses (Horswell and Quinn 2003). In forest harvesting, there is an ongoing trend to increase almost constantly the size, power and load of logging machines, with weights that generally amount up to 12–16 tones in unloaded state (Ampoorter et al. 2007). This may cause soil degradation in forest ecosystems as the passes of harvesting machines modify important soil structural characteristics (Greacen and Sands 1980, Corns 1988, Jurgensen et al. 1997, Kozlowski 1999, Grigal 2000, Startsev and McNabb 2000, Makineci et al. 2007). Nevertheless, in commercially managed forests where stands are clear-cut and heavy machinery is used for harvesting and site preparation, the maintenance of forest soil sustainability is greatly questioned because plant cover is disturbed and the risk of erosion intensifies (Aust et al. 1995c, Aust et al. 1997b, Hartanto et al. 2003). Site disturbance may result in degradation of soil propCroat. j. for. eng. 31(2010)1

erties (increase soil compaction and decrease soil macroporosity, infiltration), and may cause a decline in site productivity (McMahon 1995). The most significant changes have been shown to occur in soil surface layers (Rab 2004, Pennington and Laffan 2004, Yavuzcan et al. 2005); this can restrict the movement of air and water into soil layers (Rab 1994). Soil disturbance is defined as an alteration in the properties of a soil (dry bulk density, porosity, infiltration) (Quesnel and Curran 2000) and can be used as an index of the environmental impacts of logging (Miller and Sirois 1986, Rab 1999a).

It is important to develop a quick and easy procedure to measure the disturbance of the soil caused by forest practices during harvesting and site preparation in order to asses the effects of the use of heavy machinery and to evaluate forest practices. Assessment of disturbance can provide forest managers with information to make appropriate decisions on site rehabilitation and monitoring. In addition, disturbance assessment may also be required by regulatory bodies to assess compliance (McMahon 1995).

However, the assessment recording of a whole area is a complex and time-consuming procedure. It

47

Akbar Najafi and Ahmad Solgi

Assessing Site Disturbance Using Two Ground Survey Methods ... (47–55)

is also evident that there are major problems in having the surveys carried out in a reliable and consistent fashion.

This study was conducted to evaluate the relative accuracy and consistency of two ground survey methods compared to the intensive 1 by 1 m grid survey method and provides an overview of several ground survey methods in a mountainous forest, and also determines the level of impact by visual classification of soil disturbance in comparison with McMahon (1995).

2. Materials and methods – Materijal i metode 2.1 The study site – Mjesto istra`ivanja The study area – Tarbiat Modares University Forestry Experiment Station, located in a temperate forest in North of Iran, between 36° 31' 56" N and 36° 32' 11" N latitudes and 51° 47' 49" E and 51° 47' 56" longitudes is dominantly covered with Fagus orientalis and Carpinus betulus stands. Canopy cover has been estimated as 80%, average diameter: 29.72 cm, average height: 22.94 m, maximum extraction distance: 400 m and stand density: 170 trees/ha. Records show that 1500 m3 of timber was skidded by Timberjack 450C in May 2007 and immediately thereafter the current study was conducted.

2.2 Ground survey methods – Terenske metode opa`anja Three ground survey methods have been used by researchers to assess site disturbance (McMahon 1995): Þ Point transect (PT) method In this method, disturbance is classified at predetermined points along the survey transect. Intersects are laid generally parallel to the site contours or perpendicular to the contours. Bloomberg et al. (1980) (cited in McMahon 1995) developed a random method of starting point location, which permitted a more statistically valid assessment of variation and sampling intensity. To locate sampling points, a rod is dropped on to the ground surface using the specific chain mark as guide. The coverage (%) of each disturbance class is determined from the number of points in each class and the total number of points sampled. Þ Line transect (LT) method Similarly as with the PT method, disturbance along surveyed transects is classified. As disturbances are encountered along the line, their beginning and end points are recorded as shown in Table 1. The lengths of each of the disturbance classes are summed to determine the relative coverage (%) of the net forested area. Transects are evenly located over a

48

site, parallel to the site contours or a combination of two orientations perpendicular to each other. In a variation on these, Turcotte et al. (1991) used randomly oriented transects to define the disturbance within 10x15 m plots. The minimum length that was recorded (0.1 m) was less than that of the minimum width of disturbance (0.5 m). This ensured that all disturbance features could be recognized. Þ Grid point intercept (GPI) method In this system, the sampling points are determined based on layout of a randomly systematic square grid. The dimensions of the grid are determined by the size of the area being sampled and an estimated sample size (Rab 1999b).The first transect is orientated randomly, and subsequent transects are orientated at 90°, 180° and 270° from the original.

The study area and the skidding directions are shown schematically in Fig. 1. Disturbance was intensively assessed over the area using a 1x1 m spacing between observation points (Fig. 2a). To satisfy the degree of soil disturbance in harvest coupes, various soil surface disturbance categories have been used (e.g. Bukhiem et al., 1975, Murphy 1982, McMahon 1995, Rab 1999a). The classification scheme used for this study was adapted from that of McMahon (1995). Field observations of the soil were categorized on the basis of visible evidence of disturbance (Table 1). At each point, the predominant disturbance class within a 0.3 m radius was classified according to the scheme shown in Table 1.

The disturbance was then assessed using the PT and GPI methods. The LT method was excluded from the method evaluation as it was considered that identification of boundaries among disturbance classes could be too subjective, introducing excessive variation into the assessment results (McMahon 1995).

Fig. 1 Study area layout Slika 1. Shema mjesta istra`ivanja Croat. j. for. eng. 31(2010)1

Assessing Site Disturbance Using Two Ground Survey Methods ... (47–55)

For the PT method, transect spacing of 30 m (PT30), 50 m (PT50) and 80 m (PT80) were used. Transects were orientated perpendicular to the skidding direction (Fig. 2b).

The first transect was located at a randomly assigned distance from the landing, not exceeding the spacing between subsequent transects. For each transect spacing, the method was repeated three times, each with differently located transects.

In the GPI method, 12 grid points were located within the study area at 60x60 m spacing. The distur-

Akbar Najafi and Ahmad Solgi

bance was classified at 1-m intervals along four 30-m-long transects originating from the grid point.

The orientation for the first transect was random, with the second being 180o from the first. The third and fourth transects were orientated at 90o degrees to the first two (Fig. 2c). Where transect crossed outside of the study area, the grid point was adjusted for the affected orientation. The disturbance at the grid point was excluded from the data set (McMahon 1995).

The GPI method was applied three times using different grid points and transects orientations each time.

Fig. 2 Illustration of the three survey methods used in the study Slika 2. Prikaz triju metoda opa`anja primijenjenih u istra`ivanju Table 1 Visual disturbance classification system (McMahon 1995) Tablica 1. Vizualni sustav razvrstavanja o{te}enja (McMahon 1995) Soil disturbance type Vrsta o{te}enja tla

Description Opis

No evidence of machine or log passage, litter and understorey intact Bez traga prolaska stroja ili trupca, listinac i biljni pokrov nedirnuti Litter still in place, evidence of minor disruption – Listinac nepomaknut, uo~ljiv manji poreme}aj Litter removed, topsoil exposed – Listinac uklonjen, tlo vidljivo Shallow disturbance – Povr{inska o{te}enja Litter and topsoil mixed – Listinac i tlo pomije{ani >5 cm topsoil on litter – > 5 cm tla na listincu Topsoil removed – Premje{tanje tla Erosion feature – Erozija tla Topsoil puddled – @itko tlo 5–15 cm Deep disturbance – Velika o{te}enja 16–30 cm Rut depth – Dubina kolotraga >30 cm Unconsolidated subsoil or base rock deposit – Nekonsolidarano tlo ili mati~ni supstrat izlo`en 10–30 cm Slash/understorey residue – Drvni ostaci, granjevina >30 cm Non-soil (stumps, rocks) – Panjevi, stijenje Compacted soil – Zbijeno tlo Evidence of tire, track and/or log passage – O~itost prolaska gume, gusjenice i/ili trupca Undisturbed soil – Neo{te}eno tlo

Croat. j. for. eng. 31(2010)1

Code Oznaka 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

49

Akbar Najafi and Ahmad Solgi

Assessing Site Disturbance Using Two Ground Survey Methods ... (47–55)

Table 2 Soil disturbance assessment results Tablica 2. Rezultati procjene o{te}enja tla Survey method Metoda opa`anja

Number of observation Broj opa`anja

1x1 m GPI PT30 PT50 PT80

40,000 1440 1400 800 600

Soil disturbance – O{te}enje tla, % Undisturbed and shallow disturbances Deep disturbances Neo{te}eno tlo i povr{inska o{te}enja Velika o{te}enja % 89.09 1.22 90.42 0.78 88.68 1.22 89.13 1.16 89.78 1.09

2.3 Data analysis – Obrada podataka For the data sets collected during the 1x1 m PT and GPI surveys, frequency distributions were produced including all 15 disturbance classes (Table 1), as well as the occurrence of compaction. The results for 15 individual classes were combined to represent three types of disturbance: (1) undisturbed and shallow disturbance, (2) deep disturbance, and (3) compaction (McMahon 1995).

The accuracy of the method was defined as »the ability of a measurement to match the actual value of the quantity being measured«. For example, if the outside temperature is 34.0 F and a temperature sensor reads 34.0 F, then the sensor is accurate. The precision was defined as »(1) the ability of a measurement to be consistently reproduced« and »(2) the number of significant digits to which a value has been reliably measured«. If in several tests the temperature sensor matches the actual temperature while the actual temperature is held constant, then the temperature sensor is precise. By the second definition, the number 3.1415 is more precise than the number 3.14.

The accuracy of the PT and GPI methods was assessed by ANOVA, and mean disturbance estimates were compared to intensive 1x1 m grid survey using a Student t-test procedure (McMahon 1995). Method consistency was assessed from the magnitude of

Compacted soil Zbijeno tlo 10.91 9.58 11.32 10.87 10.22

95% confidence, which reflected the range of survey results produced when the method was repeated.

3. Results – Rezultati The results of the 1x1 m grid survey were assumed to represent the absolute disturbance within the study area, and thus were considered the standard by which the other methods would be assessed. Using this method, a total of 40,000 observations were made in the study area compared to 1440, 1400, 800, 600 observations for the GPI, PT30, PT50 and PT80 surveys (Table 2). The potential for sampling error within this absolute measure was recognized.

The estimate percentages for slash cover and non-soil area or points have been omitted. Percentages of undisturbed, shallow disturbance, deep disturbance (presented), slash and non-soil (not presented) add up to 100. All results are expressed as a percentage of the total number of observations made for each individual assessment.

Results from each of the methods are shown graphically in Fig. 3 and summarized in Table 2.

Estimate variations in PT and GPI methods are evident in Fig. 3. Comparing the mean estimates with those of 1x1 m survey, it appeared that the PT30

Table 3 Consistency of survey methods Tablica 3. Pouzdanost metoda opa`anja Survey method Metoda opa`anja GPI PT30 PT50 PT80

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Undisturbed and shallow disturbances Neo{te}eno tlo i povr{inska o{te}enja 98.6 99.6 94.4 95.4

Consistency, % – Pouzdanost, % Deep disturbances Velika o{te}enja 33.8 80.1 72.8 73.2

Compacted soil Zbijeno tlo 86.5 97.0 54.4 59.6

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method consistently provided the most accurate estimates of disturbance.

The consistency of the PT and GPI methods was indicated with the magnitude of 95% confidence intervals attached to the respective mean estimates shown in Fig. 3. For the three types of disturbance, the most consistent method was the PT30.

For three disturbance types, the level of consistency of PT methods decreased as the transect spacing increased from 30 m to 50 m (Table 3).

Results show that most observations (70%) were slash cover (9%) and undisturbed soils (61%). Disturbed soils accounted for nearly 30% of observations with the most comprising shallow (20%) and compacted (8.9%) disturbed classes. Deep disturbed soils accounted for only just over 1.1% of observations. Rutting affected 81% of the deep disturbance classes. Slash residual classes were distributed as 91% Class I (10â&#x20AC;&#x201C;30 cm), 9% Class II (>30 cm).

4. Discussion â&#x20AC;&#x201C; Diskusija

Fig. 3 Selected disturbance results using the 1x1 m survey, mean results and 95% confidence intervals for the PT and GPI methods Slika 3. Rezultati opa`enih o{te}ivanja primjenom 1x1 m metodom opa`anja i srednje vrijednosti rezultata s 95 % intervalom pouzdanosti primjenom metode pravca to~aka i sjeci{ta mre`e to~aka Croat. j. for. eng. 31(2010)1

The results showed that accuracy did not always reflect sample sizes. Although there were no significant differences among the mean estimates provided by the three transect spacing for the PT method, there was variation among them (Table 2). The accuracy was not decreased with increasing the transect spacing from 30 m to 80 m and decreasing the sample size. The large sample size of the PT30 method did appear to provide the most accurate estimate relative to other PT methods.

The mean estimates of both PT30 and GPI methods were based on similar sample sizes (1400 and 1440, respectively). However, the GPI method was less accurate than the PT method (Table 2).

The method consistency was not affected by sample size. From three disturbance types, PT30 provided a more consistent estimate than PT50 and PT80 methods. Similar to accuracy, the PT30 method provided more consistent estimates than the GPI, which had a similar sample size.

The differences in the accuracy and consistency of PT and GPI methods could not be explained by sample size. It is possible that the differences in sampling strategies may also have contributed to method performances (McMahon 1995). Both PT and GPI methods involved contrasting approaches to the location of the observation or sampling points but a systematic approach was used for the PT method, based on transects orientated perpendicular to the dominant extraction direction. In contrast, the GPI method involved the random location of grid point pattern and random orientation of transects. The

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Fig. 4 Examples of causes in variation in estimates between three successive applications of GPI and PT methods Slika 4. Primjer razlike u procjeni izme|u triju uzastopnih primjena metode pravca to~aka i sjeci{ta mre`e to~aka random approach employed by GPI method is likely to result in less consistent estimates of disturbance types which were systematically orientated, parallel to extraction direction (Fig. 4). At bigger transect spacing, disturbance features may be missed in the systematic approach of the PT method relative to the GPI method. In the three successive surveys shown in Fig. 4, it could be expected that the consistency of deep disturbance estimates would be lower for the GPI method. This was the case of the results of this study shown in Fig. 3. This study has highlighted that there are no considerable differences among three methods from consistency and accuracy point of view in a mountainous forest compared to flat area. Disturbance assessment only provides an estimate of actual disturbance levels.

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The results show that the PT30 method was the most consistent for the three types of disturbance.

This is similar to the results of McMahon (1995). In comparison with our study McMahon (1995) found 71% undisturbed and shallow disturbance, 4% deep disturbance, and 37% compacted, when rubber-tired skidders were used. Rab (1996b) reported that following logging and slash burning, on average 11% of the coupe area remained undisturbed, 11% litter disturbed, and 78% had mineral soil exposed. The snig tracks, log landings and disturbed general logging area occupied about 19%, 3% and 66% of the coupe area, respectively. Laffan et al. (2001) indicated that after logging by conventional groundbased skidding from steep slopes, most observations (>70%) were slash cover (47%) and undisturbed soils Croat. j. for. eng. 31(2010)1

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(25%). Disturbed soils accounted for nearly 30% of observations mostly comprising slightly (17%) and moderately (10%) disturbed classes. Severely disturbed (subsoil exposed) soils accounted for only just over 1% nearly all attributable to tree uprooting during logging operations. Heninger et al. (2002) found that soils with a thin topsoil (A and A–B horizons), therefore, are more likely to be classified as severely disturbed than soils with a thick topsoil.

Gondard et al. (2003) found 52% undisturbed and shallow disturbance, 3% deep disturbance, and 37% slash residue, when skidder and terraces were used, and also found 27% undisturbed and shallow disturbance, 0% deep disturbance, and 58% slash residue, when forwarder and terraces were used. Eisenbies et al. (2005) reported that rutting and churning affected 72% of heavy disturbance category. Helvey et al.

(1985) compared five different log retrieval systems (after hand felling) with respect to soil disturbance and erosion: tractor skidding over bare ground (<30% slope), tractor skidding over snow (<40% slope), cable skidding over bare ground, skyline (Wyssen skycrane), and helicopter. They found that tractor skidding over bare ground caused the greatest percentage of area with severe soil disturbance (36%), followed by cable skidding (32%), tractor skidding over snow (9.9%), skyline (2.8%), and helicopter (0.7%).

These reveal that the logging tractor used for skidding is a very important factor, but that the presence of shallow or deep disturbances, and their intensity, also depends on environmental characteristics. McIver and Starr (2001) reported that the type of logging system and the time used for logging relative to soil moisture are both important in determining soil disturbance and sediment transport.

Ground-based systems have a broad range of machinery configurations. Rubber-tired skidders are capable of producing more severe damage than tracked machines due to their ability to continue skidding under more severe terrain. Steel-tracked machinery is also generally considered to have a lower impact on soil than rubber-tired machinery due to lower static ground pressures (Horn et al. 2004).

Murphy (1982) has studied the effect of various types of machinery on severity of soil disturbance. He found that a Clark 66 RTS with its high ground pressure and fast speeds caused more severe soil disturbance than an FMC 100 STS. He also found that the Timbermaster TM70 (RTS) caused less severe disturbance than the Bombardier Muskeg (STS), although the Timbermaster exerted slightly higher ground pressures than the Bombardier Muskeg. This was probably because the Timbermaster had articulated steering while the Bombardier had controlled differential steering (Murphy 1982).

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5. Conclusions – Zaklju~ci The two methods were applied to a 4 ha harvest area, which was harvested recently and logs were removed by a crawler tractor. An intensive 1x1 m grid survey was made over the study area and a field evaluation of two methods of site disturbance assessment was conducted to determine the accuracy and consistency of two ground survey methods, and then the accuracy of the two methods was assessed by comparing mean disturbance estimates with the results of the survey. The two methods were the point transect method, using three different transect spacing, and the grid point intercept method. Method consistency was determined by independently applying the assessment methods three times to the same area. We found that the most accurate estimate of disturbance was provided by the point transect method, with 30 m spacing transects. In contrast, the grid point intercept method provided the least accurate estimates of the disturbance. The point transect method, with 30 m spacing transects, appeared to be more consistent than the other methods.

Feature studies must continue to improve the understanding of the relationship between visual evidence of damage and actual impacts, particularly in relation to compaction related to ecosystem regeneration, soil recovery and ecosystem health and vitality. The present system of defining soil damage on the basis of soil disturbance is based on a well recognized process of visual features. However, it does not incorporate any direct measure or description of compaction, one of the most significant aspects of soil damage. This aspect must presently be inferred on the basis of evidence of traffic (i.e. snig tracks).

Acknowledgements – Zahvala The authors gratefully acknowledge Hormoz Sohrabi for statistic analysis.

6. References – Literatura Ampoorter, E., Goris, R., Cornelis, W. M., Verheyen, K., 2007: Impact of mechanized logging on compaction status of sandy forest soils. Forest Ecology and Management 241(1–3): 162–174.

Aust, W. M., Schoenholtz, S. H., Zaebst, T. W., Szabo, B. A., 1997: Recovery status of a tupelo-cypress wetland seven years after disturbance: silvicultural implications. Forest Ecology and Management 90(2–3): 161–169.

Aust, W. M.., Tippett, M. D., Burger, J. A., McKee, J. R., 1995: Compaction and rutting during harvesting affect better drained soils more than poorly drained soils on wet pine flats. Southern Journal of Applied Forestry 19(2): 72–77.

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Corns, I. G. W., 1988: Compaction by forestry equipment and effects on coniferous seedling growth on four soils in the Alberta foothills. Canadian Journal of Forest Research 18: 75–84.

McMahon, S., 1995: Accuracy of two ground survey methods for assessing site disturbance. Forest Engineering. Logging Industry Research Organization Rotirua, New Zeland. Journal of Forest Engineering 27–33.

Eisenbies, M. H., Burger, J. A., Aust, W. M., Patterson, S. C., 2005: Soil physical disturbance and logging residue effects on changes in soil productivity in five-year-old pine plantations. Soil Science Society of America Journal 69: 1833–1843.

Miller, J. H., Sirois, D. L., 1986: Soil disturbance by skyline vs. skidding in a loamy hill forest, Soil Science Society of America Journal 50: 1579–1583.

Greacen, E. L., Sands, R., 1980: A review of compaction of forest soils. Australian Journal of Soil Research 18(2): 163–189.

Pennington, P., Laffan, M., 2004: Evaluation of the use of pre and post harvest bulk density measurement in wet Eucalyptus oblique forest in southern Tasmania. Ecological Indicators 4: 39–54.

Grigal, D. F., 2000: Effects of extensive forest management on soil productivity. Forest Ecology and Management 138 (1–3): 167–185.

Quesnel, H. J., Curran, M. P., 2000: Shelterwood harvesting in root-disease infected stands-post-harvest soil disturbance and compaction. Forest Ecology and Management 133(1–2): 89–113.

Hartanto, H., Prabhu, R., Widayat, A. S. E., Asdak, C., 2003: Factors affecting runoff and soil erosion: plot-level soil loss monitoring for assessing sustainability of forest management. Forest Ecology and Management 180(1–3): 361–374.

Rab, M. A., 1994: Changes in physical properties of a soil associated with logging of Eucalyptus regnans forest in south-eastern Australia, Forest Ecology and Management 70(1–3): 215–229.

Horswell, M., Quinn, N., 2003: Minimising sediment delivery to rivers: a spatial modelling approach developed for commercial forestry, Diffuse pollution Conference.

Dublin 5A: 1–6.

Jurgensen, M. F., Harvey, A. E., Graham, R. T., Page-Dumroese, D. S., Tonn, J. R., Larsen, M. J., Jain, T. B., 1997: Impacts of timber harvesting on soil organic matter, nitrogen, productivity, and health of inland northwest forests. Journal Forest Science 43(2): 234–251.

Rab, M. A., 1999a: Measures and operating standards for assessing Montreal process soil sustainability indicators with reference to Victorian Central Highlands forest. Forest Ecology and Management 117(1–3): 53–73.

Rab, M. A., 1996b: Soil physical and hydrological properties following logging and slash burning in the Eucalyptus regnans forest of southeastern Australia. Forest Ecology and Management 84(1–3): 159–176.

Kozlowski, T. T., 1999: Soil compaction and growth of woody plants. Scandinavian Journal of Forest Researc 14(6): 596–619.

Rab, M. A., 2004: Recovery of soil physical properties from compaction and soil profile disturbance caused by logging of native forest in Victorian Central Highlands. Forest Ecology and Management 191(1–3): 329–340.

Laffan, M., Jordan, G., Duhig, N., 2001: Impacts on soils from cable-logging steep slopes in northeastern Tasmania, Australia. Forest Ecology and Management 144(1–3): 91–99.

Startsev, A. D., McNabb, D. H.. 2000: Effects of skidding on forest soil infiltration in west-central Alberta. Canadian Journal of Soil Science 80: 617–624.

Makineci, E., Demir, M., Yilmaz, E., 2007: Long-term harvesting effects on skid road in a fir (Abies bornmulleriana Mattf.) plantation forest. Building Environment 42(3): 1538–1543.

Yavuzcan, H. G., Matthies, D., Auernhammer, H., 2005: Vulnerability of Bavarian silty loam soil to compaction under heavy wheel traffic: impacts of tillage method and soil water content. Soil and Tillage Research 84(2): 200–215.

Sa`etak

Procjena o{te}enja stani{ta primjenom dviju terenskih metoda opa`anja u planinskim {umama Smjernice razvoja {umskih vozila, koja se upotrebljavaju pri pridobivanju drva, upu}uju na njihovo pove}anje mase i nosivosti. Izvo|enje radova {umskim vozilima mo`e uzrokovati o{te}enja stani{ta i tla. Pri tome se naj~e{}e zbog prolaska {umskih vozila mijenjaju strukturna svojstva {umskoga tla (pove}ava se prirodna gusto}a i smanjuje poroznost tla), premje{taju slojevi tla te nastaje kolotrag. Ujedno se naru{avaju uvjeti za rast biljaka te se pove}ava opasnost od erozijskih procesa na strmim stani{tima.

Cilj je ovoga rada razvoj brzoga i lakoga postupka za procjenu o{te}enja stani{ta i {umskoga tla koja nastaju pri radovima na pridobivanju drva. U radu je prikazana procjena o{te}enja stani{ta primjenom dviju metoda

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opa`anja, a rezultati su uspore|eni s procjenom o{te}enja provedenom detaljnom metodom opa`anja u mre`i to~aka razmaka 1x1 m. Za ispitivane metode opa`anja o{te}enja stani{ta odre|ena je to~nost i pouzdanost izmjere.

Istra`ivanje je provedeno u planinskim {umama sjevernoga Irana, u odjelu nakon zavr{etka privla~enja drva skiderom Timberjack 450C. Ukupno je privu~eno 1500 m3 drva pri srednjoj udaljenosti privla~enja od 400 m.

Mjesto istra`ivanja s nazna~enim pravcem privla~enja drva prikazano je na slici 1.

Na po~etku su uo~ena i razvrstana sva o{te}enja {umskoga tla u mre`i to~aka razmaka 1 x 1 m. O{te}enja stani{ta i {umskoga tla razvrstana su prema sustavu prikazanom u tablici 1. Postotni je udio pojedine vrste o{te}enja tla odre|en iz broja to~aka (stajali{ta) na kojem je uo~eno o{te}enje u odnosu na ukupan broj to~aka (stajali{ta). U rezultatima je 15 vrsta o{te}enja tla raspodijeljeno u tri grupe: Þ neo{te}eno tlo i povr{inska o{te}enja ⇒ velika o{te}enja i ⇒ zbijeno tlo.

Zatim je procijenjeno o{te}enje primjenom metoda pravca to~aka (PT – point transect) i sjeci{ta mre`e to~aka (GPI – grid point intersect).

Prema metodi pravca to~aka (PT) o{te}enja se uo~avaju i razvrstavaju na odre|enim to~kama/stajali{tima u pravcu. Pravac se postavlja paralelno s granicama odjela i okomito na pravac privla~enja drva. Koriste}i mjerni lanac na odre|enim se udaljenostima po pravcu odre|uju stajali{ta (slika 2b). U istra`ivanju se u primjeni ove metode koristila udaljenost izme|u stajali{ta u pravcu od 30 m, 50 m i 80 m.

Primjenom metode sjeci{ta mre`e to~aka (GPI) na povr{ini su istra`ivanoga odjela odre|ene mre`e to~aka veli~ine 60 x 60 m. Na pravcima duljine 60 m odre|ena su stajali{ta za procjenu o{te}enja u razmaku od 1 m.

Polo`aj je prve mre`e to~aka odre|en nasumi~no, druge pod kutem 180o, a tre}e i ~etvrte mre`e to~aka pod kutem od 90o u odnosu na prve dvije (slika 2c).

To~nost je izmjere odre|ena statisti~kim programom ANOVA, a procjena je srednje o{te}enosti stani{ta uspore|ena s rezultatima opa`anja u mre`i to~aka 1 x 1 m primjenom Student t-testa. Pouzdanost je pojedine metode opa`anja odre|ena njezinim trostrukim ponavljanjem na istra`ivanoj povr{ini.

Rezultati su istra`ivanja prikazani u tablici 2 i na slici 3. Usporedbom rezulata pojednih metoda vidljivo je da primjena metode pravca to~aka s razmakom stajali{ta od 30 m (PT30) daje najto~nije rezultate, odnosno najbli`e vrijednosti u odnosu na rezultate opa`anja s detaljnom izmjerom o{te}enja u razmaku stajali{ta 1x1 m. Isto tako metoda pravca to~aka s razmakom stajali{ta od 30 m ima najve}u pouzdanost izmjere (tablica 3).

Rezultati pokazuju da to~nost metode ne ovisi mnogo o veli~ini uzorka. Pove}anje razmaka izme|u stajali{ta na pravcu je neznatno smanjilo to~nost i pouzdanost. Razlike u opa`anju o{te}enja primjenom ispitivanih metoda ne mogu se obrazlo`iti veli~inom uzorka (slika 4). Metoda je sjeci{ta mre`e to~aka (GPI) zasnovana na slu~ajnom polo`aju to~aka stajali{ta, {to mo`e rezultirati manjom pozdano{}u od metode pravca to~aka (PT) koja je sustavno postavljena s obzirom na pravac privla~enja drva. S druge strane ve}i razmaci izme|u to~ka na pravcu (PT) mogu prouzro~iti propust u uo~avanju o{te}enja u odnosu na metodu sjeci{ta mre`e to~aka (GPI).

Klju~ne rije~i: o{te}enje stani{ta, pridobivanje drva, metode opa`anja, pravac to~aka, sjeci{te mre`e to~aka

Authors' address – Adresa autorâ:

Received (Primljeno): June 14, 2008 Accepted (Prihva}eno): November 17, 2009 Croat. j. for. eng. 31(2010)1

Asst. Prof. Akbar Najafi, PhD. e-mail: a.najafi@moadres.ac.ir Ahmad Solgi, MSc. e-mail: solgi_ahmad231@yahoo.com Tarbiat Modares University Faculty of Natural Resources P.O.Box 46414-356 Noor, Mazandaran Province IRAN

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Original scientific paper – Izvorni znanstveni rad

Analysis of Tree Damage Caused by Excavated Materials at Forest Road Construction in Karst Region Tolga Ozturk, Muhittin Inan, Abdullah E. Akay Abstract – Nacrtak Opening-up of forests enables the application of rational forestry, which means more productivity and suitability for sustainable use. Therefore, forest roads are one of the most important tools needed. This study investigates tree damage caused by excavated materials during forest road construction in a karst region. Bending, crushing and wounding were defined as tree damage because of excavated materials during forest road construction. Besides, forest road construction techniques, and productivity by using hydraulic excavator were investigated in forested lands in Antalya region in Turkey. The number of damaged trees regarding various gradient classes was also determined in the study area. The results indicated that during the forest road construction 12% and 27% of trees were wounded upon 20–45% and 46–90% ground slopes respectively. A maximum length of the fill slope for excavator was found to be 17 m on 80% slope gradient. The cost of excavator was calculated as 17.6 /m. The productivity of the excavator was calculated as 105.8 m3/hr.

Key words: Hydraulic excavator, forest road, road construction, tree damage, excavated materials

1. Introduction – Uvod According to the Turkish General Directorate of Forestry (GDF), the technical and economical management of forests requires 210,000 km of forest roads to be constructed. Up to now, approximately 150,000 km of forest roads have been constructed.

GDF plans to construct 1000 km of new forest roads per year, so they will be on the agenda for a long time to come (Gumuº et. al. 2009). The forest roads are the base infrastructure foundations which provide access to forest lands for extraction, regeneration, protection, and recreation activities (Demir and Hasdemir 2005).

However, designing low-volume forest roads is a complex engineering problem involving economic, environmental, and social requirements. Construction and maintenance costs are the largest components in the total cost of producing the timber for industrial uses (Akay 2006). Besides, road construction activities remove the forest vegetation and disturb soil structure, which may lead to a significant environmental damage in forest ecosystem (Grace 2002).

For example, the sediment yield delivered from forest roads to streams results in dramatic impacts on Croat. j. for. eng. 31(2010)1

water quality and aquatic life (Akay et al. 2008). Besides, planning forest road networks depends on social requirements since they provide access to forest villages, rural settlements, and recreational areas (Acar and Eker 2007). Therefore, forest roads construction activities must be carefully executed by considering economical, environmental, and social requirements (Akay and Sessions 2005).

In locating forest roads, construction methods and equipment selection directly affects the economical, functional, and ecological efficiency of the forest roads. Upon the terrains with gentle to moderate hillside slopes, bulldozers have been still commonly used in right-of-way, cut and fill slope, and subgrade activities. However, in steep and rocky terrain conditions, the efficiency of bulldozers diminishes and excessive environmental damage may occur, since it becomes troublesome to keep the excavated material along the day-light point of fill slopes. In order to reduce the environmental damage on forest ecosystems, especially on steep terrains, hydraulic excavators have replaced bulldozers in forest road construction activities (Stjernback 1982). Besides, the use of excavator improves the quality of forest roads,

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which extends life of the roads, improves the driver’s comfort, and reduces the frequency of maintenance activities. In fact, using excavators can be the only option to perform feasible road construction activities on steep mountainous terrains (FAO 1998).

Excavator has the advantage of performing excavation activities with better control, and it places the material efficiently upon fill slope. In a study conducted by Erdas (1986), it was indicated that excavator should be used in construction activities on steep terrains to reduce environmental impacts. Bayoglu (1986) suggested that bulldozers should be used in the forested areas with less than 40% ground slope, while excavators should be preferred when the slope is greater than 40%. According to Spaeth (1998), a combination of bulldozers and excavators can be used in road construction activities on terrain with slopes greater than 50%.

Winkler (1999) evaluated the productivity of excavators by considering various types of road lengths and terrain conditions. The results indicated that the production rate of excavators was satisfactory in forest road construction. The performance of a skilled excavator operator can play an important role in reducing operation costs. Excavators perform road construction activities in stationary position with limited movements between work sites. Thus, excavators can not move further distances to collect material from outside of the work zone (Stjernback 1982).

The studies indicated that road construction activities using excavator have advantages in the long run due to reduced damage caused to forest ecosystems, biodiversity, and forest soil (Haanshus 1998; Winkler 1999). Heinrich (2001) indicated that excavators were commonly used in environmentally sensitive areas to reduce impact on forest vegetation, provide adequate drainage system, protect stream crossings, and improve the stabilization of cut-andfill slopes. Excavators work with the narrow rightof-way method to reduce disturbance of the forest cover and decrease the risk of erosion in open areas.

Besides, the ground pressure of excavators on forest soil is less than that of bulldozers (Stjernback 1982).

Due to lower ground pressure, excavators can work in wet areas, while bulldozers would most likely stuck in mud.

In order to take advantage of using excavators in forest road construction, the performances of the excavator should be evaluated considering economical and environmental requirements. In this study, forest road construction techniques by using hydraulic excavator were investigated based on a sample road construction activity conducted in forested lands in Antalya region in Turkey.

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2. Materials and Methods – Materijali i metode 2.1. Study Area – Podru~je istra`ivanja The study area is selected from the office zone of Aykiricay Forest Enterprise in Finike Forest Management (Fig. 1).

Fig. 1 The location of the study area in Antalya region Slika 1. Mjesto istra`ivanja In this enterprise, dominant commercial tree species include Pinus brutia, Cedrus libani, Juniperus sp. and Quercus sp. The elevation ranges from 700 m to 900 m with ground slopes of 20% to 100%. The study area consists of Type B forest roads with a density of 14 m/ha. Total length of the sample road examined in this study was about 1640 m with an average road width of 5 m. The study area is located on the Taurus Mountains, which is the largest and most important karst region in Turkey. According to Boydak (2003), this region has one of the most complex karst circulation system and rough terrain characteristics such as sharp peaks, deep valleys, and narrow gorges. Due to immediate penetration of rainfall and snow melt into the rock crack system, surface soil formation very slowly occurs along the cracks and stratification surfaces of the limestone (Boydak 2003).

2.2. The Equipment Specifications Karakteristike opreme Daewoo Solar 220 LC-V type hydraulic excavator and Soosan SB 81 TS type hydraulic hammer were used in forest road construction activity. The undercarriage of the excavator was equipped with fulllength track guards and had a protective plate. The technical specifications of the excavator and hammer are shown in Table 1.

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Table 1 Technical features of the Daewoo Solar 220-LC-V and hydraulic hammer (Anonymous 2007) Tablica 1. Tehni~ke zna~ajke bagera Daewoo Solar 220-LC-V opremljenoga hidrauli~nim ~eki}em Specifications – Karakteristike Values – Vrijednosti Weight – Te`ina 21500 kg Capacity of bucket – Obujam lopate 0.93–1.17 m3 Engine type – Vrsta motora DB58TIS Engine power – Snaga motora 148–1950 PS/rpm Speed – Brzina rada 5 km/hr Max. force – Maksimalna snaga 13100 kgf Max. excavation depth – Maks. dubina kopanja 6630 mm Max. unloading height – Maks. visina utovara 6810 mm Boom turn speed – Maks. brzina zaokreta 10.9 d/min Fuel tank – Spremnik za gorivo 370 liters Hydraulic hammer – Vrsta hidrauli~noga ~eki}a Soosan SB81TS Working weight – Radna te`ina 1721 kg Working pressure – Radni pritisak 160–180 kg/cm2 Number of stroke – Broj udaraca ~eki}a (frekvencija) 400–490 bpm Hammer diameter – Promjer ~eki}a 140 mm Excavator types – Vrsta bagera 18–34 ton

Fig. 2 The decision variables measured from each cross section along the road Slika 2. Mjerenja na svakom profilu ceste

2.3. Methods – Metode

fect of positional values of damaged trees were investigated by means of the data collected.

Area and tree measurements were made to determine and investigate the damage caused by excavated material. Primarily, the cross sections were determined along road route. Some data were thus revealed during forest road construction with hydraulic excavator. These variables include cut-slope height (Ch), cut-slope width (Cw), ditch width (Dw), road width (Rw), fill-slope width (Fw), fill-slope length (Fl), road construction zone width (L), length of the impact zone beyond the fill-slope (P), and ground slope (S) (Fig. 2). The width of excavation and fill-slope length are important for this study. The amount of excavated materials and the slope gradient are also important, because the fill slope length increases with increasing slope gradients, and the damage consequently grows.

The surveying instruments such as clinometers, steel tape, measuring batten, altimeter, and compass were used in the field study. Along the 1640 m of the sample road section, decision variables were collected from 32 cross sections, which were 50 m apart.

The number of damaged trees and undamaged tree were determined between two cross sections as gradient groups (Fig. 3). Observed were also the types of damage such as bending of tree, crushing of tree and wounding of stem. Distribution by damage type, relation to construction techniques and the efCroat. j. for. eng. 31(2010)1

3. Results – Rezultati In the first stage of road construction, 354 m3 of logs were extracted by felling 345 trees along the road construction zone of the sample road. The trees fallen were mostly Pinus brutia and Cedrus libani. The logging residuals were placed on the fill-slope as a barrier that prevents the material from falling down the fill-slope. The results indicated that total exca-

Fig. 3 Determination of cross sections along road route Slika 3. Utvr|ivanje popre~noga presjeka 59

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Table 2 The values of decision variables measured on the cross sections Tablica 2. Vrijednosti mjerenja na svakom profilu ceste Variables – Varijable Ground slope – Nagib terena, % Cut-slope height – Visina pokosa iskopa, m Cut-slope width – [irina pokosa iskopa, m Ditch width – [irina odvodnoga jarka, m Road width – [irina kolnika, m Fill-slope width – [irina nasipa, m Fill-slope length – Duljina pokosa nasipa, m Impact zone length – Pojas utjecaja stroja, m Construction zone width – [irina planuma, m

Symbol Oznaka

Average Prosjek

S Ch Cw Dw Rw Fw Fl P L

59.38 3.46 1.14 0.78 4.10 4.94 3.67 4.29 7.47

vated material along the roadway was 12 480 m3, of which the percentages of soil, loose rock, and rock were 24.88%, 25.19%, and 49.93% respectively. In road construction activities, explosives were not used for crushing rocks. The average operation time of the hydraulic excavator was 8 hours per day. Since it is very hot in Antalya in the summer season, the excavator operated from 7:00 to 11:00 AM in the morning, and from 14:00 to 18:00 PM in the afternoon. The values of the specific variables measured on the cross sections were listed on Table 2.

The average construction zone width was 7.47 m; therefore, sample road section impacted approximately 1.23 ha of the forested area (7.47 m ´ 1640 m) during the road construction activity. The total road construction cost was found to be 28,922 , with the unit cost of 17.6 /m. The production rate of the excavator is generally computed as the length of constructed road per hour. In this study, the average production rate of the excavator was found to be 8.0 m/hr.

The excavator excavated 36 m3 of material per hour and cleared them away from the roadway. The productivity of the excavator was found as 105.8 m3/hr.

This high productivity indicated that hydraulic excavators combined with hydraulic hammers can

Standard Deviation Standardna devijacija 28.39 2.15 0.75 0.08 0.09 2.70 3.47 3.13 2.31

Max. values Mak. vrijednost

Min. values Min. vrijednost

110.0 7.2 2.5 1.0 4.3 10.8 12.0 10.0 14.0

5.0 0.5 0.2 0.7 4.0 1.2 0.2 0.5 5.0

perform excavation operations quickly and effectively in karst regions.

In road construction activity, optimum excavator operating techniques were tried to be implemented to minimize residual stand damage and overall environmental impacts. For example, after rocks were crushed by the hydraulic hammer, they were then carefully placed on the fill slope by using the bucket.

Besides, the cut slope rate of 5:1 was maintained along the roadway to ensure slope-stability in terrains with steep hillside gradients. In fact, the cut slope rate of 5:1 is the most appropriate rate for karst areas, especially for steep terrains.

The percent of damage as wounding, crushing and bending of trees are 75%, 17% and 8% respectively (for 25–45% terrain slope) and 80%, 16% and 4% respectively (for 46–90% terrain slope). The number and rate of the damaged trees in the study areas are shown in Table 3.

In the 46–90% slope areas, the total number of damaged trees on forest roads construction by using excavator is 25. The damage rate of the excavator is 27%. On the terrain less than 45%, the number of total damage is 9. Wounding damage prevails in this area. The percentage of damage as bending, crushing and wounding is shown in Fig. 4.

Table 3 Number and rate of the damaged trees in the study areas Tablica 3. Broj i u~estalost o{te}enja stabala na istra`ivanom podru~ju Average terrain slope, % Prosje~ni nagib terena, %

Number of damaged trees Broj o{te}enih stabala

Number of non damaged trees Broj neo{te}enih stabala

20–45 46–90

12 25

90 68

60

Types of damages – Vrsta o{te}enja Number of total Damage rate, % Wounding trees Bending Crushing U~estalost Stabla s Ukupni broj stabala o{te}enja, % Savijena stabla Otkinuta stabla ozlije|enim deblom 1 2 9 102 12 1 4 20 93 27

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Fig. 4 The rate of damage on trees according to slope gradient Slika 4. U~estalost o{te}enja na stablima s obzirom na nagib terena Bark beetles can occur upon damaged trees during road construction. The species of bark beetle in this region is Orthotomicus tridentatus. These beetles were caused big damage in this forest region. Thus, the direct economic loss was increased due to lesser timber quality. The damage on road construction is shown in Fig. 5.

4. Discussion – Rasprava Previous studies indicated that forested areas under the road construction using bulldozers suffered much more damage than the ones in which hydraulic excavators were used. Besides, the visual quality

of the forest roads constructed by using hydraulic excavators is much better that where bulldozers were used, considering technical and environmental aspects (Bayoglu 1989).

The average construction zone width was found as 7.47 m in this study. A study conducted in Antalya region (Tunay and Melemez 2004) reported that a road construction activity on a terrain with 36–50% ground slope resulted in 9.40 m and 12.18 m wide road construction zones by using excavator and bulldozer respectively. This suggested that the forested area using bulldozers was approximately 29.58% bigger than that using excavators. Tunay and Melemez (2004) also indicated that the bulldozer results in

Fig. 5 Damaged trees Slika 5. O{te}ena stabla Croat. j. for. eng. 31(2010)1

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about 26.16% more affected forest area than does the excavator in road construction activity.

In this study, the total road construction cost was found to be 28,922 , with the unit cost of 17.6 /m.

Besides, the average product rate of the excavator was found to be 8 m/hr. In a study conducted by Winkler (1999) in Himalaya (Bhutan), the unit cost of construction by excavator was 7.58 /m with the production rate of 6.91 m/hr. Acar and Eker (2001) conducted a similar study in Eastern Black Sea Region of Turkey, where 4341 m of forest road was constructed by an excavator on a steep terrain with 70% ground slope. In that study, the unit cost of road construction, and average production rate were 4.74 /m and 8.67 m/hr respectively. Another study conducted by Filipsson and Eriksson (2004) in Sweden indicated that the average productivity of using excavators in road construction was 12.7 metres per hour.

In this study, the unit cost of road construction (17.6 /m) was higher than the unit costs reported by the previous studies. This was because the study area was located on a karst region with rough terrain characteristics and large amount of rocks (6232 m³) to be excavated along the roadway. Besides, ground slope, soil characteristics, and operator factors might affect the cost of road construction. Cut slope rate for karst steep terrains in this study was determined as 5:1. Another study conducted by Kramer (2001) inicated that the cut slope rate of 5:1 is the most apropriate rate for especially steep terrains (Kramer, 2001).

5. Conclusions – Zaklju~ci In this study, the forest road construction techniques by using hydraulic excavator were evaluated by considering economical, technical and environmental requirements. The following suggestions are made in the light of the previous studies and the results derived from the sample road construction activity: Þ The use of excavator in forest road construction activities should be encouraged and even mandatory in mountainous regions with steep terrains. Þ In order to reduce road construction costs and environmental impacts, the excavators should replace bulldozers, especially in Antalya region where explosives are used on karst lands with great threat to forest ecosystems. Þ Economical issues but also environmental requirements. Excavator operators should be well trained to improve the efficiency of construc-

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tion activity, regarding economical and environmental aspects. Þ In the planning phase of the forest roads, the methods and equipment selection should be predetermined not only considering the

6. References – Literatura Acar, H. H., Eker, M., 2001: Excavator using for the forest road construction at step terrain and its case in Turkey.

Proceedings of Third Balkan Scientific Conference, Vol. 5.

Bulgaria: 257–268.

Acar, H. H., Eker, M., 2003: The Use of Excavators in Forest Road Construction and Their Environmental Benefits.

Journal of South-West Anatolia Forest Research Institute, Vol. 5: 98–128.

Akay, A. E., Sessions, J., 2005: Applying the decision support system, TRACER, to forest road design. Western Journal of Applied Forestry 20(3): 184–191.

Akay, A. E., 2006: Minimizing total costs of forest roads with computer-aided design model. Academy Proceedings in Engineering Sciences (SADHANA) 31(5): 621–633.

Akay, A. E., Erdas, O., Reis, M., Yuksel, A., 2008: Estimating sediment yield from a forest road network by using a sediment prediction model and GIS techniques. Building and Environment 43(5): 687–695.

Anonymous, 2007: Daewoo excavator technical catalog. www.dayko.com.tr/urun grup.asp Bayoglu, S., 1986: Development and Mechanization at Forestry. Mechanization and Productivity at Foretsry, 1st National Symposium, MPM Proceeding, No. 339. Ankara, 38–67.

Bayoglu, S., 1989: A Road ConstructionTechnic to Undamaged at Forest and Environment on Steep Terrain. Journal of Forest Engineering 26(12): 6–9.

Boydak, M., 2003: Regeneration of Lebanon cedar (Cedrus libani A. Rich.) on karstic lands in Turkey. Forest Ecology and Management 178(3): 231–243.

Demir, M., Hasdemir, M., 2005: Functional planning criterion of forest road network systems according to recent forestry development and suggestion in Turkey. American Journal of Environmental Sciences 1(1): 22–28.

Erdas, O., 1986: The Rationale Use of Cut and Transport Machines Connected with Project and Construction Technic on Forest Roads. Mechanization and Productivity at Forestry, 1st National Symposium, MPM Proceeding, No. 339. Ankara, 110–128.

FAO, 1998: A manual for the planning, design and construction of forest roads in step terrain. Food and Agriculture Organization of the United Nations. Research Paper, Rome, Italy.

Filipsson, S., Eriksson, L. O., 1989: A Model for predicting productivity in subgrade preparation of forest roads by excavator. Journal of Forest Engineering 1(1): 3–8.

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Grace, J.M., 2002: Control of sediment export from the forest road prism. ASAE Annual Meeting 45(4): 1127–1132.

gon State University, Forest Research Laboratory, Research Contribution 35. USA, 10–11.

Gumus, S., Aricak, B., Enez, K., Acar, H. H., 2009: Analysis of tree damage caused by rockfall at forest road construction works, Croatian Journal of Forest Engineering 30 (2): 151–158.

Spaeth, R., 1998: Environmentally sound forest road construction in northein-westfalen (NRW) Germany. Proceeding of Seminar on Environmentally Sound Forest Roads and Wood Transport. Romania, 109–118.

Haanshus, S., 1998: Environmentally sound construction methods on use of appropriate equipment. Proceeding of Seminar on Environmentally Sound Forest Roads and Wood Transport. Romania, 215–229.

Stjernberg, E. L., 1982: The use of hydraulic backhoes in forest road construction: Centre and Eastern Canada. Feric Publications. No 59, Canada.

Heinrich, R., 2001: The use of excavator in forest road construction in Austria. Proceedings from Third Meeting of Excavators and Backhoe Loaders as Base Machines in Forst Operations, FAIR-CT98-381, SUAS Research Note 11. Sweden, 61–66.

Kramer, B. W., 2001: Forest road contracting, construction and maintenance for small forest woodland owners. Ore-

Tunay, M., Melemez, K. 2004: The assessment of environmentally sensitive forest road construction technique in difficult terrain conditions. I.T.U. Journal of Engineering 3(2–5): 3–10.

Winkler, N., 1999: Environmentally sound forest infrastructure development and harvesting in Bhutan, FAO Forest Harvesting Case Study 12. Rome, 68–70.

Sa`etak

Analiza o{te}enja dube}ih stabala pri izgradnji {umskih cesta u kr{kom podru~ju Turske Prema Op}oj upravi za {umarstvo Turske (OU[) gospodarenje {umama zahtijeva izgradnju dodatnih 210 000 km {umskih cesta. Do sada je izgra|eno otprilike 150 000 km {umskih cesta, a u budu}nosti OU[ planira izgradnju 1000 km {umskih cesta godi{nje. [umske su prometnice osnovni temelji infrastrukture koji omogu}uju pridobivanje drva, obnovu i za{titu {uma te rekreacijske djelatnosti na {umskom zemlji{tu. Me|utim, projektiranje je {umskih cesta u {umama niskoga prihoda slo`en in`enjerski postupak koji uklju~uje ekonomske, ekolo{ke i dru{tvene potrebe i zahtjeve. Ova studija istra`uje o{te}enja stabala pri gradnji {umskih cesta na kr{kom podru~ju.

Savijanje i kidanje stabala te ozlje|ivanje debla smatra se o{te}enjem odnosno {tetom nastalom prilikom izgradnje {umskih cesta. Osim toga, istra`ivan je i na~in gradnje te produktivnost hidrauli~nih bagera za izgradnju {umskih cesta u {umariji Aykiricay, okrug Finike, regija Antalya u Turskoj. Glavne i ekonomski najisplativije vrste drve}a na ovom su podru~ju Pinus brutia, Cedrus libani, Juniperus sp. i Quercus sp. Nadmorska je visina istra`ivanoga podru~ja od 700 do 900 m, dok je nagib terena od 20 do 100 %.

Istra`ivano je podru~je otvoreno {umskim cestama tipa B s gusto}om prometnica od 14 m/ha. Ukupna je duljina istra`ivane trase ceste bila 1640 m, a {irina je planuma bila 5 m te su svakih 50 m prikupljani podaci s 32 popre~na profila. Istra`ivano podru~je pripada planinskomu masivu Taurus koji je ujedno i najve}e i najva`nije kr{ko podru~je Turske. Na izgradnji je ceste radio hidrauli~ni bager Daewoo Solar 220 LC-V s hidrauli~nim ~eki}em Soosan SB 81 TS. Pobrojana su o{te}ena i neo{te}ena stabla izme|u svaka dva susjedna popre~na profila te su odre|ivani tipovi o{te}enja stabala kao {to su savijanje i kidanje stabala te ozlje|ivanje debla prilikom izgradnje {umske ceste.

Koli~ina je iskopa du` prometnice bila oko 12 480 m3 materijala s 24,88 % udjela zemlje; 25,19 % udjela mje{avine zemlje i kamenja te 49,93 % udjela stijene. Pri izgradnji prometnice nije kori{ten eksploziv, a prosje~no je vrijeme rada hidrauli~noga bagera bilo 8 sati na dan, prosje~na je {irina pojasa izgradnje bila 7,47 m, {to zna~i da je povr{ina ceste u izgradnji zauzela oko 1,23 ha {umske povr{ine. Ukupni su tro{kovi izgradnje iznosili 28 922 , s jedini~nom cijenom od 17,6 /m. Bagerom je po satu rada prosje~no iskopano i o~i{}eno 36 m3 materijala s trase ceste, odnosno brzina je rada bagera iznosila 8 m/h. Produktivnost je bagera bila 105,8 m3/h. Na terenu nagiba od 25 % do 45 % postotni je udio o{te}enja na stablima iznosio: savijanje stabala 8 %, kidanje stabala 17 % i ozlje|ivanje debla 75 %. Na terenu nagiba 46 – 90 % postotni je udio o{te}enja na stablima iznosio: savijanje

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stabala 4 %, kidanje stabala 16 % i ozlje|ivanje debla 80 %. Na terenu nagiba 46 – 90 % ukupno je o{te}eno 25 stabala, udio je o{te}enja radom bagera 27 %, dok je na terenu nagiba do 45 % ukupno o{te}eno 9 stabala s ve}inskim o{te}enjen na deblu.

Zbog nastalih o{te}enja na stablima prilikom izgradnje {umskih prometnica stabla mogu napasti potkornjaci te bi se tako na istra`ivanom podru~ju mogla pojaviti vrsta Orthotomicus tridentatus. Ona u ovom podru~ju izaziva velike {tete pa stoga pri izgradnji {umskih prometnica treba biti posebno oprezan.

Authors' address – Adresa autorâ: Asst. Prof. Tolga Ozturk, PhD. e-mail: tozturk@istanbul.edu.tr Istanbul University Faculty of Forestry, Department of Forest Construction and Transportation 34473, Bahcekoy Istanbul TURKEY Dr. Muhittin Inan, PhD. e-mail: inan@istanbul.edu.tr Istanbul University Faculty of Forestry Department of Surveying and Cadastre 34473, Bahcekoy Istanbul TURKEY

Received (Primljeno): November 26, 2008 Accepted (Prihva}eno): June 7, 2010

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Asst. Prof. Abdullah E. Akay, PhD. e-mail: akay@ksu.edu.tr Kahramanmaras Sutcu Imam University Faculty of Forestry Department of Forest Engineering 46060 Kahramanmaraº TURKEY Croat. j. for. eng. 31(2010)1

Preliminary note – Prethodno priop}enje

Working Conditions and Productivity Under Private and Public Logging Companies in Tanzania Dos Santos A. Silayo, Said S. Kiparu, Ernest W. Mauya, Dunstan T. K. Shemwetta Abstract – Nacrtak Industrial timber harvesting in plantation forests in Tanzania was solely performed by public agencies until mid 1980’s. During that period harvesting operations were labour-intensive and semi-mechanized, coupled with low production rates and high production costs.

Following the privatization of forestry industries, logging is currently being carried out by private companies. This study was carried out to assess and compare working conditions, physical workload and productivity in logging operations under private and public logging regimes. Data were collected in Sao Hill Forest plantations from a clear felling operation being carried out in a 26 years old Pinus patula stand. Time study was undertaken for tree cutting, skidding, manual bunching and loading operations. Physical workload data were obtained through heart rate measurement by using portable electronic heart rate monitor.

Working conditions were assessed through ergonomic checklist administered to 45 loggers.

The results indicated that the productivity in tree cutting averaged 4.7m3/h and 3.4m3/h for chainsaw and crosscut operations respectively, while in bunching and loading the respective values of 5.1m3/h and 11.3m3/h made higher production on the private regime as compared to the public. The working conditions were generally poor with low safety, inadequate payment and poor working tools coupled with high labour turnover. The physical workload was 78% and 65% heart rate increase for crosscut saw and chainsaw crews. This is a slight increase compared to the public logging regime estimated at 65% and 57% increase for crosscut saw and chainsaw respectively. However, the increased productivity observed in the private regime was not due to improved working conditions, but rather a result of the workers’ higher engagement and placed effort in performing production tasks. Training of the crews, improvement of payments, supervision and provision of safety gears are recommended for improved production and reduced occupational health hazards.

Keywords: Workers safety, physical workload, costs, timber harvesting, Tanzania.

1. Introduction – Uvod Industrial timber harvesting in plantation forests in Tanzania started in the 1970’s after most plantations attained their rotational age. Harvesting operations were solely performed by public agencies with all the crews or workers being public servant of the government of Tanzania (Ahlback 1986). Most of the logging operations during this period were labour-intensive and semi-mechanized (Dykstra 1983). Tree cutting was done manually using two-man crosscut saw, axes, bow saws and a less labour-intensive chainsaw method. Logs were skidded to the landings by either hand drawn sulkies, farm tractors fitCroat. j. for. eng. 31(2010)1

ted with one or two-drum logging winch(es), crawler tractors, articulated wheeled skidders, or frame-steered forwarders (Nshingo 1988). Log hauling from plantations to mills was done by farm tractors with trailers, 7 to 10 ton flat-bed trucks, or logging trucks with semi or full log trailers. Manual and mechanized loading and unloading was the most common (Migunga 1996). Long distance transport was mainly by either straight trucks or a few tractor-trailer units.

Studies by (Migunga 1982, Ally 1987, Fue and Ole-Meiludie 1989, Mialla 1989; Habyalimana 1990, Malisa 1992, Migunga 1996, Abeli and Shio 1996,

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and Silayo et al. 2007) showed that harvesting production rates had been relatively low with high operating costs. This was due to a number of challenging conditions, which included poor working conditions; high energy demands and relatively low pays which required necessary improvements.

Therefore, since 1985, Tanzania has been undertaking a number of economic and market reforms in order to raise the economic growth and hence improve the performance of different sectors. One of the reforms was privatisation of production sectors, including forestry (Mayawalla 1994). Through privatisation, some of the wood-based industries have been liquidated or sold, and some have entered into joint ventures or leased to private investors (Ngaga et al. 1999). Privatisation of wood industries, which depend largely on logging operations for supply of wood raw material, was expected to bring higher operation efficiency to improve production and lower production costs due to improved supervision and working conditions.

However, studies have shown that even after privatisation of forest industries, logging operations continued to be both labour-intensive and semi-mechanized (Mahenge 2001, Phillip 2001, Ole Meiludie et al. 2002) with slight increase in productivity. Studies show a 28.5% increase in logging productivity in private logging at a 25% decrease in tree cutting costs by using crosscut saw and a 32.6% increase in cutting productivity at a 17.5% decrease in costs by using chain saw (Phillip 2001). However, facts were lacking to establish if the perceived increase in productivity in the private regime was hand in hand with improved working conditions. There was no evidence however, to whether the private companies introduced any new technology in timber harvesting in Tanzania. To pursue this knowledge gap, a study was carried out to assess working conditions, physical workload and productivity in logging operations under private logging companies at Sao Hill Forest Project Plantations, essentially to support or dispute the positive correlation of the three working elements.

2. Materials and methods – Materijal i metode 2.1 Description of the study area – Opis podru~ja istra`ivanja This study was carried out in Sao Hill Forest Plantations (SHFP) with a significant number of private logging companies and a respectable volume of timber harvesting compared to other forest plantations in the country. SHFP supply wood to about 500

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small, fixed and mobile sawmills and to four big companies namely Mena Wood Company (MWC), Sao Hill Timber Ltd (SHTL), Mufindi Paper Mills (MPM) and Sao-Hill Industries. Two companies, Mena Wood Company (MWC) and Sao Hill Timber Ltd (SHTL) were sampled for this study because they carry out significant logging activities in these plantations.

Sao Hill plantation forests cover about 135,000 ha of land, of which about 45,000 ha have been planted (Sumari 2008, Mandalo 2010 Personal Communication). The main tree species planted are Pinus patula, P. eliotii, P. caribea, P. cassia, Eucalyptus saligna, E. maidenii, E. grandis and Cupressus lusitanica. The mean annual increment (MAI) for Pinus species is 20 m3/ha with a rotation age of 25 years, while MAI for Eucalyptus species is 25 m3/ha with a rotation age of 10 years (MLNRT 1989, Sumari 2008). The allowable cut per year is estimated to be 1,000,000m3 for the period 2008/09 and 2009/10 (Sumari 2008, Mandalo 2010, SHFP Planning officer personal communication).

SHFP is located between latitudes 8°18’–8°13’ S and longitudes 35°06’–35°20’ E in the southern highlands of Tanzania, Mufindi district, Iringa region.

The plantations are on rolling terrain interacted with some low hills and wide flat-bottomed valleys at an altitude varying from 1,400 to 2,000 m above sea level (Fue et al. 1999). The climate is characterised by rainy season from November to April and dry season from May to late October. The mean annual rainfall is 1,300 mm ranging from 725 mm to 1,400 mm.

The temperatures are fairly cool, the mean monthly minima vary between 10° to 18°C and maxima varying between 23° to 28°C (Migunga 1996).

2.2 Data collection – Prikupljanje podataka The study used two sets of data collected in different timber harvesting regimes. This information involved office records and publications for the public regimes that were available in the logging company. Another set of information was collected for the current private regime. However, it also involved collection of some data from the existing records. The data sets collected for these two regimes of the state owned and private owned were about 11 years apart. For the current regime, the data were collected in the compartment number S16 b–P76 of a 26 years old Pinus patula stand, which was being clear felled by Mena Wood Company (MWC) and Sao Hill Timber Limited (SHTL). This compartment had a total of 76 ha.

Time studies were performed for tree cutting, skidding, manual bunching and loading in order to Croat. j. for. eng. 31(2010)1

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establish production rates. It involved recording productive and non-productive work element times in centiminutes using a continuous snap-back timing method. Data were also collected for ground slope in percentage using a clinometer, skidding and manual bunching distances in metres using speedometer of the tractor and measuring tapes respectively; log mid-diameter and length were measured using a calliper and measuring tape respectively.

Physical workload was determined by measuring heart rate of the logging crews by using Polar Sport Tester. The recording of heart rate of the crews was taken one at rest, and the other was the maximum reading of continuous observation during work.

The data on working conditions were obtained through ergonomic checklist (Apud et al. 1989) and through field observation. The information assessed through ergonomic checklist was administered to 45 workers (30 workers from SHTL and 15 from MWC) intended to take care of age experience and the training of the workers; quality and availability working tools; supervision, working time and break; general safety and health aspects; social security, workers’ welfare and food.

Table 1 Classification of workload based on the percentage heart rate increase Tablica 1. Klasifikacija radnoga optere}enja na osnovi pove}anja frekvencije srca

2.3 Studied crews – Istra`ivane radne grupe

Where: PHRI Percentage of heart rate increase, % WHR Work heart rate, beats/min RHR Resting heart rate, beats/min.

Tree cutting, skidding and loading crews employed by the respective companies were studied.

For tree cutting operation two crews of one-man and three crews consisting of two individuals each were studied for chainsaw and crosscut saw cutting operations respectively. On the other hand skidding was done using modified farm tractor and a crew of three men. This involved a driver, and two choker men.

The skidder involved travelling empty, choking, travelling loaded and un-choking. Logs were choked and unchoked manually and the skidding distance at an average distance of 160 m, on a 2.4% slope and load size of 0.23 m3/trip. Two men performed log bunching while loading into hauling trucks was performed manually by six people.

2.4 Data analysis – Analiza podataka Statistical analysis was performed using Microsoft Excel spreadsheet to find descriptive statistics (mean, upper and lower values) on workload and time studies. Descriptive statistics on working conditions were obtained using Statistical Package for Social Sciences (SPSS).

2.5 Classification of workload – Klasifikacija radnoga optere}enja Workloads were classified according to Grandjean (1980) i.e., into very low, low, moderate, Croat. j. for. eng. 31(2010)1

Workload Radno optere}enje Very low, resting Vrlo nisko, odmaranje Low – Nisko Moderate – Umjereno High – Visoko Very high – Vrlo visoko Extremely high – Izrazito visoko

Percentage of heart rate increase Postotno pove}anje frekvencije srca 0 0–36 36–78 78–114 114–150 Over 150

Source: Grandjean (1980) high, very high and extremely high based on the percentage heart rate increase as shown in Table 1.

The percentage of heart rate increase was calculated as shown in Equation 1.  WHR − RHR  PHRI =  ×100   RHR

(1)

2.6 Logging Productivity – Proizvodnost pridobivanja drva Logging productivity was derived from the time and motion studies of the tree cutting operation.

Multiple regression analysis was used to develop productive time models that can be used to estimate tree cutting time as a function of the selected independent variables. The models developed were then used to estimate production rates of the tree cutting crews. These equations were combined with the log volumes calculated from field measurements.

The Smalian’s formula was used to compute log volumes because it takes advantage of parabolic shapes of the specimen where many logs and sections of trees approximate this shape (Cris 1999). The formula states that the volume of a log can be closely estimated by multiplying the average of the areas of the two log ends by the log’s length, as follows:  A1 + A2  L V=  2 

(2)

Where: V the volume of the log in cubic metres, m3

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A1

the area of the small end in square metres, m2 A2 the area of the large end in square metres, m2 L the length of the log in metres, m Since productivity is frequently measured in terms of output of goods or services in a given number of »man-hour» or »machine-hours» (ILO 1979, Samset 1992), the volume produced in a given cutting operation and the time estimated from regression models were therefore used to compute productivity in m3/hr (Equation 3). ( Tvol ) × ( F ) × (60) (3) P= T Where: P productivity for a given logging operation, m3/ha total volume of all logs for a given logging Tvol operation 60 number of minutes in a workplace hour F proportion of productive time per workplace hour, (Equation 4)

T

total productive time (minutes) (estimated using the derived regression models).

100 × D (4) F= 100

Where: F a fraction measuring the proportion of productive time D delay time expressed as percentage of workplace time

3. Results and discussion – Rezultati i rasprava 3.1 Working conditions – Radni uvjeti 3.1.1 Age, experience and training of the workers Dob, iskustvo i uvje`banost radnika Most of the crews were young of an average age of 25 years. They had shorter experience averaging 2 years and lack formal training in logging and other forest operations. When compared with the public

Table 2 Response of the workers on working conditions during logging operations at Mena Wood Company and Sao Hill Timber Ltd (N=45).

Tablica 2. Odgovori radnika o radnim uvjetima na pridobivanju drva u poduze}ima Mena Wood Company i Sao Hill Timber (N = 45) Question – Pitanje

Age of the worker, years – Dob radnika, godine Working experience, years – Radno iskustvo, godine No formal training in logging/forestry Bez formalnog osposobljavanja u pridobivanju drva/{umarstvu No protective gears and auxiliary tools – Bez za{titne opreme i pomo}nih alata No safety regulations – Bez sigurnosnih pravila No first aid services – Bez slu`be prve pomo}i Exposed to any obvious accident risk – Izlo`enost o~itom riziku nesre}e Workers encountered accident on job – Radnici kojima se dogodila nesre}a na radu No prescribed breaks at work – Bez propisanih odmora pri radu No compensation against accidents and sickness – Bez naknade za nesre}e i bolesti Presence of close supervision – Postojanje ~vrstoga nadzora Poor quality of food (ugali and beans) – Hrana lo{e kakvo}e (grah) Long working time (start at 7.00 am end at 2.00 pm) – Dugo radno vrijeme (od 7.00 do 14.00) Tool handles not appropriate and liable to break – Neodgovaraju}i i neispravan alat Blunt crosscut saws and axes – Tupe {umske pile i sjekire Workers having health problem (e.g. Backache) – Radnici sa zdravstvenim problemima Late payment (at least a month waiting) – Kasne isplate (najmanje mjesec dana ~ekanja) Payment not adequate and need of improvement – Neadekvatne pla}e i potrebna pobolj{anja

68

Response,(except for age and experience of the worker), % Odgovor (osim za dob i iskustvo radnika), % Yes Range: 18–42; Mean: 25 Raspon: 18–42; Prosjek: 25 Range: 0.1-11; Mean 2 Raspon: 0.1-11; Prosjek: 2 –

100

– – – – – – – – – – – – – – –

100 80 100 100 52 100 100 21 100 80 70 54 76 94 100

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logging regime, the workers in this study were one year younger and less experienced, where experience and age of the workers were three years and 26 years old respectively (Malisa 1992). The average of 2-year work period observed in this study is an indication of high labour turnover, which may be a result of the existing working conditions, and heavy workload that sounds unfit for old age crews. According to Fue et al. (1996), younger workers tend to work faster because they are more energetic compared to older workers. However, by being less experienced and less professionally skilled they tire quickly and are therefore more vulnerable to occupational health risks.

According to (Ole-Meiludie and Fue 1990; Shemwetta et al. 2002) the lack of formal training in forestry operations may have an effect on productivity and physical workload due to poor working methods, awkward working postures and inappropriate machine maintenance techniques. Christie (2006) reported that awkward working postures with a predominance of trunk flexion, adopted for long periods during work, are very likely to lead to the development of musculoskeletal injuries. Furthermore, untrained forest workers are more exposed to hazards because their ability to make quick and intelligent decisions in dealing with hazards is limited.

3.1.2 Quality and availability of working tools Kvaliteta i upotreba radnih sredstava Logging crews were not provided with protective gears, felling levers, wedges or lifting devices (Table 2).

This means that the crews were more liable to excessive stress and accidents. The observed situation was different to that of the public logging regime, where Migunga (1982, 1996) reported that workers were given and used protective gears such as helmets, boots and gloves. As regards to logging crews, 70% complained that the quality of cutting tools (axes and saws) was poor. It was also noted that skidding ropes were old and worn out, causing lacerations to the bare hands of the crews.

3.1.3 General safety – Op}a sigurnost Assessment of safety at work showed that about 50% of the workers had suffered some kind of accident. None of the suffered individual was given a »professional« first aid services, as only 20% acknowledged the presence of safety regulations (Table 2).

Fue et al. (1999) made similar observations during the public logging regime. For example, although the average tree height was 22 m, at least 20 crews were allocated a hectare for felling at SHTL. As a result, the crews worked too close to each other (7 m Croat. j. for. eng. 31(2010)1

Dos Santos A. Silayo et al.

apart, which is lower than safe working distance of 28 m). According to Accident Compensation Corporation (2003), in tree felling, minimum safe working distance from any other person is the equivalent of twice the height of the tree being felled. This situation is most likely to result in accidents by falling trees/branches. Inadequate safety reduces work performance due to time lost as a result of forest worker waiting for recovery after an accident. To reduce this risk, companies should engage a safe number of workers in close quarters according to the actual requirements of safe working distance.

3.1.4 Supervision, working time and break Nadzor, radno vrijeme i odmori Only 21% of the workers acknowledged the presence of close supervision. This indicates that there were no established working conditions to be supervised. It was revealed that 80% of the worker/crews complained that the working time, which was between seven and eight hours per day, was too long.

The study revealed as well that despite the longer working period a day there were no scheduled breaks (Table 2). This may contribute to high labour turnover observed. According to Slappendel et al. (1993), working continuously results in fatigue, which increases accidents, illnesses, discomfort and consequently reduced productivity, and hence, high labour turnover.

3.1.5 Motivation, social security and food for the workers – Motivacija, socijalna sigurnost i hrana za radnike Tree cutting, bunching and loading crews were paid by piece rate, while skidding crews were paid per month basis. Therefore, since the same level of payment was given per tree felled, smaller trees were mostly felled compared to larger ones. As a result, felling was done haphazardly resulting into difficulties in carrying out subsequent operations like limbing, bucking and skidding. Therefore, there is a need of improving supervision and changing the payment system from wage based to task based (like volume produced), to encourage systematic production. In case of social security, it was learned that there were no compensations to accidents and sickness. Meanwhile the crews were not satisfied with the quality and quantity of the food provided and the salary (Table 2). Unfortunately, there were no responsible organs that took care of the welfare of logging crews which are mainly casual labourers. There is a need for the government to set practical rules and regulations through which the rights of the forest workers in general can be safeguarded.

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Table 3 Physical workload in logging operations at Mena Wood Company and Sao Hill Timber Ltd Tablica 3. Fizi~ko optere}enje radnika pri pridobivanju drva u poduze}ima Mena Wood Company i Sao Hill Timber Logging operation Radna operacija pridobivanja drva Tree cutting by chainsaw at MWC Sje~a motornom pilom u MWC Tree cutting by crosscut saw at SHTL Sje~a dvoru~nom {umskom pilom u SHTL Bunching manually at MWC Ru~no usnopljavanje u MWC Loading manually at MWC Ru~ni utovar u MWC Choker setting at SHTL Postavljanje om~i i kop~anje u SHTL

Heart rate at rest, beats/min Frekvencija srca u mirovanju, otkucaji/min

3.1.6 Physical workload – Fizi~ko optere}enje Results on physical workload of the logging crews are shown in Table 3.

The overall physical workload was 78% and 65% heart rate increase for crosscut saw and chainsaw respectively. The findings for chainsaw operations are closely related to the findings by Christie (2006) who conducted a field investigation of physical workload imposed on harvesters in South African Forestry.

Generally, the results showed that there was a slight increase of physical workload in the private logging regime as compared to the public logging regime which was estimated at 65% and 57% of the heart rate increase for crosscut saw and chainsaw respectively. The heart rate levels observed in this study were all higher than the 50% set as a higher level than the resting heart rate, which signifies an acceptable workload in manual material handling and repetitive tasks. This involves such work tasks as liftng, carrying, pushing and pulling of various external loads according to (Stellman 1998). Astrands and Rodah 1989, Ilmarinen 1992, Stellman 1998, Shimaoka et al. 1998, Hsin-Chieh and Mao-Jiun 2010, which suggests that the recommended Relative Aerobic Strain (RAS) is 20–35%, which is equivalent to the acceptable heart rate of 50% from the resting states during an eight hour working day.

Observations showed that crosscut saw pinching occurred often. This situation was contributed mainly by poor felling patterns which could be associated by the level of skills for the felling crews. As a result, the crews used excessive energy on trying to pull out the saw, which caused high workload in turn. Since there were no wedges, pinched saws were released manually, which involved log or tree pulling or lifting. Since Pinus tree species which were being felled are naturally characterised by sticky res-

70

Physical workload (heart rate increase), % Fizi~ko optere}enje (pove}anje frekvencije srca), % 65 78

75

70 32 69

ins and the fact that the saws were not well maintained, manual driving of the crosscut saw could have as well contributed to high workload and saw pinching.

In skidding operations, choker setting involved log lifting and/or digging a hole under the log, carrying and pushing logs in order to pass chain chokers through. This was done without using lifting tools, which increased physical workload. Results show that the maximum heart beats per minute for chocker setters was 148; this observation was much higher than the recommended maximum absolute values for men and women, which is 90–112 beats per minute in manual handling, dynamic muscular, and repetitive work (Louhevaara 1999) like this one.

The higher workload in these operations was due to inappropriate tree cutting that could not form »log bedding» and terrain characteristics, which inhibits easier log chocking or rolling activity. The number of skidding and loading crews was also found insufficient to coup with the volume and the speed of the hauling system. The managements should therefore increase the size of bunching crew and train workers in log bunching techniques, in order to reduce the workload.

Based on the physical workload classification by Grandjean (1980) as shown in Table 1, the workload in this study ranged from moderate to high, compared to moderate workload observed during public regimes. In essence, high physical workload should have reflected low productivity, but despite higher physical workload upon the workers observed in this study, the productivity was still higher than in the public logging regime. According to Bedny et al.

(2001) short-term productivity increases may be achieved at serious long-term costs of overloading the work force. On the other hand, low productivity Croat. j. for. eng. 31(2010)1

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can be the result of suboptimal exploitation of worker potential. In this study, it was learnt that the lack of alternative jobs and the fear of losing employment provides room for the private managements to exploit logging crews to produce more on »expense« of their working conditions.

3.2 Logging productivity – Proizvodnost pridobivanja drva It was observed that logging operations were performed both manually and semi-mechanized.

Tree felling and bucking was done by using chainsaw at MWC, while crosscut saw was used at SHTL. Delimbing was done by axes. Modified farm tractors performed skidding, while log bunching and loading were done manually. It was found that the average tree height was 22 m with an average Dbh of 32 cm. Bucking was supposed to be done at 4.2 m log length, although it was learnt that crews mostly use visual estimates, which through trial and error results into higher variations. In this case log lengths varied between 3.9 to 5.1 m, with an average of 4.3 m.

Logging productivity (Table 4) in these operations was higher compared to the public logging regime, where past studies showed 2.1 m3/h and 2.9 m3/h in tree cutting by crosscut saw and chain saw respectively. The production rate in loading operation was 9.1 m3/h higher by 34% when compared to the production rates during public regime. Since working conditions were inferior and workload was high, the increased productivity observed in this

study may not be due to improved working conditions and reduced workload, but rather a result of the workers’ higher engagement and placed effort in performing production tasks. Their acceptance of such conditions is the consequence of poor employment possibilities.

4. Conclusions and recommendations Zaklju~ci i preporuke 4.1 Conclusions – Zaklju~ci The working conditions in the studied private companies were inferior and physical workload was high compared to the public logging regime. The workers had no formal training in forestry or logging techniques. Therefore, they were exposed to poor working methods, awkward body posture and inappropriate tool maintenance techniques and low pays, which may not be attractive to good workers.

Therefore, this observation lead to a general conclusion that the increased productivity in private companies was not due to improved working conditions in private logging companies, but rather is a result of the workers’ higher engagement and placed effort in performing production tasks due to poor employment possibilities. Observations further showed that the managements aimed at increasing outputs with little or no efforts of improving the working conditions.

4.2 Recommendations – Preporuke Þ

Table 4 Productivity in logging operations at Mena Wood Company and Sao Hill Timber Ltd Tablica 4. Proizvodnost pridobivanja drva u poduze}ima Mena Wood Company i Sao Hill Timber Logging operation Radna operacija pridobivanja drva Tree cutting by chainsaw at MWC Sje~a motornom pilom u MWC Tree cutting by crosscut saw at SHTL Sje~a dvoru~nom {umskom pilom u SHTL Loading at MWC Utovar drva u MWC Bunching at MWC Usnopljavanje u MWC Skidding at SHTL Privla~enje drva u SHTL

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Þ

Productivity, m3/h Proizvodnost, m3/h Range Mean Raspon Prosjek 1.3–5.6

4.7

1.1–5.2

3.4

3.8–23.3

11.3

3.9–5.8

5.1

5.8–11.4

6.5

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Þ

Þ

Þ

Declining working conditions in logging operations could be improved by setting and implementing practical occupational safety and health regulations by government agencies.

The grievances of forest workers could be well presented by formulation of a forest workers’ union; Deliberate efforts are required to introduce new technology in timber harvesting in the Tanzanian forestry.

Forest workers who are currently working in the field must be imparted with professional hands on skills from instead of relying solely on the on the job learning from co-workers.

Training institutes should conduct an educational awareness on the importance of training in forestry or logging to the management of logging companies and to young men who are the major source of labour in logging operations in the country.

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5. References – Literatura Abeli, W. S., Shio, C. J., 1996: The use of oxen for ox skidding logs in plantation forests in Tanzania. Forest Record 63: 122–127.

Accident Compensation Corporation, 2003: Tree felling sites <http://www.acc.org.nz/tree-felling-site> (Accessed 26 October 2008).

Ahlback A. J., 1986: Industrial Plantation Forestry in Tanzania: facts, problems and challenges. Forest and Beekeeping Division, Dar es Salaam. Tanzania, 197 pp.

Ally, M. H. M., 1987: Production rates and costs for tractor-trailer log transportation at SUA Training Forest – Olmotonyi. Forestry Record 52: 34–35.

Apud, E., Bostrand, L., Mobbs, I. D., Strehlke, B., 1989: Guide-Lines on Ergonomic Study in Forestry. Geneva, ILO, ISBN 92–2–106957–5. Åstrand, P. O., Rodahl, K., 1986: Textbook of Work Physiology – Physiological Bases of Exercise. Third Edition. New York: McGraw-Hill.

Bedny, G. Z., Karwowski, W., Seglin, M. H., 2001: A Heart Rate Evaluation Approach to Determine Cost-Effectiveness an Ergonomics Intervention. International Journal of Occupational Safety and Ergonomics 7(2): 121–133.

Christie, C. J., 2006: A field investigation of physical workloads imposed on harvesters in South African forestry.

Dissertation submitted in fulfilment of the requirements for the Degree Doctor of Philosophy Department of Human Kinetics and Ergonomics. Rhodes University, Grahamstown, South Africa, 179 pp.

Cris, B., 1999: Common Forest Mensuration Formulae <http://sres-associated.anu.edu.au/mensuration/Brackand Wood1998/EQUATION.HTM#Volumes> (Accessed 13 March 2010).

Dykstra, D. P., 1983: Forestry labour in Tanzania: Learning, compensation and motivation. Professorial inaugural lecture. Division of Forestry, University of Dar es Salaam.

Morogoro, 204 pp.

Fue, G. E., Ole-Meiludie, R. E. L., 1989: Manual versus semi mechanized terminal operations in tractor log transportation. Forestry Record 40: 10–17.

Fue, G. E., Migunga, G. A., Ngororabanga, J., 1996: Accident and safety in logging operations at Sokoine University of Agriculture Training Forest, Olmotonyi, Arusha.

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Fue, G. E., Ole-Meiludie, R. E. L., Migunga, G. A., Shemwetta, D. T. K., 1999: Working and living conditions in a Tanzanian forest plantation logging Company. Tanzania Journal of Forestry and Nature Conservation 72(1): 66–74.

Grandjean, E., 1980: Fitting the Task to the Man: An ergonomic approach. Taylor and Francis Ltd. London, 205 pp.

Habyalimana, J. B., 1990: A productivity and an economic comparison of a skidding farm tractor and a skidding sulky in primary timber transportation at SUA Training Forest. Forestry Record 52: 20–25.

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Ilmarinen, J., 1992: Job design for the aged with regard to the decline in their maximal aerobic capacity: Part I. Guidelines for the practitioner. International Journal of Industrial Ergonomics, 53–63.

ILO, 1979: Introduction to Work Study, Third Revised Edition. International Labour Organization. Geneva, 441 pp.

ILO, 1996: Improving Working Conditions and Increasing Profits in Forestry. International Labour Office. Geneva, 79 pp.

Louhevaara, V., 1999: Physical exercise as a measure to maintain work ability. In: Ilmarinen J, Louhevaara V, eds.

FinnAge – Respect for the Aging. Action Programme to Promote Health, Work Ability and Well-being of Aging Workers in 1990–96, p. 279–283. Helsinki: Finnish Institute of Occupational Health. People and Work. Research Report 26.

Mahenge, P., 2001: A system balance in harvesting operations by a private company: A case study of Escarpment Forestry Company Ltd. Unpublished special project. Faculty of Forestry, Sokoine University of Agriculture. Morogoro, 29 pp.

Malisa, E. J., 1992: Production and physical workload of cutting crews in Sao Hill Soft wood plantations. Unpublished Thesis for Award of MSc Degree at Sokoine University of Agriculture, Morogoro. Tanzania, 125 pp.

Mayawalla, A., 1994: Structural Adjustment Policies and the Management of Soils and Forest Resources in Tanzania. A paper presented to a seminar on structural adjustment policies and management of soils and forest resources in Tanzania, 2nd–3rd August, 1994, Morogoro, 10 p.

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Migunga, G. A., 1982: Production rates and cost of different cutting methods in a Tanzania softwood plantation.

Unpublished Thesis for Award of MSc Degree at University of Dar es Salaam, Division of Agriculture, Forestry and Veterinary. Morogoro, 118 pp.

Migunga, G. A., 1996: Productivity, costs and soil disturbances by log skidding tractors at Sao Hill, Tanzania. Unpublished Thesis for the Award of PhD Degree at Sokoine University of Agriculture, Morogoro. Tanzania, 184 pp.

MLNRT, 1989: Tanzania Forestry Action Plan. Ministry of Lands, Natural Resources and Tourism, 1990/91–2007/08.

Dar es Salaam, 128 pp.

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Ole-Meiludie, R. L., Shemwetta, D. T. K., Abeli, W.S. and Silayo, D.A., 2002: Physical workload of logging and forest industry workers in Tanzanian Plantations. In: proceedings Wood for Africa Conference, 2nd–4th July 2002, Hilton College Pitermaritzburg, Kwazulu Natal, South Africa. L. Kellogg, B. Spong and P. Licht (eds). Oregon State University, USA, 179–185.

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Sa`etak

Radni uvjeti i proizvodnost privatnih i javnih {umskih poduze}a u Tanzaniji Industrijsko pridobivanje drva iz {umskih planta`a u Tanzaniji zapo~elo je sedamdesetih godina pro{loga stolje}a kada je ve}ina planta`a dostigla rotacijsku starost. Radove na pridobivanju drva obavljala su isklju~ivo javna poduze}a s radnim ekipama i radnicima koji su bili javni slu`benici i zaposlenici dr`ave. Ve}ina je {umskih poslova u tom razdoblju bila intenzivna i polumehanizirana, s niskom razinom proizvodnosti i visokim tro{kovima. Razlog tomu bili su mnogi izazovni uvjeti, koji su uklju~ivali nepovoljne radne uvjete, visoke energetske zahtjeve i relativno niske pla}e {umskih radnika. Kao na~in unapre|enja proizvodnih, radnih i `ivotnih uvjeta radne snage u {umarstvu tanzanijska je vlada u kasnim osamdesetim godinama pro{loga stolje}a odlu~ila privatizirati {umsku industriju. Privatizacijom su neka poduze}a, vezana uz {umarstvo i drvnu industriju, likvidirana ili prodana, a neka su u{la u zajedni~ka ulaganja ili su ih zakupili privatni investitori.

Istra`ivanja su pokazala da su i nakon privatizacije {umske industrije radovi na pridobivanju drva ostali radno intenzivni i polumehanizirani s malim pove}anjem proizvodnosti. Ipak, nedostajali su podaci koji bi potvrdili da li je pove}ana proizvodnost istodobno popra}ena i boljim radnim uvjetima. Tako|er nije bilo dokaza da su privatna poduze}a uvela nove na~ine pridobivanja drva u Tanzaniji. Ovo je istra`ivanje provedeno s namjerom da se procijene i usporede radni uvjeti, fizi~ko optere}enje i proizvodnost pridobivanja drva u privatnim i dr`avnim ili javnim {umskim poduze}ima. Istra`ivanje je provedeno u {umskim planta`ama Sao Hill, podru~ju s najve}im povr{inama {umskih planta`a i posa|enih vrsta lista~a i ~etinja~a. Podru~je se nalazi na ju`nim brdskim dijelovima zemlje gdje oko 500 malih, fiksnih i mobilnih pilana prera|uje drvo s planta`a. Podaci su prikupljeni u ~istim sje~ama borovih sastojina (Pinus patula) starim 26 godina. Radove su obavljala dva {umska poduze}a ~ije su radne ekipe pra}ene u istra`ivanjima. To su poduze}a Mena Wood Company (MWC) i Sao Hill Timber Limited (SHTL).

Za sje~u, ru~no usnopljavanje i utovar drva izra|ena je studija vremena. Sje~a je obavljana na dva uobi~ajena na~ina, motornom pilom i dvoru~nom popre~nom {umskom pilom. Promatrana su dva rukovatelja motornim pilama i tri radne ekipe (sve s dva radnika) s dvoru~nim {umskim pilama. S druge strane privla~enje je obavljala ekipa od tri radnika pomo}u adaptiranoga poljoprivrednoga traktora. To uklju~uje voza~a traktora i dva pomo}na radnika na kop~anju. Dva su pomo}na radnika vezivala izra|ene sortimente u snopove, dok je utovar u prikolicu za vu~u ru~no obavljalo {est radnika koji su tako|er obuhva}eni istra`ivanjima. Mjerenja su obuhvatila prsni promjer stabala, visinu stabala i duljinu trupaca. Podaci o fizi~kom optere}enju radnika dobiveni su mjerenjem frekvencije

Croat. j. for. eng. 31(2010)1

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Working Conditions and Productivity Under Private and Public Logging ... (65–74)

srca pomo}u prijenosnoga elektroni~koga pulsomjera. Stajali{ta i fiziolo{ka opa`anja radnika dobivena su iz ergonomskoga upitnika koji je ispunilo 45 radnika. Podaci su analizirani u programu Microsoft Excel i u softverskom paketu za dru{tvene znanosti (Statistical Package for Social Sciences – SPSS).

Rezultati pokazuju da proizvodnost pri sje~i iznosi 4,7 m3/h za motornu pilu i 3,4 m3/h za dvoru~nu {umsku pilu. Pokazatelji za vezivanje i utovar iznose 5,1 m3/h odnosno 11,3 m3/h. Takvi nalazi upu}uju na ve}u proizvodnost privatnih poduze}a u usporedbi s onom postignutom u dr`avnima. Radni su uvjeti op}enito lo{i s niskom razinom sigurnosti, neprimjerenim pla}ama radnika, nedostatnim radnim sredstvima te zna~ajnom fluktuacijom radne snage. Ista je situacija postojala i u dr`avnim poduze}ima, {to govori da se nisu dogodile o~ekivane promjene i pobolj{anja. Nitko od radnika, ni u kojem obliku, nije pro{ao stru~no osposobljavanje za rad u {umi. Naprotiv, od novoanga`iranih radnika i ekipa se o~ekuje da u~e od iskusnijih na terenu.

Procjena razine sigurnosti pri radu je pokazala da je oko 50 % radnika iskusilo neki oblik nesre}e i ozljede na radu. Nitko od ozlije|enih nije primio profesionalnu prvu pomo}, a samo ih je 20 % navelo postojanje odre|enoga oblika sigurnosnih pravila pri radu. Nadalje, utvr|eno je da se pridobivanje drva obavlja bez ~vrstoga i stru~noga nadzora. Procjena je fizi~koga optere}enja pokazala zna~ajno pove}anje frekvencije srca kod svih radnika i ekipa odnosno radova. Fizi~ko optere}enje iznosi 78 %-tno pove}anje frekvencije srca pri sje~i dvoru~nom pilom i 65 % pri sje~i motornom pilom. Takvi rezultati pokazuju blago pove}anje fizi~koga optere}enja radnika u privatnim poduze}ima u odnosu na ono od 65 % i 57 % utvr|eno u dr`avnim poduze}ima. Op}enito fizi~ko optere}enje utvr|eno ovim istra`ivanjem ve}e je od prihvatljive razine 50 %-tnoga pove}anja frekvencije srca iznad razine u mirovanju kod ru~nih radova.

Rezultati pokazuju postojanje ve}e proizvodnosti u privatnim {umskim poduze}ima nego u dr`avnima.

Me|utim, pove}anje proizvodnosti nije posljedica pobolj{anih radnih uvjeta, ve} je rezultat sna`nijega anga`iranja radnika i ulo`enoga truda u obavljanje radnih zadataka, a sve zbog op}enito lo{ih mogu}nosti zapo{ljavanja. Za unapre|enje stanja preporu~uje se primjena i pridr`avanje sigurnosnih i zdravstvenih pravila u {umarstvu. Tako|er se isti~e va`nost stru~noga osposobljavanja te preporu~uje nabava i primjena sigurnosne opreme, stru~ni nadzor radova, pobolj{anja u pla}anju i socijalnom standardu radnika kao na~in unapre|enja {umske proizvodnje i smanjenja rizika pri {umskom radu.

Klju~ne rije~i: {umarstvo, pridobivanje drva, sigurnost pri radu, fizi~ko optere}enje, tro{kovi, Tanzanija

Authors' address – Adresâ autora: Dos Santos A. Silayo, MSc. e-mail: Ernest W. Mauya, MSc. e-mail: Sokoine University of Agriculture Department of Forest Engineering P.O Box 3012, Morogoro TANZANIA Said S. Kiparu, MSc. e-mail: Faculty of Forestry and Nature Conservation P.O Box 3009, Morogoro TANZANIA

Received (Primljeno): May 27, 2010 Accepted (Prihva}eno): June 16, 2010

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Assoc. Prof. Dunstan T.K. Shemwetta, PhD. e-mail: Nelson Mandela Institute of Science and Technology P.O Box 447, Arusha TANZANIA Croat. j. for. eng. 31(2010)1

Orginal scientific papers – Izvorni znanstveni radovi KARL STAMPFER, THOMAS LEITNER, RIEN VISSER Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding ..................... 1 U~inkovitost i ergonomske prednosti kori{tenja radijski upravljanih spojnih kop~i pri izno{enju drva `i~arama SERENA SAVELLI, RAFFAELE CAVALLI, SANZIO BALDINI, RODOLFO PICCHIO Small Scale Mechanization of Thinning in Artificial Coniferous Plantation .............................. 11 Privla~enje drva lakom mehanizacijom u proredama crnogori~nih kultura ATINÇ PIRTI, KUTALMIŞ GÜMÜŞ, HALIL ERKAYA, RAMAZAN GÜRSEL HOŞBAŞ Evaluating Repeatability of RTK GPS/GLONASS Near/Under Forest Environment ....................... 23 Ocjenjivanje ponovljivosti sustava RTK GPS/GLONASS u neposrednoj blizini {umskoga podru~ja YURI GERASIMOV, VASILY KATAROV Effect of Bogie Track and Slash Reinforcement on Sinkage and Soil Compaction in Soft Terrains .............. 35 Utjecaj polugusjenica i zastora granjevine na dubinu kolotraga i zbijanje tla pri izvo`enju drva forvarderom na tlu ograni~ene nosivosti AKBAR NAJAFI, AHMAD SOLGI Assessing Site Disturbance Using Two Ground Survey Methods in a Mountain Forest ...................... 47 Procjena o{te}enja stani{ta primjenom dviju terenskih metoda opa`anja u planinskim {umama TOLGA OZTURK, MUHITTIN INAN, ABDULLAH E. AKAY Analysis of Tree Damage Caused by Excavated Materials at Forest Road Construction in Karst Region ......... 57 Analiza o{te}enja dube}ih stabala pri izgradnji {umskih cesta u kr{kom podru~ju Turske

Preliminary notes – Prethodno priop}enje DOS SANTOS A. SILAYO, SAID S. KIPARU, ERNEST W. MAUYA, DUNSTAN T. K. SHEMWETTA Working Conditions and Productivity Under Private and Public Logging Companies in Tanzania ............. 65 Radni uvjeti i proizvodnost privatnih i javnih {umskih poduze}a u Tanzaniji

ISSN 1845-5719

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