The effect of altitude on lichenometry and dendrochronology at an intra- glacial foreland scale by Richard Selwyn Jones

The effect of altitude on lichenometry and dendrochronology dating methods at an intraglacial foreland scale: Tsidjiore Nouve, Valais, Swiss Alps Richard S. Jones 2008

Presented as part of the requirement for an award, in the Field of Physical Geography with Environmental Science within the Undergraduate Modular Scheme at the University of Gloucestershire, April 2008.

Acknowledgements

Data collection in the Swiss Alps was assisted by the transport and company of A. Gilding and J. Stopps, in addition to the man-power of L. Hancock and L. Prynne with help of the Leica d-GPS. Furthermore I am grateful for the support provided by S. Capron and B. Ella, and the advice of A. Bauder on the glacierâ&#x20AC;&#x2122;s fluctuation and B. Moore on GIS issues. I also greatly appreciate the expertise and guidance of P. Toms throughout this project and in the improvement of this manuscript.

Abstract

The Quaternary biological dating methods of lichenometry and dendrochronology are chronological tools often used in association with glacial geomorphology. Environmental variables are recognised as limiting the accuracy and precision of these methods, and have led to a refinement in procedures. Although altitude is understood to be a factor, it is often ignored in intra-foreland dating. This study primarily assesses the inter- and intra-moraine variations in lichen growth rates and tree ecesis with respect to absolute altitude. The foreland under investigation was that of Glacier de Tsidjiore Nouve. A glacier fluctuation reconstruction provides an indication of the deposition and exposure dates of the moraines. This fluctuation chronology was then correlated with the positions of the sampled data, mapped in 3D. The growth rate is calculated from a determination of the lichen colonisation lag. A differentiation between the substrate exposure date and ring-inferred tree age provides an ecesis period. The dates of the moraines and the areal treeline for Tsidjiore Nouve are reviewed. It was found that lichen growth rate decreased and variance increased with altitude, with an apparent threshold at ca. 2290-2300 m a.s.l. Dendrochronological impacts were minimal; however the tree height relative to girth did show a significant decrease with altitude. Implications of this study lie with the identification that altitude can affect the reliability of a lichen-derived substrate age.

Contents

1. Introduction

2. Literature Review

2.1. Establishing chronologies in glacial forelands

2.2. Lichenometry

2.3. Dendrochronology

2.4. Coupled lichenometry and dendrochronology studies

2.5. Caveats

2.6. Surveying and analysis of glacial geomorphology

3. Study Site

4. Methodology

4.1. Lichenometry

4.2. Dendrochronology

4.3. Establishment of altitudes and surveying of foreland

4.4. Data constraints

4.5. Formulating of data

5. Results

5.1. Glacier fluctuation reconstruction

5.2. Lichenometry

5.3. Dendrochronology

6. Discussion

6.1. Fluctuation chronology

6.2. Lichenometry

6.2.1. Modelling growth rate with altitude â&#x20AC;&#x201C; Implications

6.3. Dendrochronology

6.4. Future work and improved research

7. Conclusion

References

Appendices

Appendix 1 – Glacier de Tsidjiore Nouve fluctuation data

Appendix 2 – Lichenometry data: Moraine 1, 2 and 3

Appendix 3 – Dendrochronology data: Moraine 2 and 3

Appendix 4 – Treeline data

Figure and Tables

Figure 2.1.

Useful age range of selected dating methods commonly used in glacial geomorphological studies.

Figure 2.3.1. A schematic representation of the high altitude treeline ecotone.

Figure 3.1.

Study site location.

Figure 4.1.1. Technique of data collection for lichen sampling.

Figure 4.3.1. Tsidjiore Nouve foreland shown as the surveyed moraines and current glacier front. 29 Figure 5.1.1. Reconstruction of Glacier de Tsidjiore Nouve frontal positions from 2007 to initial deposition of moraine 1.

Figure 5.1.2. Continued reconstruction of Glacier de Tsidjiore Nouve frontal positions to the initial deposition of moraine 2.

Figure 5.1.3. Continued reconstruction of Glacier de Tsidjiore Nouve frontal positions to the surveyed initial deposition of moraine 3.

Figure 5.1.4. The 1995 glacier position overlaid onto an aerial photo.

Figure 5.1.5. The 1988 glacier position overlaid onto an aerial photo.

Figure 5.1.6. The 1977 glacier position overlaid onto an aerial photo.

Figure 5.1.7. The 1964 glacier position overlaid onto an aerial photo.

Figure 5.1.8. Graphic representation of the length change data.

Figure 5.1.9. Glacier de Tsidjiore Nouve foreland with lichen transects displayed.

Figure 5.1.10. Glacier de Tsidjiore Nouve foreland with sampled trees displayed.

Figure 5.2.1. A ‘black’ and ‘green’ site comparison.

Figure 5.2.2. Moraine 1: Plot of the correlation between altitude and intrasample point percentage variance.

Figure 5.2.3. Moraine 2: Plot of the correlation between altitude and intrasample point percentage variance.

Figure 5.2.4. Moraine 3: Plot of the correlation between altitude and intrasample point percentage variance.

Figure 5.2.5. Collective sample point growth rate data plotted against absolute altitude.

Figure 5.2.6. Corrected sample point growth rate data against altitude.

Figure 5.2.7. Sample point percentage variance against altitude.

Figure 5.3.1. Moraine 2: Correlative plot of sampled tree altitude against the age difference between its ring count and estimated exposure age.

Figure 5.3.2. Moraine 3: Correlative plot of sampled tree altitude against the age difference between its ring count and estimated exposure age.

Figure 5.3.3. The increase of girth in relation to height with increased altitude, for the two tree-occupied moraines.

Figure 6.2.1.1. Gurnell & Clarke’s lichen growth curve for Val d’Herens, Valais, Switzerland. 54 Figure 6.2.1.2. Val d’Herens linear growth rate against intra-foreland growth ‘curves’ for three different altitudes.

Table 2.2.1.

Some examples of lichenometric dating applications.

Table 6.2.1.

Available data of altitude-relevant climatic variables.

R. S. Jones, 2008

Chapter 1 – Introduction

1. Introduction

The Quaternary has hosted the most recent high magnitude and frequency glacial events. Cryogenic forces have high erosive potential which subsequently results in depositional features, becoming evident with the retreat of ice masses. Identification and dating of glacial geomorphology can be an indication of recent glacial history and associated climatic trends; whether at a global or regional scale. The Swiss Alps currently have just one glacier advancing out of 120 (VAW, 2008). The last significant uniform advance in the Alps occurred during the Little Ice Age (LIA). This dissertation focuses on relatively small changes in a glacier’s balance, reflected in its depositional moraines, with a time span of <150 years.

Ecological succession is observed on deglaciated terrain (Matthews, 1992), to which the biological dating methods of lichenometry and dendrochronology are owed. Lichenometric dating was developed in the Alps, for the purpose of glacial foreland features by Beschel (1950, 1957, 1961). The determination of the age of a substrate (deposited or exposed) with the use of lichen has been widely adopted, with several studies evaluating and reviewing methodologies (Beschel, 1973; Locke et al., 1979; Innes, 1983, 1985, 1986; Jomelli et al., 2007). A key assumption is made that the substrate is free of lichen when deposited or exposed and subsequent colonisation occurs shortly afterwards (Locke et al., 1979). It is known that “lichen growth can be affected by many environmental variables, including substrate lithology and roughness, moisture availability, aspect, and duration of snow cover” (O’Neal &

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Schoenenberger, 2003, p. 1); however taking these factors into account little research has acknowledged the significance of altitude. Those studies evaluating this variable (Haines-Young, 1983; Matthews, 2005) have focused on inter-foreland comparisons; at an intra-foreland level, research has recognised a relative moraine elevation effect (Haines-Young, 1983; Innes, 1986). The primary aim of this dissertation is to highlight the affect of absolute altitude on lichen growth upon three regressive moraines of a single foreland site; Tsidjiore Nouve.

The second highly documented biological dating method is dendrochronology. This technique calculates the age of geomorphological features from pairs of tree growth rings, representing annual growth since colonisation (Cook & Kairiukstis, 1990; Winchester et al., 2000). Although from a different biological kingdom to lichen, trees are subjected to similar environmental factors in order for high growth productivity and successful colonisation. Altitude is a limiting factor which is best explained by the tree line (Stevens & Fox, 1991). The foreland of Glacier de Tsidjiore Nouve is located at the limit of the favourable habitat conditions, proximal to the tree line. Colonisation of trees and growth-ring anomalies with respect to possible altitude stress will be assessed as further factors of the reliability of biological dating techniques.

Aims and objectives: The primarily intention is to evaluate the biological dating techniques, with reference to altitude on the moraines of Tsidjiore Nouve on an intra-foreland scale. Achievement of this will be possible with: 1. Establishment of a rate of retreat/advance;

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R. S. Jones, 2008

Chapter 1 â&#x20AC;&#x201C; Introduction

2. Glacier fluctuation reconstruction with determination of the relative moraine positions; 3. Identification of lag-time for lichen colonisation; 4. Intra- and inter-moraine analysis from sample-substrate exposure correlation; 5. Detection of lichen growth rate variations related to altitude, including sample accuracy and precision; 6. Detection of ring-count variation with exposure age related to altitude, while recognising distal and proximal slope, and crest differentiation; 7. Identification of tree girth and height relationships with altitude. Additionally, the age of the moraines and the elevation of the treeline will be determined and related to research thus far.

The species of lichen and tree to be assessed are Rhizocarpon geographicum and Larix decidua (European Larch), respectively, found abundantly in this alpine region and used for dating in numerous research. The correlative control is gained from Swiss Glacier Monitoring Networkâ&#x20AC;&#x2122;s 1880-2007 length change variation data, combined with GPS positioning of the data, mapping the geomorphology. A constraint on this data is photographic evidence of 1964-2001 aerials, to anchor the retreat-positioning calculations. Analysis and discussion can be conducted subsequent to the representation and correlation of the sampled data with the glacier fluctuation chronology and signified substrate exposure dates. Dates of the moraines have previously been documented by RĂśthlisberger & Schneebeli (1979), Small (1983), and Whalley (1983), to which this study will review.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

2. Literature Review

2.1 Establishing chronologies in glacial forelands

â&#x20AC;&#x153;Reconstruction of recent glacial history constitutes an important element to understanding past and present-day climatic trendsâ&#x20AC;? (Pelfini et al., 2005: 1). The erosional and depositional pattern left by a previous glacial presence is well documented at greater-than millennial scales through modelling and mapping of Pleistocene palaeoenvironments (e.g. Boulton et al., 1977). Interpretation over these intervals provides a basis for understanding glacial activity on sub-millennial scales. Conversely, observation and analysis of recent and present glaciology and glacial geomorphology (c.f. Hubbard & Glasser, 2005) can provide an analogue for palaeoinference. Currently it is possible to reconstruct annual and decadal glacier variations with an assortment of historical documents and field techniques. These methods provide a recent record from remote sensing (Dowdeswell, 1986) and geomorphic mapping (e.g. Brown et al., 1998; Anderson et al., 1998; Yingkui et al., 2001), identifying frontal fluctuations and foreland characteristics.

While it is possible to understand glacial processes and variation from modern observation, those beyond historical records require dating. There is a large variety of evidence contained within a previously glaciated environment that can give an indication of past glacier fluctuations, both biotic and abiotic in nature. Lowe & Walker (1997: 237) recognise three categories of dating techniques: those that

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Chapter 2 – Literature Review

provide age estimates, others that establish age-equivalence, or those that “establish the relative order of antiquity”. The classification of techniques is more commonly divided into numerical absolute age and relative age estimates. The absolute age of glacigenic deposits can be acquired from radiocarbon dating of

C decay (e.g.

Hubbard, 1997), thermo- or optically stimulated- luminescence dating (e.g. Richards, 2000), and cosmogenic nuclide exposure-dating (e.g. Brook et al., 1996). Alternative methodology, to provide a temporal sequence of deposition correlating a series of events, include intact rock strength (Selby, 1980), weathering rind thickness (Porter, 1975) and weathering solution pits (Fahey, 1986) as relative-age techniques, in addition to lichenometry (Beschel, 1950) and dendrochronology (Cook & Kairiukstis, 1990).

At this point it is important to understand the reliability factors of accuracy and precision, best explained by the analogy: “a precise watch that tells the time to the nearest second may still be inaccurate by 10 minutes, an imprecise watch with no second hand may still be accurate and tell exactly the correct time” (Pilcher, 1991: 28). Both of these factors represent statistical uncertainty and bias, which become increasingly apparent with progressive time before present, indicated by the limitations of acceptable dating technique resolutions (see Fig. 2.1).

Biological dating involves the existence of organic material, using the methods of radiocarbon dating, lichenometry and dendrochronology. The use of these is highly documented where there is an absence of historical records. Whereas

C dating is

useful outside the limits of the other two, on pre-colonised terrain or at high altitude, it exhibits weak precision over the last five centuries; a period particularly applicable

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

for dendrochronology and lichenometry (Jomelli et al., 2007). These two methods are based on time-dependent biological processes, and essentially reflect ecological succession on freshly revealed glacier forelands (Matthews, 1992).

Fig. 2.1. Useful age range of selected dating methods commonly used in glacial geomorphological studies (Hubbard & Glasser, 2005).

2.2 Lichenometry

Lichenometry uses the epipetric nature of lichens to determine the age of deposits. The technique has advantages over the other biological methods, in that it has higher precision than radiocarbon dating during more recent time, and that in arctic-alpine environments it can be used above the treeline where dendrochronology is not viable (Benedict, 1967). Lichenometry was conceived and initially tuned by Beschel (1950; 1961), who based it on slow-growing and near-immediate establishment characteristics, stating that â&#x20AC;&#x153;lichens may be just as old as the rock surface itselfâ&#x20AC;? (Beschel, 1973: 303). Lichens exist as a symbiotic relationship between a fungus and an alga, with its main features being an apothecium, prothallus and an areola (cf. Runemark, 1956; Gilbert, 2000).

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Chapter 2 â&#x20AC;&#x201C; Literature Review

Of the two basic principles, lichen establishment and growth rate, the former requires the substrate to be lichen-free at exposure, the rate of colonisation to be known, and establishment of a relative chronology of substrate; the latter requires development to be a direct function of age, the rate of growth to be known or ascertained, and the growth to be linear during the considered time-span (Worsley, 1990a). Most commonly used in lichenometry are the yellow-green crustose lichens of the Rhizocarpon subgenus; although other species including Placopsis perrugosa (Winchester & Harrison, 2000) and Xanthoria elegans (Osborn & Taylor, 1975) are also used. Rhizocarpon geographicum in particular is found abundantly in many cold arctic-alpine environments, on surfaces of Holocene age and usually at altitudes comparable between sites. It is typically the first coloniser, with a slow growth of about 0.02-2.00 mm yr-1 (Porter, 1981; Innes, 1985a).

A relationship between the diameters of established lichen thalli and the time since colonisation is required in dating surfaces of unknown age. This association can be in the form of the measurement of thalli on dated substrates (Jomelli et al., 2007) or a recorded growth rate (Karlen & Black, 2002); the latter producing a growth curve with an increased accuracy of growth rates. It is known that the period after which lichen becomes visible, there occurs an acceleration in growth (Beschel, 1950). This is the case until a certain diameter is reached, predominantly past a 300-year age beyond the requirement of most lichenometric studies (Webber & Andrews, 1973: Table 2), where growth rates decrease with increasing age represented both linearly and exponentially (Porter, 1981).

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

The original method (Beschel, 1950), so far explained, uses a size/age correlation of the maximum thallus diameter. It has been used successfully by Orombelli & Porter (1983) in the Italian Alps, amongst others. However, applying the largest diameter has proven inaccurate in many circumstances (e.g. Locke et al., 1979; HainesYoung, 1983; Jomelli et al., 2007). The largest inscribed circle equivalent to the smallest diameter was proposed by Locke et al. (1979) with occasional subsequent use (Luckman, 1977). An alternative averaging approach has been preferred by Matthews (1974; 1975) and Innes (1984), based on either the 5 or 10 largest, or mean of 30 (McCarrol, 1994). While precision is realistically estimated to ± 1mm (Innes, 1985a), an associated error is considered to be varied from >15mm (Andrews & Barnett, 1979) to <1mm (Porter, 1981). Modern statistical approaches, including multiple averages (Nikonov & Shebalina, 1979), Gaussian distribution (McCarrol, 1994), and Bayesian and Extreme Value Theory methods (Naveau et al., 2005; Cooley et al., 2006), have improved the confidence of mean accuracy and variance in the context of sampling error.

A second method, developed by Benedict (1967), considered lichen size-frequency distributions and focused on the density-dependency of populations. Locke et al. (1979) included a “1 in 1000” thallus calculation. However this was subsequently criticised (Innes, 1983). A combination of both size/age and size-frequency techniques can also prove beneficial (Winchester, 1989). Lichenometry has many aspects which have sparked discussion and debate (e.g. Webber & Andrews, 1973; Jochimsen, 1973; Locke et al., 1979; Innes, 1985a), and “this variability among lichenometry procedures used during the last 50 years clearly indicates the absence

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Chapter 2 â&#x20AC;&#x201C; Literature Review

of a methodological consensus among geomorphologists for deriving the dates of surfacesâ&#x20AC;? (Jomelli et al., 2007: 132).

The method has been applied to various types of surfaces worldwide (see Table 2.2.1). Glacially formed moraines are the dominant subjects for the dating procedure; Orombelli & Porter (1983) and Pech et al. (2003) being examples from the European Alps.

Table 2.2.1. Some examples of lichenometric dating applications. Type of surface River channels Rock glaciers Protalus ramparts Debris flows Landslides Statues Earthquake-induced rockfalls Moraines

Location England Swiss Alps Norway Swedish Lapland Italian Alps Easter Island Middle Asia Iceland Norway Greenland Patagonia New Zealand Kenya

Author(s) Macklin et al. (1992) Haeberli et al. (1979) Shakeby et al. (1987) Nyberg (1985) Porter & Orombelli (1981) Follman (1961) Nikonov & Shebalina (1979) Bradwell et al. (2006) Matthews (1977; 2005) Beschel (1961) Winchester & Harrison (1994; 2000) Lowell et al. (2005) Spence & Mahaney (1988)

2.3 Dendrochronology

On glacier forelands which descend below the treeline, typically in relatively temperate maritime regions, an alternative dating technique of dendrochronology can be applied. In this situation a pattern of annual tree growth can be recognised. Acknowledged by Matthews (1992), with respect to recently deglaciated terrain, the procedure requires determinations of the age of the living trees, any date interruptions to the normal growth pattern, and dates of establishment, death or

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

growth-rate variation. This application to glacier forelands is often used to provide a minimum date for deposition, with the example of moraine formation, occurring during glacier fluctuations, and is termed â&#x20AC;&#x2DC;dendroglaciologyâ&#x20AC;&#x2122; (cf. Hubbard & Glasser, 2005). Other variations include dendroclimatology and forms of ecological analysis (Cook & Kairiukstis, 1990; Wimmer & Vetter, 1999).

The growth pattern is of importance throughout dendrochronology. During a given growth period there is an addition of secondary woody tissue, initially produced as large thin-walled cells before a transition to small thick-walled cells (Worsley, 1990b). Active periods of radial growth are followed by dormant ones, formulating a cyclic pattern in which identifiable tree rings occur as discontinuities. The cycles are normally seasonal (summer/winter) giving an indication of annual events. In the context of tree development, the rings form successive cones of growth; producing an increasing width and height (Stokes & Smiley, 1996). As tree rings are therefore representative of age, counting the rings from the central pith to the outer bark provides a year-year date. Chronologies can be constructed for more than 1000 years on glacial forelands (e.g. Osborn et al., 2001). Cross-dating correlations eradicate anomalies from possible sensitive ring patterns, furthered with comparison to a regional master record chronology. Pilcher et al. (1984) devised a master chronology for Europe from a convergence of records and projects, producing an absolute timescale back 7272 years.

Inaccuracies mostly derive from methodological ambiguity, with the example of locating the oldest tree (Luckman, 1986) or the determination of tree establishment (ecesis) (Winchester & Harrison, 2000). Due to the association of climate with tree

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R. S. Jones, 2008

Chapter 2 – Literature Review

development,

quantified

from dendroclimatology, an effect on ecesis and growth is

exemplified

climatically-sensitive

at high

latitudes and altitudes (Innes, 1991). The treeline provides Fig. 2.3.1 A schematic representation of the high altitude treeline ecotone (Körner & Paulsen, 2004).

a relatively sharp transition at which a reduction in tree

growth occurs beyond a certain altitude (Paulsen et al., 2000). The transition zone (treeline ecotone) encompasses the closed forest “timberline” to the “outpost treeline” (Paulsen et al., 2000) or the upper “krummholz” belt (fig. 2.3.1), where there is increased sporadicity (Körner, 1998). Treter (1984) identified the climatic effect as a decreased ring width with increased altitude into the upper 100 m of the ecotone. Within the Swiss Alps, Gams (1931) pioneered research into treelineclimate relationships, and where human activity has not reduced the treeline it is recorded to reach 2250-2300 m.a.s.l. in central Valais (Carnelli et al., 2004b).

Dendrochronology has been applied widely to glacial geomorphology where there is a direct affect via primary colonisation. Luckman (1977) used the technique on a synchronous landform occurring through the treeline. Indirect application can be achieved from correlating ring width and environmental stress with glacier fluctuations (Matthews, 1977). Pelfini et al. (2005) included both types of method to identify a glacier’s recent history and climate trends in the European Alps.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

2.4 Coupled lichenometry and dendrochronology studies

An advantage of obtaining ages below a treeline results in more accurate multi-proxy dates, as the techniques of lichenometry and dendrochronology can be used together. Oâ&#x20AC;&#x2122;Neal & Schoenenberger (2003) applied both to produce a lichenometry curve, while Winchester & Harrison (2000) and Lang et al. (1999) used them to identify geomorphological event dates.

2.5 Caveats

As with many dating approaches, assumptions have to be made and to these caveats arise. Lichenometry uses the presumption that the largest thalli on a substrate are measured and that their growth rates are constant (Winchester & Harrison, 1994). Webber & Andrews (1973) highlight 3 groups of problems: biological, encompassing the symbiotic nature, basis for taxonomy, thallus morphology and ecology, survival and dispersal, competition, and growth rate; sampling problems including incorrect identification, failure to find the largest thallus, errors in measurement, and incorrect growth curve calibration; environmental problems comprising of substrate and climatic factors. The latter of these is considered to be the hardest to control within the methodology (Innes, 1985a), limiting the reproducibility of the technique (Worsley, 1990a). The effects of slope degradation on lichenometric dating were studied by Oâ&#x20AC;&#x2122;Neal (2006). Moraines were found to widen and flatten over time with an increase of introduced boulders reducing

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Chapter 2 – Literature Review

accuracy. In this situation, there would be a multimodal rather than unimodal pattern of events (Lang et al., 1999). Substrate lithology (Benedict, 1967), moisture availability (Innes, 1985b), temperature (Kershaw, 1983), light intensity (Gauslaa, 1984), aspect (Belloni, 1973; Haeberli et al., 1979), wind exposure (Benedict, 1967) and snowcover (Haeberli et al., 1979; Porter, 1981; Sancho et al., 2001) are all considered to be significant ecological factors.

In dendrochronology, the effect of trees growing close to the treeline denotes their ecological tolerance, where it is found they are more sensitive to climate (Fritts, 1976). This effect can be represented by growth rings, of more relevance to dendroclimatology, as ‘S-rings’ opposed to ‘C-rings’ of adequate conditions (Worsley, 1990b). For direct dating purposes extreme variations in tree-ring width can lead to false or absent rings (Copenheaver et al., 2006). Although such variations can be from complex competition, disease (Lang et al., 1999) and nutrient limitations (Brown & Higginbotham, 1986), the most significant factor is climate (Innes, 1991). Temperature is the dominant variable of climate, which is apparent at the treeline as a seasonal mean temperature range between 5 and 7oC (Körner, 1998) found on a global scale (Körner & Paulsen, 2004), and which can have an indirect effect via CO 2 as a limiter of carbon investment (cf. Paulsen et al., 2000).

Ecological variations due to climatic and environmental factors are of differing magnitude at different scales; macro, meso and micro. At regional (macro/meso) scales such variations have been found with these biological dating techniques (Porter, 1981; Bradwell & Armstrong, 2007; Lang et al., 1999). Micro-environment dissimilarities are subject to local, intra-area factors, which differ between areas, and

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

are acknowledged in both lichenometry (Porter, 1981; Innes, 1985a; Sancho et al., 2001; O’Neal, 2006) and dendrochronology (Lang et al., 1999; Winchester & Harrison, 2000; Paulsen et al., 2000).

Altitude provides an affect through its influence on other variables, including precipitation, snowcover, temperature and light intensity (Innes, 1985a). While it is accepted that there is a relationship between ecological growth and hygric continentality (Gams, 1932), a lack of control over the varied altitudinal factors has led to many studies ignoring altitude altogether (e.g. Beschel, 1950; Winchester & Harrison, 1994; Sancho et al., 2001), particularly with lichenometry. Matthews’ research in Jotunheimen, southern Norway (Matthews, 1977; 2005) identified interforeland differences due to the altitudinal gradient, which was supported by HainesYoung (1983). Intra-foreland and even intra-moraine environmental variations have been recognised as having an effect on lichen size (Haines-Young, 1983; Innes, 1986); although this variation is not representative of absolute altitude, rather an optimum position on the moraine. This theory originates as the “Green zone hypothesis” (Matthews, 1977), where larger mean thalli exist at the base of the moraine at ‘green zone’ sites and smaller mean thalli and variances occur on marine crests at ‘black zone’ sites; said to be a result of buffering effects versus growth restriction (Innes, 1986). Intra-foreland environmental heterogeneity could well be limiting for dendrochronology where the glacial foreland lies proximal to the climate-sensitive treeline, delaying colonisation and affecting growth during the crucial initial stages (Rammig et al., 2007).

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Chapter 2 â&#x20AC;&#x201C; Literature Review

2.6 Surveying and analysis of glacial geomorphology

Glaciers are in dynamic states rather than stagnant, and climatic forcing affects their size and physical condition. The evolution of these ice masses is apparent from their redistribution, which can be recorded from aerial observations, Global Positioning Systems (GPS) and Geographic Information Systems (GIS) (Gao & Liu, 2001). The development of aerial photography supplied the opportunity to monitor glacier tongues from multi-temporal images (e.g. Espizua, 1986). Dowdeswell (1986) demonstrated how the finer spatial resolution and increased accuracy of aerial photos betters the use of satellite data. Ford (1984) demonstrated the potential for mapping lateral moraines, which has been furthered into more complex cross-sectional and long profile studies of glacial moraines (e.g. Yingkui et al., 2001). The introduction of differential-GPS mapping of landscapes and monitoring of glacial changes by Jacobsen & Theakstone (1997) brought a fast, accurate and precise technique. Spatial analysis of glacial forelands and variations is achievable efficiently in GIS (Li et al., 1998), aiding assessment of geomorphological measurements (Brown et al., 1998).

The spatial mapping of a variety of morainal distributions indicates past glacier fluctuations; however a temporal control is required for the dating of their formations (Benn & Evans, 1998). In the absence of multi-temporal aerial photography, dendrochronology and lichenometry become the popular controls (Hubbard & Glasser, 2005). While Moreau et al. (2005) analysed vegetation colonisation with the use of d-GPS and GIS methods, direct use between the biological dating methods and this geomorphic mapping is limited, especially for moraine studies.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Bollschweiler et al. (2006) made use of GPS with dendrochronology on debris-flow activity, and Burga et al. (2004) coupled the GPS technique with lichenometry on rock glacier surfaces. A temporal correlative control upon lichenometry and dendrochronology use on moraines is often from aerial photography (e.g. Winchester & Harrison, 1994, 2000; Evans et al., 1999). Multi-proxy records are used to establish more accurate glacial chronologies, and the application of spatial with temporal data can provide a framework for the lichenometry and dendrochronology dating techniques.

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Chapter 3 – Study Site

3. Study Site

The foreland under investigation is situated within the Arolla valley of the Val d'Hérens in the southern Swiss region of Valais, forming part of the Pennine Alps (Fig. 3.1). The fluctuations of Glacier de Tsidjiore Nouve have generated a recently deglaciated terrain; “in its lowermost section, from the base of the Pigne d’Arolla ice fall, glacier de Tsidjiore Nouve is confined between massive lateral moraine embankments” (Small et al., 1984: 275).

The relevance and significance of this site to the study is in part due to its altitudinal location (ca. 2150-2400 m.a.s.l.), with the treeline (Larix decidua) at the top of the foreland. Secondly, the moraines, which are lateral and latero-frontal dump moraines from supraglacially derived debris (Boulton & Eyles, 1979), offer distinct ridges of dateable neoglacial advance deposits (Röthlisberger & Schneebeli, 1979). These lateral moraines exist as 3 main sets, with some small nested ridges (Small, 1983), extending for about 2 km along the northern glacier margin and 1.2 km along the southern margin (Small et al., 1984). The northern side has had impacts on its morphology from glacial processes (Whalley, 1973) and winter skiing tourism. The latter has also led to clearance of trees from the older moraines. Apart from a small footpath, the south side is relatively undisturbed, showing distinct phases of the glacier’s past history.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Figure 2.1: Location of Glacier de Tsidjiore Nouve within the Swiss Alps. The foreland under investigation is circled.

Ecological succession is apparent, and staged by the successive moraines. The European Larch (Larix deciduas) is the most abundant and pioneering of the tree species on Tsidjiore Nouveâ&#x20AC;&#x2122;s marginal foreland. The Arolla/Swiss Pine (Pinus cembra) also frequents, but not to the same degree. The dominant lichen is that of Rhizocarpon geographicum, which can also be viewed as the first coloniser. General successional alpine vegetation on this foreland is characteristic of that found in the Swiss Alps (Burga, 1999; Carnelli et al., 2004a) and of cold environment moraine colonisation (Moreau et al., 2005).

In the 1980s accumulation rates from the glacier were 7,950-10,600 tonnes with the directly deposited lateral moraines making up 30-40% of this (Small et al., 1984). Geology is primarily granite with some gneiss. Haefeli (1955-56) recognised a

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Chapter 3 – Study Site

frontal velocity of 100 m year-1 during 1892-93, leading in part to the claim that it is “geomorphologically an intensely active glacier” (Small et al., 1984: 280). Röthlisberger & Schneebeli’s (1979) fossil moraine dating concluded accumulation during the past 5000 years.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

4. Methodology

The dating techniques of lichenometry and dendrochronology which are under investigation have evolved to become more acknowledging of variables and more thorough as methods. The original lichenometric technique by Beschel (1950) was followed by several evaluating papers (e.g. Webber & Andrews, 1973; Innes, 1985a; Jomelli et al., 2007), which brought alternative approaches to the methodology (e.g. Benedict, 1967; Locke et al., 1979) and statistical analysis (e.g. Cooley et al., 2006). Meanwhile, the framework for dendrochronology has remained relatively unchanged since the 19th Century in Western Europe (Cook & Kairiukstis, 1990). Developments in this technique have focused on the dendroclimatological aspects (e.g. Martinelli, 2004) and tree-ring analysis (e.g. Wimmer & Vetter, 1999).

4.1 Lichenometry

The lichens colonising the foreland of Glacier de Tsidjiore Nouve are found more abundantly with each aging moraine. For the purpose of this study, each measured lichen contributing to the dating process is classified on an inter- and intra-moraine scale within this same foreland. Intra-moraine use of the data will look at the relative altitude effects within each transect, including ‘green site’ (Haines-Young, 1983) and ‘black site’ (Innes, 1986) differences, in addition to analysis of the moraine’s sample points in relation to absolute altitude. Comparison of these intra-moraine differences

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Chapter 4 – Methodology

to the other moraines provides an inter-moraine study. Jomelli et al. (2007) proposed 3 criteria towards successful application of this technique: statistical methods should be appropriate to the type of data; accuracy of the estimated dates; precision of the estimated dates. The methodology applied in this study will attend to these three requirements.

In the field, it is vital that the correct lichen is identified for measurement. Rhizocarpon geographicum was chosen owing to its abundance and its occurrence as an early coloniser of the foreland, as well as its popularity due to higher resolution from slower growth (Porter, 1981). The technique uses the slow growth rate of lichens to identify the substrate’s age of exposure. Guidance towards identification of R. geographicum was assisted by the study of Gilbert (2000). Measurements of diameters were made using a vernier calliper. To acknowledge the possible altitudinal effects a resolution to 0.1 mm was used, even though for general lichenmetric studies it is said that ± 1 mm is the most realistic (Innes, 1985a). For the most recently established lichens, smallest excepted size was of 0.5 mm. The most circular thalli were measured to avoid composite lichens and coalesced thalli. Variation on this lichen parameter has existed, as ‘largest inscribed circle’ (Locke et al., 1979) equivalent to shortest diameter (e.g. Luckman, 1977), and the largest diameter (e.g. Proctor, 1983). A problem with the latter is a possible recording of multiple thalli. The use of circular or sub-circular thalli can be quantatively recognised by measuring the two most divergent diameters, accepting only if there is a <10% difference (Pech et al., 2003). While the most circular thalli method is widely used as the ideal (e.g. Winchester & Harrison, 1994, 2000; Pech et al., 2003), it is acknowledged that more elliptical and irregular thalli are dominant on older

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

substrates (Innes, 1985a). This aspect of sampling is unavoidably selective, but is required for optimum age-prediction.

Systematic variations occur with lichen growth rates. These are associated with ecological variables which require acknowledgment. In an ecological related study, environmental variables must be kept constant, other than that under investigation (Innes, 1985a). Oâ&#x20AC;&#x2122;Neal & Schoenenberger (2003) identified vegetation complexity and competition as an important variable to be controlled, and it has been recorded that lichen growth can be restricted by the presence of other vegetation (Ellis et al., 1981). This study followed the guidelines to measure thalli at least 1 cm from the nearest competitor (Armstrong, 2002). Although Armstrong (1992) failed to recognise aspect preference; previous research has found south-facing slopes advantageous for lichen growth (Belloni, 1973), and in the Swiss Alps north-facing inclination for R. geographicum (Haeberli et al., 1979). The moraines of Tsidjiore Nouve have a NNW aspect, which is relatively identical along the moraines.

The physical nature of the substrate is understood to be of importance within lichenometric dating (Innes, 1985a). The surface of the colonised boulder might provide variable factors to lichen growth from the degree of rock hardness and texture (Armstrong, 2002). Lichens at Tsidjiore Nouve were measured on the upper side of boulders, consistent with Pech et al. (2003). The size of boulders should be varied within the sampling programme (Lang et al., 1999), which was followed here. In periglacial environments rock structure becomes a factor (Lang et al., 1999). To avoid this impact, boulders with signs of high fragmentation were ignored. Most research using Rhizocarpon has been carried out on siliceous substrates such as

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Chapter 4 – Methodology

granite and schist (Innes, 1985a; Lang et al., 1999), although lichen preference for this lithology has been argued (Belloni, 1973; Porter, 1981). This study only measured those lichens on granite substrates, which is the dominant geology of the foreland.

The number of thalli to be measured has been a debate of statistical relevance. Several large thalli are favoured (Matthews, 1975, 1977; Innes, 1983, 1985a), with Jomelli et al. (2007) recognising a larger number sampled to bring higher accuracy. Five largest lichen thalli on three boulders at a set altitude were measured in this investigation; totalling 15 per altitudinal location on the moraine. More than one boulder provided an increased chance of finding enough lichen, particularly on the most recently exposed of moraine 1, and acknowledged possible microhabitat variation between boulders.

Slope degradation of moraines has been shown to effect lichenometry (O’Neal, 2006). Locke et al. (1979), O’Neal & Schoenenberger (2003) and Pech et al. (2003) recognise anomalies as a result of clast displacement, bringing thalli not contemporaneous with the deposit; a bi-modal distribution of thalli diameters results (Winchester & Harrison, 1994). This situation is possible with Tsidjiore Nouve’s steep moraine slopes; therefore only well-rooted large boulders were sampled at the bases of steep slope parts.

Sampling was conducted as transects along the moraines. For each moraine, a sample location was made at the toe, and then at approximately every 25 m along the moraine crest (calculated with measuring tape) from which transects were be made

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

(see figure 4.1.1). This spacing accommodates variation in the shape of the glacier front. The transects followed down the proximal side of the morainesâ&#x20AC;&#x2122; slope, directing towards the central foreland. Along each transect, kept linear with use of measuring tape, a sample location was created at every 5 m altitude change. The measurement of the 5 thalli diameters on 3 separate boulders was accomplished at each of these locations. The bottom 5 m of the moraines (especially for moraine 1) was ignored due to fluvial-influence on the central foreland. Pathways were also avoided due to possible disturbance upon growth and establishment (Innes, 1985a). The method used here was tailored to the purpose of evaluating altitude; other studies have incorporated random quadrat sampling techniques (Armstrong, 2002; Pech et al., 2003). Those environmental variables related to an altitudinal gradient, such as precipitation, temperature and snowcover (Evans et al., 1999) could not be controlled or directly observed; however proximal weather station secondary data of equal altitude and of the same valley is accessible.

Fig. 4.1.1. Technique of data collection for lichen sampling.

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Chapter 4 â&#x20AC;&#x201C; Methodology

4.2 Dendrochronology

Tsidjiore Nouve foreland is located just below the treeline. The most appropriate site for a dendroclimatological study is one where tree growth is at its climatic distribution limit (Pilcher, 1990). Although this investigation looks at the dendrochronology dating method, the evaluation of it requires the site to have altitude as a strong limiting factor. Examination of environmental gradients is achieved by selecting a site along that gradient (e.g. Norton, 1983); altitude at the treeline

ecotone.

Pilcher

(1990)

identifies

two

important

site-selection

considerations: site homogeneity which determines the quality of the chronology, where results should ideally be from the same site, as in this case, rather than collecting samples from different forelands at the same altitude; stand development affecting cambial activity, where only dominant/codominant trees should be sampled, which was conducted here and the largest/oldest tree is likely to be the most dominant (more applicable to moraine 3).

The two most abundant tree species were the Arolla Pine (Pinus cembra) and the European Larch (Larix decidua). The latter of these was more dominant and the first tree coloniser of the moraines, and was therefore selected for sampling. Identification of this species was achieved with guidance from Johnson & More (2004). Larix is recorded to have ecological and behavioural peculiarities related to being lightloving, with yearly defoliation and an efficient use of environmental resources, denoting sensitive tree-ring chronologies (Shiyatov, 1986).

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Variability occurs within a single sample tree, which is greatest at the base and smallest in the crown section, so it is advised that coring of trees is conducted at breast height (Pilcher, 1990). Winchester & Harrison (2000) recognise coring height to be a key systematic variable requiring standardisation. They refine the sample height to a minimum of 112 cm, which was used in this investigation. Paulsen et al. (2000) highlight the significance of missing the central pith in dendrochronology; therefore extra caution was given to maintaining a straight and level boring procedure. While coring with stem disks is best for excluding irregularities such as compression wood, tension wood, abrupt ring width change and wound tissue, most studies use the increment borer (Pilcher, 1990). The L. decidua of Tsidjiore Nouve were cored using the 5 mm increment borer (similarly to Winchester & Harrison, 2000; Paulsen et al., 2000). It consists of a hollow drill screwed into the trunk, with an undisturbed core left in the centre which once penetrated is removed by a semicircular tube, and subsequently the rings are counted (Worsley, 1990). Sampling avoided the vicinity of a wound or reaction wood, as well as buttress and upslope/downslope sides of trees growing on sloping ground, acknowledging Pilcher (1990).

Sampling of the individual trees does have an element of selection, as the oldest trees require coring to obtain the minimal age and not every tree can be sampled. The experimental bias and choice of oldest tree included recognition of dominance, height, trunk girth and relative development of branches against its neighbours. The â&#x20AC;&#x2DC;oldestâ&#x20AC;&#x2122; trees were selected at every significant altitude change (at least 5m), with all similar aged trees being sampled, unless limited in number where just one agealtitude sample is possible. Trees were sampled predominantly on the proximal

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Chapter 4 â&#x20AC;&#x201C; Methodology

moraine sides, although also on the crests and the distal sides, as Small (1983) and Small et al. (1984) identified secondary deposition to the distal slopes during glacier recession at Tsidjiore Nouve. Dendrochronological dating of the distal slopes would review this theory of the upper deposition of the distal and proximal moraine sides having the same ages. Additionally height and girth measurements were made for each cored tree, to give an indication of the physiology affected by altitude. Girth was measured with tape at the core height of the main trunk, while measurement was gained approximately with the arm and arm-length ruler at right-angles set back from the tree to encompass its full height, at which point the distance back to the trunk is measured; correlating to its height.

Altitude is recorded for each individual tree sampled, consistent with Winchester & Harrison (2000) and Paulsen et al. (2000). As with lichen, the altitude related variables can be observed from secondary data, which becomes supportive in the discussion (e.g. Paulsen et al., 2000). The L. decidua outpost treeline was recorded across the upper foreland, as vertical and lateral positions of the highest growing individuals. Blijenberg (1998) identifies systematic tree ring errors within his data, and concludes not to use the minimum tree ring date. Tree ring variations often result from disease and competition, in addition to climate (Lang et al., 1999), and therefore replication is required to identify the effect of the altitudinal variables. Precision with dendroclimatological studies is efficient to 0.01 mm ring width; however for dendrochronological purposes precision can not be applied to ring counts (Paulsen et al., 2000).

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

4.3 Establishment of altitudes and surveying of foreland

Every sampled tree and lichen sampling location was spatially recorded with a GarminTM handheld GPS on a 3-D scale. Laterally the position was recorded in the local Swiss Grid and global longitude-latitude projection. Vertically, the altitude was noted; however it has been observed that the elevation readings lack sufficient accuracy for handheld GPS (Winchester & Harrison, 2000). As this investigation requires accurate altitude measurements, calibration was carried out. To achieve this, a stable reference point was used (being the central support of the Tsidjiore Nouve bridge). This reference point was then recorded using the accurate and precise differential GPS (Hubbard & Glasser, 2005). First used on glacial forelands by Jacobsen & Theakstone (1997), the d-GPS technique provides a fast and efficient method, with 3-D precision calculated to 0.02 metres. The d-GPS used was a Leica 500 TM that additionally provided the surveying of the moraine crests and the front of the glacier, required for glacier fluctuation reconstruction.

Digital mapping of the foreland can be furthered with GIS analysis (cf. Gao & Liu, 2001). The surveyed data from Tsidjiore Nouve foreland was uploaded initially to Leica SkiPro TM

, before being imported into MapInfo

GIS software. In MapInfo

the data has the potential to be displayed in layers over geo-referenced maps, with

the sample data being presented thematically. From this software, the foreland parameters were converted to MIF files for export to Idrisi was necessary to a recognisable format. Once in Idrisi

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. Further conversion

, the approximate glacier

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Chapter 4 â&#x20AC;&#x201C; Methodology

front was digitised over in vector format; guidance on the position and shape of this line came from Andreas Bauder (pers. comm.) of the Swiss Glacier Monitoring Network, and photographic evidence indicating previous glacier front morphology. The distance of past glacier positions was digitally computed in Idrisi TM (Fig. 4.3.1) for every 2 years from Tsidjiore Nouve retreat data (VAW, 2008). These reconstructions were then imported back into MapInfo

for correlation with the

lichenometric transects and dendrochronology samples.

Fig. 4.3.1. Tsidjiore Nouve foreland shown as the surveyed moraines and current glacier front; computed distance from digitised glacier front line (black). Subsequent to this stage, buffer limits were established for separate retreat/advance fluctuations; every 2 years before present.

4.4 Data constraints

The reconstruction of the past glacier fluctuations, indicated from length change data since 1882, was calibrated using aerial photographs of the Arolla area. These

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

photographs, courtesy of Professor S. Lane, Geography Department, Durham University (pers. comm.), produce a multi-temporal visual record from 1964-2001. Aerial

photographs

have

been

used

previously

lichenometry

and

dendrochronology studies to act as a calibration dating framework (e.g. Winchester & Harrison, 1994; Evans et al., 1999), with some being used jointly to construct foreland maps (Winchester & Harrison, 2000). O’Neal & Schoenenberger (2003) combined historical maps, multi-temporal aerial photos, historical accounts and tephrochronology to constrain lichen and tree-ring data.

4.5 Formulating of data

Analysis of the lichen data, with regards to its accuracy, is achieved from the correlation of past glacier positions and the thus the date of exposure, with respect to transect locations. Aside from possible age differences, the precision of the measurements can be quantified from transect variances. An intra-moraine study is accomplished from within transect variations; including the bottom ‘green site’ to top ‘black site’ differences. Meanwhile comparison with the other two moraines provides the inter-moraine aspect of results. The correlation of all absolute altitudes with relative lichen-derived age accuracies and precisions, for the 3 moraines collectively, presents the intra-foreland evaluative trend. Linear growth rates formulated from glacier chronology reconstructions and sample point percentage variances are calculated against absolute altitude for lichen, with the correlation coefficient of R2 used for the strength of relationships.

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Chapter 4 â&#x20AC;&#x201C; Methodology

The ring-count of the cored tree samples aims to provide an indication of the treeâ&#x20AC;&#x2122;s age, and the difference between this and an exposure date signifies the lag of colonisation or anomalous tree rings. This is plotted against absolute altitude for each tree-occupied moraine. Additionally, the growth physiology of the trees with respect to altitude is calculated from a girth:height ratio. Similarly to the lichen analysis, R2 values are used with correlations. The outpost treeline for L. decidua is also recorded spatially.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

5. Results

5.1 Glacier fluctuation reconstruction

Glacier de Tsidjiore Nouveâ&#x20AC;&#x2122;s retreat data (VAW, 2008) has been computed with GIS software to produce progressively older glacier front positions from 2007. The reconstruction of formation of the lateral moraines and initial deposition from the moraine toes is viewable in figures 5.1.1, 5.1.2 and 5.1.3, of moraines 1, 2 and 3 respectively. The moraines are numbered with the deposition of the most recent first.

The glacierâ&#x20AC;&#x2122;s history back to the deposition of the toe of moraine 1 has been dominated by retreat; see Appendix 1 for the length change data. A phase of retreat during 1990-1993 followed the last major period advance; resultant deposition was then however overridden in 1993-1995. The year of 1995 marks the furthest most point of moraine 1, from which the retreat thereafter deposited its lateral sides. Aerial photography has aided the reconstruction, supporting the 1995 position (Fig. 5.1.4).

Glacier fluctuation previous to 1990 was of continuous advance from 1971. Reconstruction of this periodâ&#x20AC;&#x2122;s positions correlated well to the available aerial photographs. The tip of the 1988 glacier front is in accordance with the computed position (Fig. 5.1.5), but the shape of the front at this time was heavily influenced by the adjacent fluvial activity to the north side.

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Chapter 5 â&#x20AC;&#x201C; Results

Fig. 5.1.1. Reconstruction of Glacier de Tsidjiore Nouve frontal positions from 2007 to initial deposition of moraine 1.

Fig. 5.1.2. Continued reconstruction of Glacier de Tsidjiore Nouve frontal positions to the initial deposition of moraine 2. The displayed past positions are those with a resultant moraine exposure, relevant to the lichen transects and sampled trees.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Fig. 5.1.3. Continued reconstruction of Glacier de Tsidjiore Nouve frontal positions to the surveyed initial deposition of moraine 3. The displayed past positions are those with a resultant moraine exposure, relevant to the lichen transects and sampled trees.

The shape and location of the 1977 position matches the actual captured glacier front (Fig. 5.1.6), furthering the supported of this reconstruction. The glacier was in an episode of retreat from 1971-1922, with intermittent advances during the 1940s and in 1922-24. A 1964 overlay of calculated position and aerial photograph (Fig. 5.1.7) maintains the correct association during this time. The 1940sâ&#x20AC;&#x2122; advances were insignificant to the previous and post depositional retreats. The advance of the early 1920s with the subsequent retreat brought about the deposition of moraine 2â&#x20AC;&#x2122;s toe (Fig. 5.1.2). Before 1922 advances occurred from 1915. This position of the glacier front prior to the advance is not concurrent with the apparent form of moraine 3â&#x20AC;&#x2122;s profile (Fig. 5.1.3), suggesting an alternative initial deposition of this lateral moraine. The presumed toe of the moraine also fails to associate with past fluctuations. An

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Chapter 5 â&#x20AC;&#x201C; Results

inference towards a further down-valley toe location can be suggested, which was deposited previous to 1901.

Fig. 5.1.4. The overlaid 1995 glacier position onto a 1995 aerial photo. Photograph courtesy of Prof. S. Lane, Durham University.

Fig. 5.1.5. The overlaid 1988 glacier position onto a 1988 aerial photo. Photograph courtesy of Prof. S. Lane, Durham University.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Fig. 5.1.6. The overlaid 1977 glacier position onto a 1977 aerial photo. Photograph courtesy of Prof. S. Lane, Durham University.

Fig. 5.1.7. The overlaid 1964 glacier position onto a 1964 aerial photo. Photograph courtesy of Prof. S. Lane, Durham University.

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Chapter 5 – Results

Figure 5.1.8 relates the 3 moraine toe depositions with the fluctuation chronology. The 1901 position, beyond this study’s surveyed moraine 3 end, is clearly not the start of this moraine’s retreat phase. Deposition of moraine 3 appears to be from 1896, where a sharp contrast between the prior high magnitude advance and subsequent retreat exists. The observed non-conforming part of moraine 3’s profile might be a lateral deposition of the pre-1900 advances. The formation of moraine 2 is visible as the 1920s’ cumulative length change peak, as well as moraine 1 in the mid 1990s.

The retreat-advance-retreat ‘staggered’ recession is associated with initial lateral moraine deposition (Lowe & Walker, 1997). This can be seen in the length change data as the cause for moraine 1 and 2 toe depositions. Additionally, the potential deposition from the 1940s’ ‘stagger’ would have been overridden by the 1970-80s advances. The acclaimed 1972 observation of an “ice-core protruding through established lateral moraine” (Whalley, 1973) corresponds with the start of an advance episode.

The glacier fluctuation reconstruction is in strong agreement with the data constraints available of multi-temporal aerial photography and length change records. Assessment of the lichenometric and dendrochronological techniques can hereafter be applied. The locations of the lichen transects (Fig. 5.1.9) and sampled trees (Fig. 5.1.10) can be correlated to the glacier retreat and exposure of the moraine to colonisation.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Fig. 5.1.8. Length change data for Glacier de Tsidjiore Nouve, modified from VAW (2008). The points at which toe deposition occurred for moraines 1 (red), 2 (blue) and 3 (green) are highlighted; dashed line symbolises the oldest position related to the study’s moraine 3 ‘toe’ (1901 AD).

Fig. 5.1.9. Glacier de Tsidjiore Nouve foreland with lichen transects displayed; moraine and foreland gradient is apparent.

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Chapter 5 â&#x20AC;&#x201C; Results

Fig. 5.1.10. Glacier de Tsidjiore Nouve foreland with sampled trees displayed; moraine and foreland gradient is apparent.

5.2 Lichenometry

Measurements collected of lichen diameters have been assessed according to their accuracy and precision of an age estimate, relative to their altitudinal situation. The measurement data is viewable, with accompanied statistical calculations, in Appendix 2.

Within the assembled data, the single sample point transects (including the moraine toes and two locations at the top of moraine 3) contribute to the intra-sample point variations as well as relative age to exposure. They are not included in the intratransect relative altitude comparison (those of bottom to top of slope). On the other

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

hand, the two-point transects (occurring near the toe and where confined near the tops of the moraines) are included for this ‘black site’ to ‘green site’ review; although proximity of points to one another limits differences. The only point excluded for precision comparison was the toe of moraine 1, with an anomalous percentage variance of >175 %, which was influenced in part by fluvial activity and therefore limiting the sample supply. Moraine 3’s higher altitude transects which do not correctly correlate to the fluctuation chronology are also excluded for daterelated (i.e. growth rate) comparisons.

Growth rates are formulated from a believed colonisation period since the lichens ceased to exist, which when correlated to the fluctuation chronology is from 2002, giving a lag of 5 years. A linear growth period is assumed with every individual transect representing one age (year of exposure). Intra-moraine, bottom to top of transect, differences have been plotted for the 3 moraines (Fig. 5.2.1), providing an inter-moraine comparison of the ‘green’/‘black’ zone theory irrelevant to absolute altitude. A negative value denotes opposite, while positive denotes support for the theory. Moraine 1 shows strong initial negative values, to -0.026 mm/year, before a slight (<0.01 mm/yr) positive trend of values for the latter, thus higher altitude, transects. Moraine 2, which has more included transects, displays a dominant pattern of positive growth rate differences, more so for latter transects, with a 0.039 highest value for a middle transect. Values of predominantly >0.01 occur for moraine 3, both positive and negative. No significant association is visible between the distance along the moraine and positive/negative values. Overall, 77% of the foreland’s moraines have a positive value of ‘black’-‘green’ site growth rate differences.

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Chapter 5 – Results

Fig. 5.2.1. A ‘black’ and ‘green’ site comparison, expressed as the difference in calculated growth rate from transect top to bottom; shown for all separate moraines, along from moraine toe.

Further relationships have been calculated from sample point differences, at equal altitudes and exposure dates, comprising of 15 measurements. These have then been plotted against the altitude of the sample points. Moraine 1 (Fig. 5.2.2) shows a positive trend of percentage variance with altitude, significant to over 0.5 of the R2 correlation coefficient. A change of ca. 20 % per 10 metres increase in altitude is produced from the lowest percentage variance of 31.3 at 2232 m a.s.l. and the highest of 90.6 % at 2262 m. Comparatively, moraine 2 (Fig. 5.2.3) has a stronger positive correlation (R2 value of 0.8). The lowest variance of 16.8 % occurs at an altitude of 2211 m opposed to the highest variance of 155.8 % at 2349 m, at an increase of just ca. 7 % per 10 metres. The inter-moraine trend continues with moraine 3 (Fig. 5.2.4), which has a positive correlation of 0.65, and a percentage variance change of ca. 8 % per 10 metres with a lowest-highest variance change of 25.2-110.1 %. The strength of correlation ceases to increase further with moraine 3. The range of percentage

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

variance appears to increase with increased altitude, which can be shown on moraine 3 above 2280 m a.s.l. where it doubles from ca. 55 % to 110 %. All 3 moraines show a significant positive correlation, which generally increases on the older moraines from moraine 1; although the gradient of variance is contrary to this.

Fig. 5.2.2. Moraine 1: Plot of the correlation between altitude and intrasample point percentage variance; displayed with linear regression.

Fig. 5.2.3. Moraine 2: Plot of the correlation between altitude and intrasample point percentage variance; displayed with linear regression.

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Chapter 5 â&#x20AC;&#x201C; Results

Fig. 5.2.4. Moraine 3: Plot of the correlation between altitude and intrasample point percentage variance; displayed with linear regression.

Amalgamation of the data relative to absolute altitude can signify general, moraine non-specific, trends. Figure 5.2.5 shows a negative correlation between calculated growth rate and altitude. The strength of this linear correlation is below the significant R2 value of 0.5, and it is highly evident that between 2230 m and 2280 m, especially towards the latter, increased variability of growth rate occurs. These apparent anomalies are a result of the fluctuation chronology method; the 2-year fluctuation ignored the 1-year variation of the glacier front. The youngest moraine (1) of small lichens is susceptible to this.

For two transects on moraine 1, a re-evaluation of the reconstruction at a 1-year scale highlighted false exposure dates, which have been re-correlated with changed growth rate implications.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Fig. 5.2.5. Collective sample point growth rate data plotted against absolute altitude; displayed with linear regression and correlation coefficient.

The corrected plot can be seen as figure 5.2.6; a much improved linear correlation is evident as 0.76 from 0.33. A sharp reduction in growth rate is found with the higher altitudes, which could be interpreted as a threshold. Acknowledgement of this ca. 2290 m a.s.l. â&#x20AC;&#x2DC;thresholdâ&#x20AC;&#x2122; presents a further increased correlation to an R2 value of 0.92.

Fig. 5.2.6. Corrected sample point growth rate data against altitude (Fig. 5.2.5); displayed with linear (dark grey, dashed) and polynomial (black) regressions, along with associated line equation and correlation coefficient.

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Chapter 5 â&#x20AC;&#x201C; Results

An alternative evaluation of the lichenometric measurements within this glacier foreland is the recognition of sample point variance (Fig. 5.2.7). Although there are fairly high fluctuations the polynomial trend, from a moderately stationary low variance (<40 %) to escalating variance with increased altitude, shows a significant correlation. Apparent from the 10 m average altitude increase are two points of a variance rise, after ca. 2230 m and then more so after ca. 2290 m. The increased variance seems exponential, rising to over 100 percent above 2290 m.a.s.l; maximum variance being 120.5 % at 2309 m.

Fig. 5.2.7. Sample point percentage variance against altitude; displayed with 10 m altitude average (dark grey) and polynomial regression (black).

5.3 Dendrochronology

European Larch have been cored and measured on the 2 moraines inhabiting trees; the older moraines 2 and 3. The spatial positions of these sampled trees have been

- 45 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

recorded on a vertical absolute altitude scale and a horizontal scale relative to the fluctuation chronology. The collected data are viewable in Appendix 3. Those trees which could not be correlated to an exposure date have been excluded from the agerelevant analysis; these are those towards the top of moraine 3 and the highest of assumed moraine 2.

The treeline was documented for this part of the valley, and the highest outpost positions existed across the top the Tsidjiore Nouve foreland. This was done for the relevant L. decidua species; a few P. cembra were observed at higher altitudes. The outpost treeline was recorded in 4 locations (Appendix 4), with a mean average of 2402 m a.s.l. The highest tree elevation was just south of the foreland at 2420 m a.s.l.

Fig. 5.3.1. Moraine 2: Correlative plot of sampled tree altitude against the age difference between its ring count and estimated exposure age, for each aspect of the moraine; displayed with linear regression and correlation coefficient.

An intra-moraine study is achieved from distinguishing the aspect within the moraine (i.e. which side the tree is growing on). Moraine 2 (Fig. 5.3.2) shows relatively non-

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R. S. Jones, 2008

Chapter 5 â&#x20AC;&#x201C; Results

significant trends of the age difference with altitude. The proximal side of the moraine has a much stronger correlation, with a positive relationship between the two variables. The distal slope denotes a negative correlation; however with highly insignificant strength, much like the crest relationship. More samples are found on the proximal slopes.

Collectively there is an R2 output value of just 0.18 for a positive trend. For moraine 3, correlation is improved for every aspect (Fig. 5.3.2). A positive relationship is apparent for the proximal and distal sides as well as the moraine crest. Collectively, the R2 value is 0.29. The distal south side has a greatly increase correlation relative to the crest on moraine 3. The proximal north side still has the dominant strength over the other aspects for this positive altitude-age difference relationship.

Fig. 5.3.2. Moraine 3: Correlative plot of sampled tree altitude against the age difference between its ring count and estimated exposure age, for each aspect of the moraine; displayed with linear regression and correlation coefficient.

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

The other measurements collected were of trunk girth and the treeâ&#x20AC;&#x2122;s height. An intermoraine comparison of the relationship of these variables with height has been made (Fig. 5.3.3). A girth-height ratio rises as girth increases relative to height. The correlation of this trend against altitude is statistical significant for both moraines; collectively producing R2 of 0.59. Moraine 2â&#x20AC;&#x2122;s positive relationship is not quite as strong as moraine 3, but the gradient of the regression is higher with higher altitude tree locations. Low ratio and altitude clustering of samples is apparent relative to the higher altitudes.

Fig. 5.3.3. The increase of girth in relation to height with increased altitude, for the two tree-occupied moraines; displayed with linear regression and correlation coefficient.

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R. S. Jones, 2008

Chapter 6 – Discussion

6. Discussion

6.1 Fluctuation chronology

The use of Glacier de Tsidjiore Nouve’s retreat data (VAW, 2008) combined with multi-temporal aerial photography has produced a fluctuation chronology applicable to the foreland’s surveyed moraines. Previous literature has documented some of the fluctuations identified from the retreat data and past glacier-front reconstructions. The advance of the 1970-80s was observed by Small et al. (1984), with the displacement of a moraine from the initial advance being noted in 1972 (Whalley, 1973). This advance formed moraine 1, the most recent moraine, which deposited its ‘dump’ toe after 1995 when a continuous phase of retreat began exposure of the moraine. Moraine 2 is associated with the early 1920s ‘staggered’ retreat, beginning dump deposition and exposure in 1926.

Moraine 3 brings complications. The assumed toe appears false, and is likely the result of anthropogenic infrastructure developments; an off-road track and footpath. The retreat data solely indicates dumping of the moraine after the Little Ice Age, in 1896, a point of sharp glacier recession. The true toe of moraine 3 would therefore lie further down the valley sides. The anomalous correlation with the fluctuation chronology found higher up moraine 3 could be explained by the “fossil” feature character of the Tsidjiore Nouve foreland boundary (Small, 1983). Röthlisberger & Schneebeli (1979) claimed that the “moraine walls” were built up over the past 3,500

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

years of advances. Later supra-glacial overflow onto the fossil moraine occurred (Small et al., 1984), providing a subsequent colonisation period.

6.2 Lichenometry

Jomelli et al. (2007) proposed three criteria necessary for lichenometric assessment, two of which appear susceptible to an altitudinal gradient. Both the accuracy, derived from growth rate calculations, and precision of date estimations, observed from the variance of sample data, have been affected.

The mean of largest lichen diameters formulated with colonisation lag and age since exposure has provided growth rates for each altitude sample point. Linear growth is assumed. However, the inclusion of multi-age inter-moraine sample points to a collective plot avoids potential minor curvilinear growth patterns. Additionally, the phase of linear ‘great period’ growth (Beschel, 1950) is often found to extend beyond the ca. 100-year age found in this study (Innes, 1985a). The linear-curvilinear stages of growth are recognised as being size- rather than age-dependent (Innes, 1985a), which is an aspect shown to be effected by altitude by this study.

The theory of increased preferential growth at the base of moraine slopes (Matthews, 1977; Haines-Young, 1983; Innes, 1986), with respect to intra-moraine relative altitudinal difference, has been reviewed. 77% of the moraine transects supported this theory, with the largest top-bottom growth rate gradients occurring in favour. A decreased growth rate at the top/crest (‘black site’) of the moraine is associated with

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R. S. Jones, 2008

Chapter 6 â&#x20AC;&#x201C; Discussion

severe environmental conditions (Innes, 1986). The trend could be potentially projected down-valley, possibly with moraine 3, to see whether it continues for lower altitudes. Up-valley, along-moraine relationships are not a measure of absolute altitude, but the support for the theory appears more coherent at higher altitude where the gradient is stronger.

Variance of the sample data signifies the precision of potential results. Although the sample points represent small areas, which have been shown to have increased variation (Innes, 1984), this sampling was standard for each location of data collection. It is documented that â&#x20AC;&#x2DC;black zonesâ&#x20AC;&#x2122;, an indication of high relative altitude, have smaller variances due to the more severe conditions limiting growth variations (Innes, 1986). The evidence provided in this study shows a significant positive correlation between absolute altitude and percentage variance. This is at odds with harshening conditions as a growth limiter. A stronger gradient of variance is found within moraine 1, which is likely to represent its location as the highest altitude moraine, probably coupled with the influence on early growth as the moraine hosts the most recent establishment. Incorporation of all moraines shows a fluctuation of variance when plotted, which could represent microenvironments differing along the moraines (Innes, 1985a). The collective foreland altitude-growth rate relationship has a significant negative correlation, as a decreased growth rate with increased altitude. The methodological approach coupled with the combined growth rate-altitude data plot excludes other variables as possible factors. A threshold is apparent within the relationship, which is reached after the gradual decrease with altitude (from ca. 2230 m), indicating a large reduction in growth rate at 2280-2290 m a.s.l. This is

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

comparable to the noticeable rise in percentage variance, also transpiring at ca. 2285 m.

The reasons for an increase in variance and decrease in growth rate relative to altitude may be associated with uncontrolled and unquantified altitudinal variables. Included within these are moisture availability (Innes, 1985b), temperature (Kershaw, 1983), light intensity (Gauslaa, 1984), snowcover (Sancho et al., 2001), and wind exposure (Benedict, 1967) with related exposition (Pentecost, 1979). Data is available for the factors of temperature, snowcover and frost, for nearby Valais stations (see Table 6.2.1). Days of frost and snowcover provide a more direct and noteworthy indication towards altitudinal effects. For every 100 m increased altitude (possible within a foreland), ca. 15 more days of frost and ca. 18 more days of snowcover could occur per year. Winter snowcover has a significant mean increase, with nearly 3 days more snowcover a month per 100 metres in elevation.

Most of the ecological variables are considered to be effective on larger than intraforeland scales (Innes, 1985a). Micro-environment variations have been associated with snowcover, with a mean snow-free growing season of 95 days (Sancho et al., 2001). Such a relationship is regarded as being relevant to ‘black’-‘green’ site differences (Innes, 1986); although Innes (1986) recognises snowcover as being preferential to ‘green’ zones as a buffer. Alternatively, a biological factor of increased growth rate at lower altitudes and ‘green’ sites is competition (Innes, 1986), due to a requirement of domination for survival.

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R. S. Jones, 2008

Chapter 6 – Discussion

Table 6.2.1. Available data of altitude-relevant climatic variables. Temperature (deg. C) Altitude (m a.s.l.) Annual

Winter (DJF)

Summer (JJA)

Station

Valley

1825 2472 Difference Gradient (/100 m)

3.5 -1.3 4.8 0.74

-3.0 -7.5 4.5 0.69

10.4 5.7 4.7 0.73

Evolène-Villaz Gd-St-Bernard

Val D'Herens Gd-St-Bernard

Frost (days) Altitude (m a.s.l.)

Annual

Winter (DJF)

Summer (JJA)

Station

Valley

1825 2472 Difference Gradient (/100 m)

154.7 249.1 94.4 14.59

26.0 29.9 3.9 0.60

0.8 7.2 6.4 0.99

Evolène-Villaz ** Gd-St-Bernard

Val D'Herens Gd-St-Bernard

Annual

Winter (DJF)

Summer (JJA)

Station

Valley

42.5 161.7 119.2 18.42

7.4 25.6 18.2 2.81

0.0 0.9 0.9 0.14

Evolène-Villaz ** Gd-St-Bernard *

Val D'Herens Gd-St-Bernard

Snowcover (days) Altitude (m a.s.l.) 1825 2472 Difference Gradient (/100 m)

Climatic variables relevant to altitude; it is acknowledged that aspect amongst others has influence. Values are displayed for nearby Valais region stations, at altitudes above and below that of Tsidjiore Nouve foreland. The values are mean climatic values of 1961-90; except: *from 1964 and **from 1986. The difference between the two sites and the gradient of change per 100 metres is calculated. Data is courtesy of MeteoSwiss.

6.2.1 Modelling growth rate with altitude – Implications

The dating technique is based on the principle that a growth rate for the sampled lichens is known, whether this is obtained by direct or indirect methods (cf. Innes, 1985a). When a temporal aspect is applied to the relationship between growth rate and altitude, large differentiations arise on an intra-foreland scale (Fig. 6.2.1.2).

The growth curve generated by Gurnell & Clarke (1987) was based on tombstones at an unspecified altitude lower than the Tsidjiore Nouve foreland (Fig. 6.2.1.1). The modelled growth is significantly different to Tsidjiore Nouve, making it incompatible

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

for use at this site. The intra-foreland differences are quantified as 20, 13 and 6 mm after 50 years of growth, for the low, higher and high post-threshold elevations respectively (in Fig. 6.2.1.2). An increased age

will

divergence

also

provide

increased

growth

rate

between

altitudes. If curvilinear growth was plotted, divergence would still occur until the plateau is reached, which is likely to be delayed for the higher altitudes. Failed acknowledgment of this intraforeland altitudinal effect, when using an

Fig. 6.2.1.1. Lichen growth curve for Val d’Herens, Valais, Switzerland; based on tombstone measurements (Modified from Gurnell & Clarke, 1987).

impractical growth curve and assumed standard growth rate, would result in highly inaccurate substrate dates.

Fig. 6.2.1.2. Gurnell & Clarke (1987) Val d’Herens linear growth rate of 0.53 mm/yr against intra-foreland growth ‘curves’ for three different altitudes; extrapolations of growth rates formulated from the growth rate with altitude correlation (fig. 5.2.6): 2184 m, 0.4 mm/yr; 2271 m, 0.26 mm/yr; 2332 m, 0.12 mm/yr.

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R. S. Jones, 2008

Chapter 6 â&#x20AC;&#x201C; Discussion

6.3 Dendrochronology

The technique requires correct identification of a foreland ecesis period (Winchester & Harrison, 2000) and avoiding of false tree-rings (Fritts et al., 1991), in addition to the correct identification of an oldest representative tree (Luckman, 1986). One might expect the dating technique to be susceptible to a delayed lag of establishment and/or false tree-rings with increased environmental stress (Fritts et al., 1991; Block & Treter, 2001; Rammig et al., 2007). Tree growth is most sensitive with proximity to the treeline (Fritts, 1976; Innes, 1991), signifying the factor of altitude.

The difference between the substrate exposure age and the tree age (indicated by the ring count) is inclusive of the ecesis period and possible false tree-rings. Although the Tsidjiore Nouve foreland is adjacent to the treeline, no significant correlation was found associating an increased substrate-tree age difference and an increase in altitude. A possible source of age difference could also originate from an incorrectly dated substrate.

The glacier fluctuation chronology assumed that the exposure age (and/or time for establishment) was the same for each aspect, of proximal and distal sides as well as the moraine crest. Although the distal slopes become exposed during formation, this assumption is in accordance with the report that secondary deposition occurs on the distal slopes during the same year as proximal deposition at Tsidjiore Nouve (Small et al., 1984). The lack of a significant relationship for a substrate and tree age difference with the distal slopes supports this theory that there is equal ecesis. The

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

sample size for the distal slopes and the crest is limited, especially for moraine 2, and should be acknowledged. The crestsâ&#x20AC;&#x2122; low correlation with altitude could be due to the more stable and higher competitive position on the moraine for this light-loving species (Shiyatov, 1986), reducing the altitudinal effects; opposed to the idea that increased exposure would induce increased stress (Matthews, 1992).

An altitudinal effect is apparent on tree physiology. The high girth:height ratio is indicative of a decrease in tree height with altitude (Paulsen et al., 2000; Rammig et al., 2007), rather than girth which is representative of ring width, shown to decrease with altitude (Treter, 1984). Those factors associated with limiting growth height, but not a significant stress towards false tree-rings or prolonged ecesis, are temperature (KĂśrner & Paulsen, 2004), season length (Hadley & Smith, 1990), nutrient limitations (Brown & Higginbotham, 1986), or higher rates of nitrogen deposition and carbon dioxide fertilisation (Innes, 1991).

The implications for dendrochronology in respect of the effects of intra-foreland altitude and proximity to the treeline are limited. While age differences do vary, there is no significant trend relative to altitude. Difficulties may arise with the choice of a largest tree in obtaining the minimum substrate exposure age (Luckman, 1986). This study makes apparent the need for acknowledging growth physiology relative to altitude when sampling for an oldest tree.

The Tsidjiore Nouve foreland is situated in a mid- treeline ecotone (cf. KĂśrner & Paulsen, 2004). The recorded average treeline of ca. 2400 m a.s.l. is in keeping with that of the nearby Zermatt region of 2400-2500 m a.s.l. (Carnelli et al., 2004b);

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R. S. Jones, 2008

Chapter 6 – Discussion

however, the maximum elevation of 2420 m a.s.l. is over 100 m higher than that of nearby Arpette at 2300 m a.s.l. (Carnelli et al., 2004b). Within the Swiss Alps it is recognised that although L. decidua might be the dominant species for some low treelines, P. cembra is often the dominant species of a treeline, which occurs at a higher altitude (Körner & Paulsen, 2004).

6.4 Future work and improved research

Accepting the altitudinal effect found on lichen, a development of this study would be to examine down-valley of Tsidjiore Nouve for a possible extrapolation of growth rate and variance effects. The investigation could also be supported on a local level, with replication on the nearby forelands of Bas d’Arolla – Haut d’Arolla, as well as that of Glacier de Pièce at a higher altitude to Tsidjiore Nouve. Same altitude replication could potentially be carried out at other European Alps and global locations to identify a similar trend and apparent threshold. Variations of the relationships in relation to latitudinal position and hygric continentality (Gams, 1932) could be investigated. An inclusion of lichen size-frequency distributions (Innes, 1983, 1986) would assist in distinguishing between the effects on colonisation lag and growth rate. Further recognition of curvilinear growth would also be beneficial.

Date reproducibility is an important consideration to any lichenometric study (Locke et al., 1979). Future use of this dating technique should have standardised sampling with respect to ‘green sites’ (Innes, 1986), and with further documented support,

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

acknowledgement of sampling variance and altitude-influenced growth rate curves is essential.

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R. S. Jones, 2008

Chapter 7 – Conclusion

7. Conclusion

The investigation on the foreland of Tsidjiore Nouve in the Swiss Alps has involved a glacier fluctuation reconstruction which has aided in the assessment of lichenometry and dendrochronology with respect to altitude. A correlation between the fluctuation chronology and the surveyed sample data for the two techniques has formulated trends and variability associated with an altitudinal gradient. The strengths and inclinations of the relationships, in addition to the findings from the foreland surveillance and reconstruction, are concluded to be that: 

the three main moraines have been associated with an initial deposition date of 1995, 1923 and 1896, with a respective age of 12, 84 and 111 years; post LIA advances. Agreement does exist over the “fossil” outer moraine walls’ earlier Holocene date (Röthlisberger & Schneebeli, 1979; Small, 1983);



lichen establishment on the foreland occurs after a 5-year lag;



dendrochronological data is concurrent with the theory of distal slope secondary deposition (Small et al., 1984) and an equal proximal-distal slope ecesis period;



the intra-moraine ‘green’ zone (Matthews, 1977; Haines-Young, 1983) and ‘black’ zone (Innes, 1986) theory for preferential growth at basal moraine elevations is largely supported, and may have increased consistency with higher altitudes;



lichenometric variance of samples occurs with increased altitude of the foreland, indicated by inter-moraine analysis;

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The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale



growth rates of lichen are shown to decrease with altitude. The relationship provided an apparent threshold at ca. 2280-2290;



the Larix decidua outpost treeline reached 2420 m a.s.l., higher than others recorded in the Valais region;



altitudinal stress is not identified in effecting the ring-count or ecesis period with a proximity to the treeline;



tree physiology, in the form of girth and height, is affected by the altitudinal gradient; with inter-moraine support. Height decreases with increased altitude.

Implications for dendrochronology are limited, if growth physiology with altitude is acknowledged, but could be significant for lichenometry. The effects of intraforeland absolute altitude upon the reliability of a lichen-derived substrate age can provide highly inaccurate results. Further support is required at regional and global scales.

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R. S. Jones, 2008

References

Anderson, E., Harrison, S. and Passmore, D. G. (1998). Geomorphological mapping and morphostratigraphic relationships: Reconstructing the glacial history of the Macgilly-cuddy’s Reeks, south west Ireland. Society of Cartographers Bulletin, 30, p. 9-20.

Andrews, J. T. & Barnett, D. M. (1979). Holocene (Neoglacial) moraine and periglacial lake chronology, Barnes Ice Cap, North West Territories, Canada. Boreas, 8, p. 341-358.

Armstrong, R. A. (2002). The effect of rock surface aspect on growth, size structure and competition in the lichen Rhizocarpon geographicum. Environmental and Experimental Botany, 48, p. 187-194.

Armstrong,

(2004).

Lichens,

lichenometry

and

global

warming.

Microbiologist, September, p.32-35.

Avery, T. E. (1977). Interpretation of Aerial Photographs. Minneapolis: Burgess.

Belloni, S. (1973). Ricerche lichenometriche in Valfurva e nella Valle di Solda. Bolletino Comitato Glaciologico Italiano, 21, p. 19-33.

Benedict, J. B. (1967). Recent glacial history of an alpine area in the Colorado Front Range, USA. Establishing a lichen growth curve. Journal of Glaciology, 6, p. 817– 832.

Benedict, J. B. (1990). Lichen mortality due to late-lying snow: results of a transplant study. Arctic and Alpine Research, 22, p. 81–99.

- 61 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Benn, D. I. & Evans, D. J. A. (1998). Glaciers and Glaciation. London: Arnold.

Beschel, R. E. (1950). Flecten als altersmasstab Rezenter morainen. Zeitschrift für Gletscherkunde und Glazialgeologie, 1, p. 152–161.

Beschel, R. E. (1961). Dating rock surfaces by lichen growth and its application to glaciology and physiography (lichenometry). In: R.G.O. (Ed.), Geology of the Arctic. Toronto: University of Toronto Press, p. 1044–1062.

Beschel, R. E. (1973). Lichens as a measure of the age of recent moraines. Arctic and Alpine Research, 5(4), p. 303-309.

Blijenberg, H. (1998). Rolling stones. Triggering and frequency of hillslope debris flows in the Bachelard Valley, Southern French Alps. Universiteit Utrecht, Faculteit Ruimtelijke Wetenschappen, p. 223.

Block, J. & Treter, U. (2001). The limiting factors at the upper and lower forest limits in the mountain-woodland steppe of Northwest Mongolia. In: Dobbertin, K. M., Bräker O. U. (Eds.), International Conference Tree Rings and People. 250 Davos, 22–26 September 2001, Abstracts. Birmensdorf, Swiss Federal Research Institute WSL.

Bollschweiler, M., Stoffel, M. and Schneuwly, D. (2006). Assessing the SpatioTemporal Debris-Flow Activity on a Forested Cone using Tree-Ring Data. Disaster Mitigation of Debris Flows, Slope Failures and Landslides, 2(8), p. 597-604.

Boulton, G. S. & Eyles, N. (1979), Sedimentation by valley glaciers: a model and genetic classification. In: Schluchter, C. (Ed.), Proceedings of an INQUA symposium on genesis and lithology of Quaternary deposits, Zurich, 10-20 September 1978, Moraines and Varves: origin, genesis, classification. Rotterdam: A. A. Balkema, p. 11-23.

- 62 -

R. S. Jones, 2008

References

Boulton, G. S., Jones, A. S., Clayton, K. M., Kenning, M. J. (1977), A British icesheet model and patterns of glacial erosion and deposition in Britain. In: Shotton, F. W. (Ed.), British Quaternary Studies: Recent Advances. Oxford: The Clarendon Press, pp. 231-246.

Bradwell, T. & Armstrong, R. A. (2007). Growth rates of Rhizocarpon geographicum lichens: a review with new data from Iceland. Journal of Quaternary Science, 22(4), p. 311-320.

Bradwell, T., Dugmore, A. J. and Sugden, D. E. (2006). The Little Ice Age glacier maximum in Iceland and the North Atlantic Oscillation: evidence from Lambatungnajokull, southeast Iceland. Boreas, 35, p. 61-80.

Brook, E. J., Nesje, A., Lehman, S. T., Raisbeck, G. M. and Yiou, F. (1996). Cosmogenic nuclide exposure ages along a vertical transect in western Norwary: Implications for the height of the Fennoscandian ice sheet. Geology, 24, p. 207-210.

Brown, D. G., Lusch, D. P. and Duda, K. A. (1998). Supervised classification of types of glaciated landscapes using digital elevation data. Geomorphology, 21, p. 233-250.

Brown, K. & Higginbotham, K. O. (1986). Effects of carbon dioxide enrichment and nitrogen supply on growth of boreal tree seedlings. Tree Physiology, 92, p. 223-232.

Burga, C. A. (1999). Vegetation development on the glacier forefield Morteratsch (Switzerland). Applied Vegetation Science, 2, p. 17-24.

Burga, C. A., Frauenfelder, R., Ruffet, J., Hoelzle, M. and K채채b, A. (2004). Vegetation on Alpine rock glacier surfaces: a contribution to abundance and dynamics on extreme plant habitats. Flora - Morphology, Distribution, Functional Ecology of Plants, 199(6), p. 505-515.

- 63 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Carnelli, A. L., Theurillat, J-P. and Madella, M. (2004a). Phytolith types and typefrequencies in subalpine-alpine plant species of the European Alps. Review of Palaeobotany and Palynology, 129, p. 39-65.

Carnelli, A. L., Theurillat, J-P., Thinon, M., Vadi, G. and Talon, B. (2004b). Past uppermost tree limit in the Central European Alps (Switzerland) based on soil and soil charcoal. The Holocene, 14(3), p. 393-405.

Copenheaver, C. A, Pokorskib, E. A, Curriea, J. E. and Abramsc, M. D. (2006). Causation of false ring formation in Pinus banksiana: A comparison of age, canopy class, climate and growth rate. Forest Ecology and Management, 236(2-3), p. 348355.

Cook, E. R. & Kairiukstis, L. A. (1990). Methods of Dendrochronology: Applications in the Environmental Sciences. Dordrecht: Kluwer.

Cooley, D., Naveau, P. and Jomelli, V. (2006). A Bayesian Hierarchical Extreme Value Model for Lichenometry. Environmetrics, 17, p. 555-574.

Dowdeswell, J. A. (1986). Remote sensing of ice cap outlet glacier fluctuations on Nordaustlandet, Svalbard. Polar Research, 4, p. 25-32.

Ellis, J. M., Hamilton, T. D. and Calkin, P. E. (1981). Holocene glaciation of the Arrigetch Peaks, Brooks Range, Alaska. Arctic, 34, p. 158-168.

Espizua, L. E. (1986). Fluctuations of the Rio del Plomo glaciers. Geografiska Annaler (Series A), 68, p. 317-328.

Evans, D. J. A., Archer, S. and Wilson, D. J. H. (1999). A comparison of the lichenometric and Schmidt hammer dating techniques based on data from the proglacial areas of some Icelandic glaciers. Quaternary Science Reviews, 18, p. 1341.

- 64 -

R. S. Jones, 2008

References

Fahey, B. D. (1986). Weathering pit development in the Central Otago mountains of southern New Zealand. Arctic and Alpine Research, 18, p. 337-348.

Flint, R. F. (1971). Glacial and Quaternary Geology. New York: Wiley.

Follman, G. (1961). Estudios liquenometricos en los monumentos pre-historicos de la Isla de Pascua. Revista Universitaria – Anales de la Academia Chilena de Ciencias Naturales, 24, p. 149-154.

Ford, J. P. (1984). Mapping of glacial landforms from Seasat radar images. Quaternary Research, 22, p. 314-327.

Fritts, H. C. (1976). Tree rings and climate. London: Academic Press.

Fritts, H. C., Vaganov, E. A., Sviderskaya, I. V. and Shashkin, A. V. (1991). Climatic variation and tree-ring structure in conifers: empirical and mechanistic models of tree-ring width, number of cells, cell size, cell-wall thickness and wood density. Climate Research, 1, p. 97-116.

Gams, H. (1931). Die Miatische Begrenzung von Pflanzenarealen und die Verteilung der hygrischen Kontinentalitiit in den Alpen. Zeitschrift der Gesellschaft fur Erdkunde zu Berlin, p. 321-346.

Gams, H. (1932). Zur Geschichte der Moore der Kurischen Nehrung. und des Samlands. Schrift Physi-ökon Ges Königsberg. Preussen, 67(3), p. 74–87.

Gauslaa, Y. (1984). Heat Resistance and Energy Budget in Different Scandinavian Plants. Holarctic Ecology, 7(1), p. 5-78.

Gilbert, O. (2000). Lichens. London: Harper Collins.

Gurnell A. M. Clarke M. J. (1987). Glacio-fluvial Sediment Transfer: an Alpine Perspective. London: Wiley.

- 65 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Hadley, J. L. & Smith, W. K. (1987). Influence of krummholz mat microclimate on needle physiology and survival. Oecologia, 73, p. 82-90.

Haeberli, W., King, L. and Flotron, A. (1979). Surface movement and lichen-cover studies at the active rock glacier near the Grubengletscher, Wallis, Swiss Alps. Arctic and Alpine Research, 11, p. 421-441.

Haefeli,

(1955-56).

Gletscherschwankung

und

Gletscherbewegung.

Schweizerische Bauzeitung, Jahrg. 73, Ht. 42. p. 626-631; Ht. 43, p. 693-697; Jahrg. 74, Ht. 44, p. 667-669.

Haines-Young, R. H. (1983). Size variation of Rhizocarpon on moraine slopes in southern Norway. Arctic and Alpine Research, 15, p. 295–305.

Hale, M. E. Jr. (1967), The Biology of Lichens. London: Arnold.

Hubbard, B. (1997). Modelling climate, topography and palaeoglacier fluctuations in the Chilean Andes. Earth Surface Processes and Landforms, 22, p. 77-92.

Hubbard, B. & Glasser, N. (2005). Field techniques in glaciology and glacial geomorphology. Chichester: Wiley.

Innes, J. L. (1983). Size frequency distributions as a lichenometric technique: an assessment. Arctic and Alpine Research, 15, p. 285–294.

Innes, J. L. (1984). The optimal sample size in lichenometric studies. Arctic and Alpine Research, 16, p. 233–244.

Innes, J. L. (1985a). Lichenometry. Progress in Physical Geography, 9, p. 187–254.

Innes, J. L. (1985b). Moisture Availability and Lichen Growth: The Effects of Snow Cover and Streams on Lichenometric Measurements. Arctic and Alpine Research, 17, p. 417-424.

- 66 -

R. S. Jones, 2008

References

Innes, J. L. (1986). Influence of sampling design on lichen size–frequency distributions and its effects on derived lichenometric indices. Arctic and Alpine Research, 18, p. 201–208.

Innes, J. L. (1991). High-altitude and high-latitude tree-growth in relation to past, present and future global climate change. Holocene, 1, p. 168- 173.

Jacobsen, F. M. & Theakstone, W. H. (1997). Monitoring glacier changes using a global positioning system in differential mode. Annals of Glaciology, 24, p. 314-319.

Jochimsen, M. (1973). Does the size of lichen thalli really constitute a valid measure for dating glacial deposits? Arctic and Alpine Research, 5(4), p. 417-424.

Jomelli, V., Grancher, D., Naveau, P., Cooley, D. and Brunstein, D. (2007). Assessment study of lichenometric methods for dating surfaces. Geomorphology, 86, p. 131-143.

Johnson, O. & More, D. (2004). Tree Guide. London: HarperCollins.

Karlen, W. & Black, J. (2002). Estimates of lichen growth-rate in northern Sweden. Geografiska Annaler, 84A, p. 225–232.

Kershaw, K. A. (1983). The Thermal Operating-Environment of a Lichen. The Lichenologist, 15, p. 191-207.

Körner, Ch. (1998). A re-assessment of high elevation treeline positions and their explanation. Oecologia, 115, p. 445-459.

Körner, Ch. & Paulsen, J. (2004). A world-wide study of high altitude treeline temperatures. Journal of Biogeography, 31, p. 713-732.

Lang, A., Moya, J., Corominas, J., Schrott, L. and Dikau, R. (1999). Classic and new dating methods for assessing the temporal occurrence of mass movements. Geomorphology, 30, p. 33-52.

- 67 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Li, M.H., Yang, J. and KrĂ¤uchi, N. (2003). Growth responses of Picea abies and Larix deciduas to elevation in subalpine areas of Tyrol, Austria. Canadian Journal of Forest Research, 33(4), p. 653-662.

Li, Z., Sun, W. and Zeng, Q. (1998). Measurements of glacier variation in the Tibetan Plateau using Landsat data. Remote Sensing of Environment, 63, p. 258-264.

Lock[e], W. W. III, Andrews, J. T., Webber, P. J. (1979). A manual for lichenometry. British Geomorphological Research Group Technical Bulletin, 26, p. 47. Lowe, J. J. & Walker, M. J. C. (1997). Reconstructing Quaternary environments (2nd Ed.). Harlow: Longman.

Lowell, T. V., Schoenenberger, K., Dedens, J., Denton, G., Smith, C., Black, J. and Hendy, C. (2005). Rhizocarpon calibration curve for the Aoraki/Mount Cook area of New Zealand. Journal of Quaternary Science, 20, p. 313-325.

Luckman, B. H. (1977). Lichenometric dating of Holocene moraines at Mont Edith Cavell, Jasper, Alberta. Canadian Journal of Earth Sciences, 14, p. 1809-1822.

Luckman, B. H. (1986). Reconstruction of Little Ice Age events in the Canadian Rocky Mountains. Geographie Physique et Quaternaire, 40, 17-28.

Macklin, M. G., Rumsby, B. T. and Heap, T. (1992). Flood alleviation and entrenchment: Holocene valley floor development and transformation in the British Uplands. Geological Society of America Bulletin, 104, p. 631-643.

Martinelli, N. (2004). Climate from dendrochronology: latest developments and results. Global and Planetary Change, 40(1-2), p. 129-139.

Matthews, J. A. (1974). Families of lichenometric dating curves from the Storbreen gletschervorfeld, Jotunheimen, Norway. Norsk Geografisk Tidskrift, 28, p. 215â&#x20AC;&#x201C;235.

- 68 -

R. S. Jones, 2008

References

Matthews, J. A. (1975). Experiments on the reproducibility and reliability on lichenometric dates, Storbreen gletshervorfeld, Jotunheimen, Norway. Norsk Geografisk Tidskrift, 31, p. 129–136.

Matthews, J. A. (1977). Glacier and climatic variations inferred from tree-growth variations over the last 250 years, central southern Norway. Boreas, 6, p. 1-24.

Matthews, J. A. (1992). The ecology of recently-deglaciated terrain. Cambridge: CUP.

Matthews, J. A. (2005). ‘Little Ice Age’ glacier variations in Jotunheimen, southern Norway: a study in regionally controlled lichenometric dating of recessional moraines with implications for climate change and lichen growth rates. The Holocene, 15, p. 1-19.

McCarroll, D. (1994). A new approach to lichenometry: dating single-age and diachronous surfaces. The Holocene, 22, p. 383–396.

Moreau, M., Laffly, D., Joly, D. and Brossard, T. (2005). Analysis of plant colonization on an arctic moraine since the end of the Little Ice Age using remotely sensed data and a Bayesian approach. Remote Sensing of Environment, 99, p. 244253.

Mori, A., Osono, T., Iwasaki, S., Uchida, M., and Kanda, H. (2006). Initial recruitment and establishment of vascular plants in relation to topographical variation in microsite conditions on a recently-deglaciated moraine on Ellesmere Island, high arctic Canada. Polar Bioscience, 19, p.85-95.

Naveau, P., Nogaja, M., Ammann, C., Yiou, P., Cooley, D., Jomelli, V. (2005). Statistical methods for the analysis of Geophysical extreme events. Comptes Rendus de l'Académie des Sciences, Géosciences, 337, p. 1013–1022.

- 69 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Nikonov, A. A. & Shebalina, T. Yu. (1979). Lichenometry and earthquake age determination in central Asia. Nature, 280(23), p. 675-677.

Norton, D. A. (1983). A dendroclimatic analysis of three indigenous species, South Island, New Zealand. Ph.D. Dissertation, University of Canterbury, New Zealand.

Nyberg R. (1985). Debris flows and slush avalanches in northern Swedish Lappland. Distribution

and

geomorphological

significance.

Meddlanden

fran

Lunds

Universitets Geografiska Institution, 97.

Oâ&#x20AC;&#x2122;Neal, M. (2006). The effects of slope degradation on lichenometric dating of Little Ice Age moraines. Quaternary Geochronology, 1, p. 121-128.

Oâ&#x20AC;&#x2122;Neal, M. & Schoenenberger, K. (2003). A Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon, USA. Quaternary Research, 60, p. 233-241.

Orombelli, G. & Porter, S. C. (1983). Lichen growth curves for the southern flank of the Mont Blanc Massif, Western Italian Alps. Arctic and Alpine Research, 15(2), p. 193-200.

Osborn, G. D. (1978). Fabric and origin of lateral moraines, Bethartoli Glacier, Garhwal Himalaya, India. Journal of Glaciology, 20(84), p. 547-553.

Osborn, G. D. (1986). Lateral-moraine stratigraphy and neoglacial history of Bugaboo Glacier, British Columbia. Quaternary Research, 46(2), p. 171-178.

Osborn, G. D., Robinson, B. J. and Luckman, B. H. (2001), Holocene and latest Pleistocene fluctuations of Stutfield Glacier, Canadian Rockies. Canadian Journal of Earth Sciences, 38(8), p. 1141-1155.

Osborn, G. D. & Taylor, J. (1975). Lichenometry on calcareous substrates in the Canadian Rockies. Quaternary Research, 5, p. 111-120.

- 70 -

R. S. Jones, 2008

References

Paulsen, J., Weber, U. M. and KĂśrner, Ch. (2000), Tree growth near treeline: Abrupt or gradual reduction with altitude? Arctic, Antarctic, and Alpine Research, 32(1), p. 14-20.

Pech, P., Jomelli, V., Baumgart-Kotarba, M., Bravard, J. P., Chardon, M., Jacob, N., Kedzia, S., Kotarba, A., Raczkowska, Z. and Tsao, C. (2003). A lichenometric growth curve in the French Alps: Ailefroide and Veneon valleys; Massif des Ecrins. Geodinamica Acta, 16, p. 187-193.

Pelfini, M., Bozzoni, M. and Carton, A. (2005). The contribution of dendroglaciology for the reconstruction of historical fluctuations of the Madaccio Glacier (BZ, Italy) and the definition of its scientific attribute and ecological value. Geophysical Research Abstracts, 7.

Pentecost, A. (1979). Aspect and slope preferences in a saxicolous lichen community. Lichenologist, 11, p. 81â&#x20AC;&#x201C;83.

Pilcher, J. R. (1990). Primary Data. In: Cook, E. R. & Kairiukstis, L. A., Methods of Dendrochronology: Applications in the Environmental Sciences. Dordrecht: Kluwer, p. 23-96.

Pilcher, J. R. (1991), Radiocarbon dating for the Quaternary scientist. In: Lowe, J. J. (Ed.), Radiocarbon Dating: recent applications and future potential. Quaternary Proceedings no. 1, Chichester: Wiley, p. 27-33.

Pilcher, J. R., Baillie, M. G. L., Schmidt, B. and Becker, B. (1984). A 7272-year European tree-ring chronology. Nature, 312, p. 150-152.

Porter, S. C. (1975). Weathering rinds as a relative-age criterion: Application to subdivision of glacial deposits in the Cascade Range. Geology, 3, p. 101-104.

Porter, S. C. (1981). Lichenometric studies in the Cascade range of Washington: Establishment of Rhizocarpon geographicum growth curves at Mount Rainer. Arctic and Alpine Research, 13(1), p. 11-23.

- 71 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Porter, S. C. & Orombelli, G. (1981). Alpine rockfall hazards. American Scientist, 69. p. 67-75.

Proctor, M. C. F. (1983). Sizes and growth-rates of thalli of the lichen Rhizocarpon geographicum on the moraines of the Glacier de Valsorey, Valais, Switzerland. Lichenologist, 15, p. 249-261.

Rammig, A., Bebi, P., Bugmann, H. and Fahse, L. (2007). Adapting a growth equation to model tree regeneration in mountain forests. European Journal of Forest Research, 126(1), p. 49-57.

Richards, B. W. M. (2000). Luminescence dating of Quaternary sediments in the Himalayas and High Asia: A practical guide to its use and limitations for constraining the timing of glaciation. Quaternary International, 65/66, p. 49-61.

RĂśthlisberger, F. & Schneebeli, W. (1979). Genesis of lateral moraine complexes, demonstrated by fossil soils and trunks: indicators of postglacial climatic fluctuations. In: Schluchter, C. (Ed.), Moraines and Varves. Balkema: Rotterdam, p. 387-419.

Runemark, H. (1956). Studies in Rhizocarpon, I. Taxonomy of the yellow species in Europe. Opera Botanica, 2(1), p. 1-152.

Sancho, L. G., Palacios, D., Marcos, J. de, and Valladares, F. (2001). Geomorphological significance of lichen colonization in a present snow hollow: Hoya del Cuchillar de las Navajas, Sierra de Gredos (Spain). Catena, 43, p. 323-340.

Selby, M. J. (1980). A rock mass strength classification for geomorphological purposes: With tests from Antarctica and New Zealand. Zeitschrift fĂźr Geomorphologie, 24, p. 31-51.

- 72 -

R. S. Jones, 2008

References

Shakesby, R. A., Dawson, A. G. and Matthews, J. A. (1987). Rock glaciers, protalus ramparts and related phenomena, Rodane, Norway: a continuum of large-scale talusderived landforms. Boreas, 16, p. 305-317.

Shiyatov, S. G. (1986). Dendrochronology in the Upper Tree Line in the Urals. Moscow: Nauka Publishing House.

Small, R. J. (1983). Lateral moraines of Glacier de Tsidjiore Nouve: Form, development, and implications. Journal of Glaciology, 29(102), p. 250-259.

Small, R. J., Beecroft, I. R. and Stirling, D. M. (1984). Rates of deposition on lateral moraine embankments, Glacier de Tsidjiore Nouve, Valais, Switzerland. Journal of Glaciology, 30(106), p. 275-281.

Spence, J. R. & Mahaney, W. C. (1988). Growth and ecology of Rhizocarpon section Rhizocarpon on Mount Kenya, East Africa. Arctic and Alpine Research, 20, p. 237242.

Stevens, G.C. & Fox, J.F. (1991). The causes of treeline. Annual Review of Ecology and Systematics, 22, p. 177â&#x20AC;&#x201C;191.

Stokes, M. & Smiley, T. L. (1996). An introduction to tree-ring dating. Tuscon: University of Arizona Press.

Swiss Glacier Monitoring (2008). Glacier length variations in the year 2007 [Online image],

SCNAT/VAW.

Available

from:

<http://glaciology.ethz.ch/messnetz/index.html> [Accessed 20/02/08].

SwissTopo (2004). Arolla, 1:50,000. Carte Nationale De La Suisse.

Treter,

(1984).

Die

Baumgrenzen

Skandinaviens.

Okologische

und

dendroklimatische Untersuchungen. Wiesbaden: Franz Steiner Verlag. VAW (2008). Length variation measurements between 1880 and 2007. Swiss Glacier Monitoring Network, ETH ZĂźrich.

- 73 -

The effect of altitude on lichenometry and dendrochronology at an intra-foreland scale

Webber, P. J. & Andrews, J. T. (1973). Lichenometry: A commentary. Arctic and Alpine Research, 5(4), p. 295-302.

Whalley, W. B. (1973). An exposure of ice on the distal side of a lateral moraine. Journal of Glaciology, 12(65), p.327-329.

Whalley, W. B. (1974). Rock glaciers & their formation: as part of a glacial debristransport system. Reading: Department of Geography, University of Reading.

Wimmer, R. & Vetter, R. E. (Eds.). (1999). Tree-ring analysis: Biological, methodological and environmental aspects. Wallingford: CABI.

Winchester, V. (1989). An evaluation of lichenometry: with field studies in Lappland, Britain and the Western Alps. D. Phil. Thesis, Faculty of Anthropology and Geography, University of Oxford.

Winchester, V. & Harrison, S. (1994). A development of the lichenometric method applied to the dating of glacially influenced debris flows in Southern Chile. Earth Surface Processes and Landforms, 19, p. 137-151.

Winchester, V. & Harrison, S. (1996). Recent oscillations of the San Quintin and San Rafael Glaciers, Patagonian Chile. Geografiska Annaler, 78A, p. 35-49.

Winchester, V. & Harrison, S. (2000). Dendrochronology and lichenometry: colonization, growth rates of geomorphological events on the east side of the North Patagonian Icefield, Chile. Geomorphology, 34, p. 181-194.

Winkler, S. (2003). A new interpretation of the date of the â&#x20AC;&#x2DC;Little Ice Ageâ&#x20AC;&#x2122; glacier maximum at Svartisen and Okstindan, northern Norway. The Holocene, 13, p. 83-95.

Worsley, P. (1990a). Lichenometry. In: Goudie, A. S. (Ed.), Geomorphological Techniques. London: Unwin Hyman, p. 422-428.

- 74 -

R. S. Jones, 2008

References

Worsley, P. (1990b). Tree-ring dating (dendrochronology). In: Goudie, A. S. (Ed.), Geomorphological Techniques. London: Unwin Hyman, p. 415-421.

Yingkui, L., Gengian, L. and Zhijiu, C. (2001). Longitudinal variations in crosssection morphology along a glacial valley: A case-study from the Tien Shan, China. Journal of Glaciology, 47, p. 243-250.

- 75 -

Appendices

- 76 -

Appendix 1 â&#x20AC;&#x201C; Glacier de Tsidjiore Nouve fluctuation data

Length variation measurements between 1880 and 2007 (VAW, 2008) Reference Year

Survey Year

Length Change (m)

Cum. Length Change (m)

Per 2 Years

Length Change

1880

1882

150

1882-1880

323

1882

1885

173

323

1886-1882

193

1889-1886

100

1893-1891

202

1895-1893

1897-1895

-68

1899-1897

-92

1901-1899

-132

1904-1901

-32

1906-1904

-74

1908-1906

-34

1910-1908

-21

1912-1910

-23

1914-1912

-22

1916-1914

1918-1916

1920-1918

1922-1920

-4

1924-1922

1926-1924

-27

1928-1926

-18

1930-1928

-36

1932-1930

-83

1885

1886

343

1886

1887

393

1888

1889

443

1891

1892

100

543

1892

1893

102

645

1893

1894

719

1894

1895

744

1895

1896

749

1896

1897

-73

676

1897

1898

-49

627

1898

1899

-43

584

1899

1900

-63

521

1900

1901

-69

452

1901

1902

-11

441

1902

1904

-21

420

1904

1905

-47

373

1905

1906

-27

346

1906

1907

-22

324

1907

1908

-12

312

1908

1909

-4

308

1909

1910

-17

291

1910

1911

-20

271

1911

1912

-3

268

1912

1913

-2

266

1913

1914

-20

246

1914

1915

268

1915

1916

293

1916

1917

311

1917

1918

331

1918

1919

351

1919

1920

366

1920

1921

372

1921

1922

-10

362

1922

1923

375

1923

1924

-6

369

1924

1925

-4

365

1925

1926

-23

342

1926

1927

-14

328

1927

1928

-4

324

1928

1929

-26

298

1929

1930

-10

288

1930

1931

-22

266

1931

1932

-61

205

- 77 -

1932

1933

-35

170

1933

1934

-44

126

1934

1935

-19

107

1935

1936

-9

1936

1939

-42

1939

1940

-24

1940

1941

1942

-26

1942

1943

1945

-26

-5

1945

1946

1947

1948

1949

-23

-5

1949

1950

-3

-8

1950

1951

-39

-47

1951

1952

-13

-60

1952

1953

-15

-75

1953

1954

-4

-79

1954

1955

-1

-80

1955

1956

-6

-86

1956

1957

-9

-95

1957

1958

-12

-107

1958

1959

-4

-111

1959

1960

-6

-117

1960

1961

-3

-120

1961

1962

-4

-124

1962

1963

-20

-144

1963

1964

-6

-150

1964

1967

-14

-164

1967

1968

-6

-170

1968

1969

-2

-172

1969

1970

-2

-174

1970

1971

-4

-178

1971

1972

-167

1972

1973

-158

1973

1974

-150

1974

1975

-137

1975

1976

-127

1976

1977

-111

1977

1978

-106

1978

1979

-96

1979

1980

-85

1980

1981

-57

1981

1982

-32

1982

1983

1984

1985

1986

1987

1988

1989

- 78 -

1934-1932

-79

1936-1934

-28

1940-1936

-66

1942-1940

-26

1945-1942

-11

1947-1945

1949-1947

-20

1951-1949

-42

1953-1951

-28

1955-1953

-5

1957-1955

-15

1959-1957

-16

1961-1959

-9

1963-1961

-24

1967-1963

-20

1969-1967

-8

1971-1969

-6

1973-1971

1975-1973

1977-1975

1979-1977

1981-1979

1983-1981

1985-1983

1987-1985

1989-1987

1989

1990

1991

-4

1991

1992

-8

1992

1993

-6

1993

1994

1995

1996

-1

1996

1997

-108

-18

1997

1998

-13

-31

1998

1999

-21

-52

1999

2000

-17

-69

2000

2001

-12

-81

2001

2002

-52

-133

2002

2003

-33

-166

2003

2004

-22

-188

2004

2005

-45

-233

2005

2006

-40

-273

2006

2007

-18

-291

- 79 -

1991-1989

1993-1991

-14

1995-1993

1997-1995

-109

1999-1997

-34

2001-1999

-29

2003-2001

-85

2005-2003

-67

2007-2005

-58

Appendix 2 â&#x20AC;&#x201C; Lichenometry data: Moraine 1, 2 and 3.

- 80 -

Appendix 3 â&#x20AC;&#x201C; Dendrochronology data: Moraine 2 and 3.

Moraine 2 Location on Moraine

Altitude

Ring

Year

Substrate

Age

Girth

Height

Girth:Height

(North/South/Crest)

(m.a.s.l.)

Age

Exposed

Age

Difference

(cm)

(m)

(cm)

(m)

2394

0.41

3.52

11.65

0.12

0.02

2286

1942

0.42

3.48

12.07

0.12

0.02

2295

1949

0.24

1.79

13.41

0.13

0.02

2318

1955

0.16

1.45

11.03

0.11

0.03

Girth:Age

2232

1936

0.36

4.62

7.79

0.08

0.01

2270

1942

0.55

5.76

9.55

0.10

0.02

2261

1936

0.64

6.61

9.68

0.10

0.01

2256

1936

0.49

8.02

6.11

0.06

0.01

2249

1936

0.69

6.79

10.16

0.10

0.01

2241

1936

0.64

6.40

10.00

0.10

0.02

2221

1934

0.55

5.71

9.63

0.10

0.02

2215

1934

0.34

4.72

7.20

0.07

0.01

2211

1934

0.41

5.98

6.86

0.07

0.01

2210

1934

0.44

7.07

6.22

0.06

0.01

2208

1934

0.79

8.52

9.27

0.09

0.02

2213

1934

0.72

11.20

6.43

0.06

0.02

2233

1934

0.66

9.01

7.33

0.07

0.02

2244

1934

0.49

6.40

7.66

0.08

0.01

2247

1934

0.54

8.15

6.63

0.07

0.01

2246

1934

0.43

5.23

8.22

0.08

0.02

2234

1934

0.66

9.37

7.04

0.07

0.01

2238

1934

0.60

7.54

7.96

0.08

0.01

2227

1934

0.66

8.73

7.56

0.08

0.02

2210

1934

0.47

9.38

5.01

0.05

0.01

2208

1932

0.74

11.41

6.49

0.06

0.01

2207

1932

0.72

9.87

7.29

0.07

0.01

2216

1932

0.53

8.03

6.60

0.07

0.01

2216

1932

0.58

8.35

6.95

0.07

0.01

2214

1934

0.73

9.66

7.56

0.08

0.02

2209

1932

0.72

11.88

6.06

0.06

0.01

2200

1928

0.62

9.30

6.67

0.07

0.01

N/C

2201

1930

0.69

9.73

7.09

0.07

0.01

2201

1928

0.75

9.87

7.60

0.08

0.02

C/s

2225

1934

0.54

9.88

5.47

0.05

0.02

2213

1934

0.63

11.37

5.54

0.06

0.01

2200

1928

0.60

10.91

5.50

0.05

0.01

2216

1934

0.54

9.72

5.56

0.06

0.01

2235

1934

0.71

8.45

8.40

0.08

0.01

2231

1934

0.65

8.16

7.97

0.08

0.01

2237

1934

0.64

7.62

8.40

0.08

0.01

2242

1934

0.75

9.12

8.22

0.08

0.02

2248

1936

0.73

8.67

8.42

0.08

0.02

2265

1936

0.70

8.26

8.47

0.08

0.02

2273

1936

0.76

9.47

8.03

0.08

0.02

- 84 -

2276

1942

0.56

5.78

9.69

0.10

0.02

2306

1934

0.68

7.53

9.03

0.09

0.02

2205

1934

0.55

9.84

5.59

0.06

0.01

- 85 -

Moraine 3 Location on Moraine

Altitude

Ring

Year

Substrate

Age

Girth

Height

Girth:Height

(North/South/Crest)

(m.a.s.l.)

Age

Exposed

Age

Difference

(cm)

(m)

(cm)

(m)

Girth:Age

2297

0.63

6.08

10.36

0.10

0.02

2292

0.52

4.55

11.43

0.11

0.02

2295

0.72

5.48

13.14

0.13

0.02

2289

0.60

7.36

8.15

0.08

0.02

2278

0.74

6.15

12.03

0.12

0.02

2268

0.49

6.31

7.77

0.08

0.01

2257

0.67

5.03

13.32

0.13

0.02

2249

0.75

9.13

8.21

0.08

0.01

2248

1916

104

1.04

14.96

6.95

0.07

0.02 0.01

2247

1916

0.96

15.72

6.11

0.06

2247

1914

0.96

13.19

7.28

0.07

0.01

2240

1916

0.73

10.88

6.71

0.07

0.01

2237

1916

0.64

10.52

6.08

0.06

0.01

2232

1914

0.82

12.79

6.41

0.06

0.01

2225

1914

104

1.04

14.16

7.34

0.07

0.01

2225

1912

125

1.25

14.28

8.75

0.09

0.02

2227

1912

116

1.16

15.23

7.62

0.08

0.01

2224

1912

0.78

13.46

5.79

0.06

0.01

2220

1910

102

1.02

15.64

6.52

0.07

0.01

2218

1912

100

1.00

14.32

6.98

0.07

0.01

2213

1912

0.74

13.54

5.47

0.05

0.01

2208

1912

0.76

13.74

5.53

0.06

0.01

2202

1910

105

1.05

15.36

6.84

0.07

0.01

2205

1910

0.91

14.89

6.11

0.06

0.01

2209

1910

107

1.07

15.34

6.98

0.07

0.01

2216

1908

0.84

13.59

6.18

0.06

0.01

2214

1908

0.98

15.14

6.47

0.06

0.01

2210

1908

0.98

15.69

6.25

0.06

0.01

2206

1908

0.81

13.42

6.04

0.06

0.01

2198

1908

0.87

14.63

5.95

0.06

0.01

2197

1910

0.76

14.06

5.41

0.05

0.01

2193

1908

0.84

14.53

5.78

0.06

0.01

2188

1908

105

1.05

16.65

6.31

0.06

0.01

2184

1908

0.78

13.56

5.75

0.06

0.01

2186

1908

0.84

14.57

5.77

0.06

0.01

2192

1906

101

0.77

14.85

5.19

0.05

0.01

2190

1906

101

0.76

14.63

5.19

0.05

0.01

2181

1904

103

0.94

15.89

5.92

0.06

0.01

N/C

2185

1904

103

0.83

15.12

5.49

0.05

0.01

2184

1904

103

0.95

15.74

6.04

0.06

0.01

2183

1904

103

1.03

16.34

6.30

0.06

0.01

C/N

2179

1904

103

0.92

15.58

5.91

0.06

0.01

2178

1904

103

0.89

15.46

5.76

0.06

0.01

2211

1910

0.75

13.26

5.66

0.06

0.01

2224

1910

0.79

13.03

6.06

0.06

0.01

- 86 -

Appendix 4 â&#x20AC;&#x201C; Treeline data

Treeline outposts Location within valley relative to foreland Southside (M2) Southside Northside (M2/3) Northside (M3/4)

Altitude (m a.s.l.) 2394 2420 2390 2403

GPS position x 602452 602513 602268 602238

- 87 -

y 095944 095802 096235 096327