Inside this issue What’s Behind that Council Tree, Pg.6 Pruning Research Update:, Pg.10 Fake Plastic Trees, Pg.14 Lightning Strike, Pg.22 Engaging with the public, Pg.28 The Stockholm System, Pg.32 Zelkova serrata “City Sprite”. Pg.40 Shrub species for carbon uptake, Pg.46 And Finally, “community engagement”, Pg.51
The bark of Zelkova serrata, this editions featured tree.
The Axe to Grind, Summer 2015 Edition. Interactive content; where you see the leaf logo then the page is ”live” so click for any internet content, try it
Meet this edition’s contributors If you click on any of the pictures you can read their online biography via LinkedIn
.
Where you see “Feature Article” the piece is unique to the Axe! We need more authors so please email if you have something to say or click on the question mark below.
Britt-Marie Alvern
Bjorn Embren
Francesco Ferrini
Julia Lock
Michelle Sutton
Glynn Percival
David Vickers
You?
Please don’t forget to visit the MTOA’s sponsors too.
The Chairman’s Stump.
Chair Matt Seabrook
Chair-Elect Gareth Hare
Past Chair Moray Simpson
Secretariat David Beadle
Treasurer John Blessington
CAVAT Rep. Andy Allison
Editor
MTOA Chairman, Matt Seabrook of Telford and Wrekin Council
Ian Mcdermott
AFAG Rep. Tim Weatherill
GYTOG Rep. Tim Bryant
Directors Andy Shervill Simon Smith Portia Howe Steve Dores Front cover picture. Foliage of Zelkova serrata.
T
here are of course many factors to consider when we look at a tree for whatever reason, some of them obvious and spring to mind instantly while others take thought and consideration and even then don’t necessarily become apparent. A tree that has been planted and survived the rigours of those juvenile years, made it to a self supportive stage where watering and stake or guying supports are no longer required has also attained a status where it is developing some prominence in the landscape, be it a focal point, part of a wider planting scheme or a visual barrier to buildings, softening the hard lines and encouraging wildlife. These initial observations are a start but we need to consider further as the ultimate aesthetics and purpose of the tree, its initial role is filled, I refer of course to all the other considerations the Councils need to make before the tree is even planted, from conception stage to maturity. Many trees are adopted following development and carry with them some maintenance funding to ensure their survival and continuation to a self
supportive stage. Others are planted as a managers’ can comprehend their worth. result of trees being removed or area There are a number of LA’s that have regeneration, whatever the reason these surveyed their tree stock using this method trees must now be considered as assets to but ultimately its the findings of the data that the LA and as such both looked after and must be both accepted and adopted by the managed accordingly if they are to contribute cabinet in order to both defend our actions to the area as intended and as desired. Some as Tree Officers and source the funding to trees of course are adopted as mature trees, proactively manage and increase our canopy having been developed around and included covers to reach a sustainable percentage within a land sale or cover. adoption. These trees Tree survey and data may well have been collection packages are subjected to tree expensive, requi re surgery (or should we training and usually say ‘investment’) so as have an annual licence to ensure they are fee attached. They take better suited to their time to populate and new environment and are only ever as good do not encroach upon as the operatives using the way we live and them. They are however enjoy our lives. This of an essential tool for the course adds to its value Tree Officer, helping instantly and cannot be him/ her with their day overlooked. Some of to day enquiries and your tree stock may fall scheduling works for under continual Street tree planting is just the beginning of the their contractors. Such management such a journey for Tree Officer’s. software does require a pollarding, regular ‘buy in’ from all the reductions or crown stakeholders and departments within the LA lifting for Highway clearance and previously that have trees within their responsibility in considered ‘best practice’ techniques that order for the LA to have a collective legal have resulted in prominent trees within the defence, so its not just the department that urban settings. These too have to be the Tree Officer sits in, it has to encompass considered as a monetary investment to your the entire LA. Approaching the insurance asset which of course boosts its value, department for a contribution in order to adding weight (and pound signs) to the value reduce claims and payments has proved of its retention. effective for some LA’s and others have The i-tree modelling software package that increased their section 106 contributions for is currently being championed adds weight to adopted land where possible, even including urban trees, their values and their the costs of felling and making safe areas importance in our lives. It indicates our affected by outbreaks of Ash dieback. canopy cover and urban forest structure, Councils are made up of various departments estimates the amount of pollutants (in with various roles, be it Parks, Leisure, tonnes) that trees filter out of our Neighbourhood Services, Adult and Social atmosphere and puts a monetary value to (Continued on page 8) them which is often the only way some ‘asset
the Tree Officer in his role and defend his actions.
(Continued from page 7)
Care, Open Spaces, Estates, Assets and Investments, Culture and Insurance these portfolios and stakeholders go on, and on. It is however knowing which service area to approach that ultimately decides the “ level of care each particular tree is afforded.
Where budgets are constantly being reduced as the belt of austerity tightens and with the assets we manage continually increasing in size and population our roles become ever more d e m a n d i n g a n d challenging. We now live in an increased claim culture where trips and slips are becoming commonplace and a compensation award is now expected, the pressure to remove trees increases daily. In order to fulfil our roles and increase the canopy cover for the benefit of all affected the only thing left for us to do is educate the ignorant, quite possibly the highest hurdle to jump, everyone ‘loves trees but....’
“The Tree Officer now has to consider the ‘health and wellbeing’ of the people living and working in their area”
The Tree Officer now has to consider the ‘health and wellbeing’ of the people living and working in their area and this is an increasingly supported approach by LA’s to retain trees where possible given that they are shown to reduce medical conditions (respiratory), improve recovery rates following illness or surgery and thus reduce expenditure through contributions to NHS organisations.
Given the LA (as with all land owners) and their associated ‘duty of care’ to users, visitors and passers by the local Tree Officer is often looked to as the single point of contact for a wealth of information, legislation, safety considerations, best practise advise and general tree biology queries, it falls to us to apparently know all there is to know about trees and the risks they present to everyone in their respective boundary area. At some point the tree will require consideration as to its rating, safety, survey interval and prominence. It is at this point that all the aforementioned ‘departments, portfolios and stakeholders’ must come together and collectively adopt a ‘tree safety strategy / policy’ and ‘Tree and Woodland management’ plan. These documents will determine the approach and legally defensible stance that will ultimately back up
Be it Parish Council meetings, local residents groups, press releases, leaflet drops, school visits, display boards or TV appearances the profile of the tree requires promotion. I for one of course am more than happy to oblige, like most of you I chose this profession because I love trees, find them to be fascinating, challenging and rewarding, but looking back through my ‘job description’ half of the things I’ve mentioned aren’t in there, we do it because we care. So when someone next says- “it’s just a tree” we should explain what’s actually behind the tree and why it’s there.
Matt Seabrook MTOA Chair
As if to prove many of Matt’s words in the previous article prophetic, the following is a timely reminder off the importance of the municipal Tree Officer.
School fined for failing to engage competent tree firm after untrained worker seriously injured and will be confined to a wheelchair for the rest of his life. An investigation by the Health and Safety Executive (HSE) found the school failed to engage competent contractors to undertake the arboriculture work, and that Mule failed to undertake a risk assessment for the work.
A
private preparatory school and its contractor have been ordered to pay over £110,000 after a man suffered permanent spinal injuries while felling a tree on the school's grounds. The unnamed 59-year-old man was using a chainsaw to fell a mature sycamore tree at Bassetsbury Manor, Buckinghamshire, home to Crown House Preparatory School, on 22 April 2013.
There was no safe system of work in place, it was not adequately segregated when members of the public were nearby, no ropes were used, and the ladder was not secured. lpha Schools Limited was fined £35,000 and ordered to pay £25,000 costs after pleading guilty to breaching the Health and Safety at Work etc. Act 1974. It also agreed to pay an ex gratia payment of £50,000 to the injured worker. Paolo Mule, trading as P&X Complete Cleaning Services, was given an 18-month prison sentence suspended for two years and ordered to pay £2,000 costs after pleading guilty to breaching the Management of Health and Safety at Work Regulations 1999.
He was helping one of the defendants, Paolo Mule, of P&X Complete Cleaning Services, which had been contracted by the school's owner Alpha Schools to clear a site for building After the case, HSE principal inspector Karl work. Howes said: "Arboriculture work remains highAylesbury Crown Court heard today (5 June) risk, particularly at height, and must only be that a large partially cut branch swung down undertaken by competent and trained and hit the ladder on which the worker was standing, throwing him to the ground where he contractors. All businesses have a duty to ensure they engage in competent contractors landed on his back. He is now unable to walk when carrying out tree work."
by Michelle Sutton Photos courtesy of the authors of Structural Pruning: A Guide for the Green Industry (Urban Tree Foundation 2013)
S
tudying tree pruning
Storms, Risk, and Where to Prune
Current and Future Research
Getting the Word Out
(Continued on page 12)
(Continued from page 11)
Fake Plastic Trees Julia Lock
“The true meaning of life is to plant trees, under whose shade you do not expect to sit.” - Nelson Henderson.
In
1995 Radiohead sung of fake plastic trees and a dystopian fake plastic earth. At this time of technological naivety who would have guessed that 20 years on we would have the possibility of this very concept becoming a reality? In the fight against global warming and the ever rising carbon dioxide levels, which now fluctuate around 400 parts per million, Klaus Lackner, director of the Lenfest Center for Sustainable Energy (Columbia University), has designed an artificial tree which will act to absorb the greenhouse gas from the atmosphere. The approach quite simply involves a honeycomb structure of leaves containing sodium carbonate which reacts with carbon dioxide to form the innocuous bicarbonate (baking soda). This is a chemical reaction that has been known well before the 1940s and is currently used in CO2 scrubbers. These artificial ‘trees’ are said to be able to reduce atmospheric concentrations
by 0.5ppm per year and are believed to be more efficient than trees at this role. Although this is a feat of ingenuity we should be careful to consider that this seemingly idyllic solution will have its drawbacks, which will revolve around the production and maintenance of the technology. The dawn of these advancements should not diminish the importance of a healthy and diverse canopy of trees in an urban environment. Even though this may be a feasible option the tree health agenda still needs to be pushed with the benefits of trees being utilised to their maximum. Trees are well known for reducing the adverse effects of the urban environment with its towering buildings, heat pockets and impermeable surfaces. If the correct trees are strategically planted in a place which is suitable to the species and their purpose they can serve the area well.
The lyrics “Hot town, summer in the city” by Lovin’ Spoonful strikes a chord with anyone venturing into the sprawl on a sunny day as urban surfaces absorb and retain heat. With this occurring over the expanse of a built up area it gives rise to the Urban Heat Island effect where temperatures are comparably higher than the surrounding rural landscape. This has vast implications with summer time energy demands soaring due to cooling and ventilation demands. Trees have evolved canopies of photosynthesising leaves that spread out to maximise their ability to capture sunlight. This canopy can mitigate increases in heat through shading and evapotranspiration of water with reductions in air temperatures between 2-8°C, and ground temperatures becoming 15-20°C lower (Saito, 1990-91, cited in Doick and Hutchings, 2013).
If the urban landscape did not benefit from the cooling nature of trees air conditioning and ventilation units would work overtime, increasingly pumping out toxic pollutants and greenhouse gases. There also would be limited control of Volatile Organic Compounds evaporating in the heat of the day and a build up of ground level ozone which is easily trapped by stagnant air conditions. Having spent some weeks in Beijing (China) the atmospheric cloud of smog is not to be taken lightly! This is a prime example of the conditions leading on to chronic respiratory health problems that go hand in hand with a depletion of breathable air. Pollutants trapped within the confines of the urban environment can be reduced with cooling and filtered out of the air by trees resulting in improved quality. This was apparent on a day of (Continued on page 16)
Figure 1: Diametrically opposed extremes in air quality; Left: Air thick with pollution particulates in the busy Beijing Olympic Park (Chaoyang District) creating a post apocalyptic feel; Right: Yonghegong Lama Temple (Dongcheng District) with noticeably good air quality for spiritual visitors to breathe.
(Continued from page 15)
bad air quality when visiting the Lama Temple (Figure 1). As well as being deleterious to the human population the Urban Heat Island can also cause stress to downstream aquatic ecosystems due to the addition of excess heat through storm water runoff. Meanwhile storm water in itself can be a problem with runoff rates increasing due to impermeable surfaces. A good healthy canopy can give welcome relief and offer a natural umbrella to pedestrians caught in a downpour. The leaves and bark of trees slows down the progression of the rainfall to ground level, whilst trees roots absorb ground supplies of water which is eventually released once again to cool the atmosphere. This interception of rainfall can help aid the issue of rapid runoff which often causes flooding and the influx of polluted water downstream. Interception of water by trees has been mathematically calculated to be 6.6m3 per tree on average, ranging from 0.8m3 to 20.8m3 depending on species (Xiao and McPherson, 2003), and thus trees are vital in this respect. The green utopia created by a mosaic of trees and Public Open Spaces across the urban environment helps to provide the above benefits to the immediate surroundings as well as seating towns and cities in the wider landscape. In a fragmented world caused by urban sprawl green areas provide ecosystem services to wildlife. They can also be utilised as hopping stones to those travelling further afield in search of resources. Harmless solitary bees providing pollination services can travel between 1100 and 1400m when foraging (Zurbuchen et al, 2010). Meanwhile in the US Monarch butterflies flutter their way across thousands of miles until alighting upon a milkweed leaf! The facilitation of nature’s movement makes for pleasant environs for the human popu-
lous who are made up of residents and commuters. It is now becoming clear that street trees can benefit people suffering from various degrees of mental health by increasing their sense of well being. Taylor et al (2015) found that increases in urban street tree density correlates with a decrease in prescription rates in London, UK. The opportunity to alleviate stress and anxiety by taking a walk in a ‘natural’ setting and creating happy hormone serotonin is far better in the long run for both an individual and the health service. In essence urban plantings of trees can be beneficial in many ways. The importance of their presence needs to be acknowledged with strategic planning of their placement brought to the forefront. The aim should be to plant healthy and resilient trees so that they can be of service locally and as part of a wider green network. If technology, such as the artificial trees, is to be implemented in areas it is vital to retain the provision of the natural attributes discussed. With sympathetic integration of inventive solutions a focus should be on the maximisation of positive outputs to the environment and whilst keeping inputs to a minimum. Tune in next time for a piece on tree health and SCEPTRE. Author: Julia Lock, PhD Researcher at the University of Northampton. Funding from the Thomas Harrison Trust. PhD revolves around the treatment of Specific Replant Disease on Sorbus aucuparia.
LinkedIn:
Moulton College:
Sources: Saito, I. (1990-91) Study of the effect of green area on the thermal environment in an urban area. Energy and Buildings, 15: 493-498. Cited in Doick, K. and Hutchings, T. (2013), Research Note: Air temperature regulation by urban trees and green infrastructure, Forest Research, UK.
study in London, UK, Landscape and Urban Planning, 136: 174-179. Urban Heat Island Basics, EPA (2008), Reducing Urban Heat Islands: Compendium of Strategies, U.S. EPA.
Xiao, Q. and McPherson, E. G. (2002), Rainfall interception by Santa Monica’s municipal urban Harte, C. R., Baker, E. M., and Purcell, H. H. forest, Urban Ecosystems, 6: 291-302. (1933), Absorption of carbon Dioxide in SodiZurbuchen, A., Landert, L., Klaiber, J., Muller, um Carbonate-Bicarbonate Solutions, Industrial A., Hein, S., and Dorn, S. (2010) Maximum forand Engineering Chemistry, 25(5): 528-531. aging ranges in solitary bees: only few individuTaylor, M. S., Wheeler, B. W., White, M. P., Econ- als have the capability to cover long distances, omou, T. and Osborne, N. J. (2015) Research Biological Conservation, 143(3): 669-676 note: Urban street tree density and antidepressant prescription rates – A cross-sectional
Greater Lyon Tree Charter: The English version is now available! The Greater Lyon Tree Charter is now available in English. The Charter was designed by the Greater Lyon Authority as a partnership-building tool to enhance the long-term management of trees across France's third largest city. It offers a set of common principles, together with a powerful rationale for action and a rich set of ideas for implementation for wide ranging audiences. So far, over 100 local and national stakeholders (including Greater Lyon's 59 boroughs, utility companies, the French equivalent of the UK's Landscape Institute, some tree nurseries, etc.) have signed the Charter, committing themselves to adhere to its Principles and to develop their own action plan for implementation. Both the approach and the recommendations featured in the Greater Lyon Tree Charter are highly relevant and directly applicable to the management of trees in towns and cities on this side of the Channel! Click here or on the image to download your copy.
Greening Grey Britain The Royal Horticultural Society (RHS) launched its Greening Grey Britain report at the Chelsea Flower Show on Monday 18 May 2015 highlighting an alarming trend of Britain paving over its front gardens and not growing any plants in them. The RHS 2015 Greening Grey Britain Report reveals that three times as many front gardens are paved over compared to ten years ago, a total increase of 15 square miles of ‘grey’, and that plant cover in front gardens has decreased by as much as 15%. Over five million front gardens now have no plants growing in them, 7.24 million are nearly totally paved over and four and a half million front gardens are completely paved over. Today one in four UK front gardens are completely paved over and nearly one in three front gardens has no plants. The RHS believes it is vital to reverse this trend for the nation’s health, for wildlife, to mitigate against pollution and heat waves and to protect the UK’s homes from flooding: https://www.rhs.org.uk/science/gardening-in -a-changing-world/greening-grey-britain
Tree safety legislation and developing your policy 2 and 3 July Plant Network training event at Yorkshire Arboretum, Castle Howard. This 1.5 day training session will introduce the relevant legislation and resources available. Large and small organisations will outline, how they have developed their own tree safety usage zones, inspection procedures and policy documents and share experiences and best practice. Delegates will have the opportunity to work with experienced policy developers and over the session start to draw up a tree safety policy for their site: http://plantnetwork.org/news/bookingopens-tree-safety-legislation-developing-policy/
Root fungi help trees cope with road salt, say researchers Arbuscular mycorrhizal (AM) fungi can help street trees cope with the stress of de-icing salt in their rootzones, Austrian researchers have claimed. The team from Vienna's University of Natural Resources and Life Sciences inoculated half of a population of wych elm (Ulmus glabra) seedlings with commercial AM spores, then treated some of each with a salt solution, and measured root respiration and biomass accumulation. "The salt treatment significantly reduced the biomass of non-inoculated seedlings [but] biomass of AM plants was not significantly affected," they said. However, "without NaCl stress the mycorrhizal plants tended to grow less than the non-inoculated due to the cost of having mycorrhiza", they added. They concluded: "Commercial AM inoculate can prevent a major increase of root respiration under moderate NaCl stress, enabling trees to deploy more assimilated carbon for growth and, theoretically, defence mechanisms against other stress factors occurring in urban environments." The results are published in Urban Forestry & Urban Greening.
Caterpillar web infestation threatens town's street trees A Midlands council has said it may have to remove street trees that are infested with caterpillar webs, even though the webs are harmless and the trees still apparently healthy.
Ermine moth damage - image: Per Erik Strandberg
Corby Borough Council said that the cherry trees, on the town's Cottingham Road, were infested with ermine moth (Yponomeuta sp.) larvae for a second year running, leaving them defoliated and covered in webs. "These caterpillars are not hazardous to human health but can cause significant damage to trees long term which could result in them eventually needing to be removed," the council said in a statement. "We are working with external consultants to see if there are any possible solutions to break the cycle of the caterpillars returning and will continue to monitor the situation." http://www.newsflare.com/video/47748/weather-nature/caterpillar-infestation-in-corby-uk? utm_source=Newsflare+Members&utm_campaign=fe4b6b22ebCATERPILLAR_INFESTATION_IN_CORBY&utm_medium=email&utm_term=0_41f57e52e3-fe4b6b22eb-110406445
LIGHTNING STRIKES
Lightning strikes can cause serious damage to trees rendering them a potential danger to the public and traffic. In this article Drs Glynn Percival and Tom Smiley discuss the dangers of lightning strikes on trees and results of their experiments investigating standard and experimental lightning protection systems. Introduction Human deaths resulting from lightning strikes are a rare occurrence. For example records on lightning fatalities show that in the United Kingdom an average of 0.2 deaths per million population as compared to 0.6 in the United States, 1.7 in Singapore and 1.5 in South Africa. A breakdown of these fatalities shows most deaths occurred while the victims were taking refuge under a tree. This then begs the questions, why does lightning hit trees so frequently and why if we are sheltering under a tree would the lightning move from the tree to strike us? What is lightning and why does it frequently hit trees? Lightning is an electrical discharge that results from the buildup of positive and negative charges within a thunderstorm. When the buildup becomes strong enough, lightning appears as a "bolt" either within the clouds or between the clouds and the ground. Most lightning passes through trees on the way to the ground, because the
moisture (sap and water) inside a tree is a much better conductor than air i.e. electricity seeks the path of least resistance. The water in a tree is concentrated near the cambium just under the bark. As the electricity from the lightning surges through this water, it causes it to boil explosively (lightning temperatures approaching 27000oC can occur in a split second), “blasting off� the bark, throwing pieces of it in all directions. The reasons why humans sheltering under trees are struck is because of what is known as lightning "side flash". Side flash occurs when a person standing near a tree during a lightning discharge in essence becomes a more convenient conductor for the electric current to the ground. Damage to trees The effects of lightning on trees are variable. Some will be severely damaged with much splintering and shattering of wood and bark whereas others will suffer little or no apparent external injury. Lightning may kill
trees immediately; others, even though copper and copper bronze. Note not all damaged extensively, will continue to grow. metals can be used as conductors. For Occasionally, trees example aluminum will continue to materials are not appear normal recommended for immediately use in tree lightning following the strike protection systems. but may die several These conducting weeks or months systems need to be later. This usually adequately ground results from root normally to a ground injury which is not rod again based on apparent. Often, the copper or bronze. tree will not be killed The type of instantly, but the grounding system open wound created varies based on soil by the lightning type and the physical strike is an invitation character of the to insects and fungi surrounding area. that can ultimately Groups of trees can cause its death. It is also be protected by actually it is the installing conductors duration of the on the major trees lightning bolt that and common determines how grounding them all destructive it will be. by trenching from the "Cold" bolts are base of each Lightning strike on oak characterized by protected tree to the high electrical driving grounding current and connection. extremely short duration. One of these penetrating to the heart of a tree can convert it instantaneously Research at the R.A Bartlett Tree Research to kindling. "Hot bolts are of lower electrical Laboratory current but slightly longer duration and are Although lightning protection has more likely to cause fires. For example, it is successfully been installed in trees for over estimated about 7500 forest fires are started 50 years, there is little research about the this way in the US each year. It is also a myth materials used in systems or the effect on that lightning never strikes twice in the same trees that have been struck. There is place. In fact, lightning will strike several anecdotal evidence that protected trees times in the same place in the course of one suffer little or no damage if struck. Due to discharge. this lack of visible tree damage, the question that often arises is, “How do I know if my lightning protection system has been Lightning Protection struck?� The best way to protect trees from a similar One way of determining if a tree is struck is fate is to have lightning rods installed. The to incorporate a fuse into the system. lightning rod is a simple and effective device Interestingly there are no standard fuse to protect trees. It works on the principal systems recommended for tree lightning that the metal of the lightning rod provides a protection systems. While fusing a lightning superior conductor than the moisture in the protection system sounds like an easy task, trunk, so the lightning bolt is guided down to in reality it is more difficult than it appears. earth without injuring the tree. A range of The simplest method of fusing would be to lightning conductors exists including cut the conductor and install a fuse between standard, secondary and miniature down, the two cut ends. This is not a safe practice conductors normally based on gauge copper because the fuse may actually explode when wiring and air terminals also based on
(Continued on page 24)
(Continued from page 23)
hit or tree damage may occur when the electricity jumps the gap. Instead of directly fusing the system, the typical way lightning protection is studied, is by making wire loop with a flash bulb installed as a fuse. However, there are problems finding flash bulbs in this day and age and durability problems when they are attached to a tree. Lightning protection fuse systems work on the same principal as a transformer. As the lightning charge comes down the conductor, a current is induced in the wire loop, blowing the flash bulb or fuse. The more coils of wire present, and the closer they are to the conductor, the greater the current through the coil. Induced current is directly proportional to the number of wire coils.
We had a two-coil system with a one-amp fuse and a nine-coil system with a three-amp fuse installed on the pine tree. The threeamp fuse blew; the one amp fuse did not. This leads us to the conclusion that we need at least three coils per fuse-amp to ensure enough induced charge to blow the fuse (Figure 1). With this as a minimum, we decided to overdesign the system in order to make sure that a lower amperage lighting strike would still blow the fuse.
To build these fuse systems the material required is a marine quality fuse holder, a one-amp fuse, two corrosion resistant nylon butt connectors, two cable ties, and 90 cm of marine-grade 18-gauge insulated wire. The wire is connected to the fuse leads using the nylon covered crimp connectors. The assembly is coiled around the hand to Figure 1. Lightning protection create five loops that are about 9 system fuse setup Over the past three years, dozens cm and 4 cm across (Figure 2). of standard and experimental The fuse system is then tightly lightning protection systems have attached to the lightning been installed at the Bartlett Tree protection conductor using cable Research Laboratories in the US to study the ties. To see if a protected tree has been effects of lightning on tree crowns, roots, struck, open the fuse holder and look at the and lightning protection conductors. Along fuse. with the lightning protection systems, a variety of fuses At present we are not have been installed to monitor recommending the installation lightning strikes. These fuse of experimental lightning systems range from protection systems. The commercially manufactured systems installed at the lightning strike counters to Bartlett Tree Research simple looped fuse holders. Laboratory are designed under controlled conditions where On April 2, 2012 one of our consequential tree damages experimental conductor are not a factor. We are systems in a 20 metre tall presenting this information so loblolly pine was struck during that interested readers can a lightning storm. The system make and install fuses on had two fuses installed on it; trees that are protected by a one of which “blew� and the lightning protection system. Figure 2. Loop the fuse wire three to other did not. This fact gives With data from systems that five times around you hand to form the us some extremely valuable have been struck, much can be necessary coils. information on fusing learned about how lightning lightning protection systems affects both trees and the systems that and methods for monitoring and protect them. This type of research may lead documenting strikes. to lower cost lightning protection systems and more trees being protected from this Instead of using flash bulbs, our system uses potentially devastating force of nature. an automotive type fuse and a coil of wire.
Other factors to take into account While it may be impractical to install a rod in every tree on your landscape, you may narrow down the list of trees that must be protected from lightning by considering these factors: 1) Species of tree - Oaks, elms, pines, spruce, poplars, maples and ash are most likely to receive a lightning strike. Likewise trees that stand alone, rise above other trees or that are close to water are most frequently struck. Beech, birch and horsechestnut receive the fewest strikes. Beeches may be less damaged by lightning because they contain large amounts of oil (a poor conductor of electricity) and because their smooth bark forms a continuous sheet which
electricity can flow down without harming the internal tissues of the tree. Oaks, on the other hand, are more likely to be damaged since their wood has a high water content. 2) Height of tree and its proximity to your home. Would lightning damage to trees endanger your safety or damage valuable property? If you are not sure whether or not you may require lightning protection, your best defense is to have a certified arborist inspect your trees and provide expert advice.
Dr Glynn Percival Bartlett Tree Experts
Lightning protection
District Council Managed A local cemetery with a boundary lined by large mature Limes. They were topped after complaints About shading, please note the shadows in the photo. Are not on the properties.
Metropolitan Counc
Land sold off to raise fun were not informed and street trees had value. T
cil (Unitary) Managed
nds but the Tree Officers d no one though that the Two weeks later—topped
University Managed Grounds team topped the Cherries and oddly they are now riddled with Chondostereum.
Engaging with the public in open spaces David Vickers explores the rising interest in chainsaw carving and finds out why it might be of interest to municipal areas.
A
bout four to five years ago, a friend of mine moved away from forestry training and whilst I remain in that part of the industry, Chris Bain has shifted his skill set to start a much more creative business – chainsaw sculpting. I’m sure we’ve all seen the outpouring of wooden mushrooms at garden centres, countryside shows and in lay-bys, but there is also a growing industry in creating wonderful artworks from timber by using a chainsaw. Currently, there are only a few high-end chainsaw carvers but the work they do is in
demand from parks and gardens, both public and private. It’s a world away from felling trees and carrying out arboricultural operations, and about the only thing that is the same is the main body of the chainsaw. This is chainsaw use like never before, and that skill seems to attract a growing appreciation from the public. I caught up with Chris, at Avington Park in Hampshire, and owner Sarah Bullen, as he started to carve two hippopotami from a tree that was uprooted in high winds. I started by asking Sarah why she wanted the timber
sculptures in the grounds of the stately home, “well, I thought it was kind of fun to have the hippo’s as we have the fields and the river running through them – and hippos love both land and water!”. Avington Park is open to the public from May to September, and is also available for corporate events, weddings and as a film location; I wondered whether there were any other benefits to having these chainsaw sculptures, “I’m hoping that they will be an attraction in their own right”, explained Sarah, “there will be two of them, one standing in the field near the water’s edge with another hippo actually in the river. I think it’ll be a real talking point for the public – especially if my friends comments are anything to go by!”. So, with clearly perceived benefits to public spaces, I asked Chris what thoughts he had on this fledgling industry, “it’s early days
over here… the industry is much more advanced in the U.S. and there are many more tools available to the chainsaw carver over there. But times are changing, there’s really only a few of us in the U.K. able to complete the larger scale projects but the public interest is huge.” Apart from the chainsaw skills required, and the spacial awareness to convert a picture in your head to a 3-dimensional sculpture, Chris summed up why he loved his new found vocation, “it’s all I want to do now, I love the creativity, I love working with the timber, trying to assess how I can use it’s natural qualities to enhance the final piece, and I love that the public seem to really engage with the sculptures”. That’s really why a stand-out feature like a chainsaw sculpture captures the public imagination, whether it’s a hippopotamus in the water, or a fantasy world castle complete with dragons; the use of a natural resource to bring a new world into view, something that the owner of Avington Park confirmed, “I also wanted these sculptures made from the fallen tree as the tree belonged to the Park, it was a real feature of the landscape and with these hippos, it will remain a feature of the landscape”.
David Vickers Drivelink Training
The “Bee Tree”
Björn Embrén and Britt-Marie Alvem
Aesculus hippocastanum ‘Baumannii’ in Erik Dahlbergsgatan 20012. The horse chestnuts were planted in 2004, then being 30-35 cm in stem circumference at one meter height. Nine years later the measurements show that they are now 70-83 cm.
M
ost of the trees in the inner city of Stockholm were planted a hundred years ago, when the roots still had space below ground and the trees were able to grow. During the following decades different cables and sewer systems have been fitted into the ground, the excavations and the airtight backfilling cutting off and damaging the root systems, and leading to declining street trees. The ground surrounding a street tree is heavily compacted and sealed off hermetically, causing the trees to suffocate. In July and August the leaves on many of the street trees will be brown, the trees sadly declining. The Traffic administration is responsible for the Street trees in Stockholm and during the last fifteen years the Stockholm system for building load bearing, structural soils concentrating on trees in the inner city’s
streets and squares. It has been carried out using local, crushed rocks and storm water is being used to irrigate the trees through inlets. The first sites were constructed in 2004 showing unimpeded root development and growth rates equal to trees in nurseries. Drawings and methods are collected in “Planting beds in the city of Stockholm 2009.02.23. – a Handbook”, and can be found on the internet. The Stockholm system has been inspired by different structural soil projects around Europe. Sites in the Netherlands and research on structural soil from the University of Hannover in Germany, and by various projects led by Klaus Schröder in Osnabrück, are the main sources for inspiration. Adding further ideas to creating a system was an article by Palle Khristoffersen and Kjell Nilsson in the magazine Utemiljö from 1998, where the described an aeration layer, on top
Newly planted Prunus ‘Umineko’ photographed in May 2013 in Kocksgatan. They were planted six months before in a newly built structural soil.
The same cherry trees photographed in August, three months later. The leaves are a lush, dark green colour, the crowns are dense and the shoots are growing fast.
of structural soil. Another vital source is the booklet “The oxygen requirement of plant roots in relation to soil aeration” by Edward Elway Free from 1907(!). The Stockholm system combines different ideas and added the air wells or inlets too the aeration layers, thus enabling gas exchange for the root system.
Multiple, thin layers of soil are then flushed into the voids between the stones, using a strong jet of water. The soil should have a low content of clay and organic matter to make it easier to flush into the voids. If stone fractions of inconsistent size are used or if the grade size is too widely spread, there won’t be enough voids for the roots to grow into.
In 2014 the structural soils were approved for heavy traffic by The Swedish National Road and Transport Research Institute (VTI), which means that they can be used below the streets and parking lanes as well as below the pavement. In Stockholm the local granite rock is used. Using local materials is vital to a sustainable city. Massive infrastructural worksites throughout the city ensure that there is access to crushed granite rocks of the adequate sizes. The construction is carefully carried out layer by layer. The size of the individual stones should be as even as possible. In Stockholm 100-150 mm grade size of angular stones that lock into one another when they are compacted are being used, thus creating a stable structure. Each layer is 300 mm thick.
When the two to three 300 mm layers of stones with flushed in soil have been completed, slow release fertiliser is put on top of the top layer to add some nutrients to the structure. Then the 200 mm aeration layer of washed granite 32-63 mm in grade size is fitted in. A levelling layer of washed granite stones 8-16 mm in grade size is put on top of the aeration layer. Levelling out the bigger stones is made to protect the geotextile that goes on top of the whole construction and separates the structural soil from the paving subgrade, preventing small particles to fall into the aeration layer, causing the voids to get clogged. Different kinds of air wells or inlets are fitted into the construction, enabling gas exchange (Continued on page 36)
1 The trench for the new structural soil has been dug out in a street in Stockholm
2 The first and second layer of the big for the structural soil has been fitte trench and compacted. Soil has been the voids of the first layer.
8 The paving is finished and the street is ready for planting
7 The subbase for the paving is put on top of the geotextile.
6 A geotextile is covering inlet is cover
gger stones ed into the flushed into .
g the aeration layer, and the red by a grate.
3 Soil is being flushed into the second layer of stones with water in a strong jet.
4 The inlet or air well is fitted in to the stones. The upper 20 cm of the inlet are perforated and the holes are in the same level as the aeration layer that comes next.
5 The aeration layer of smaller stones has been fitted in and so have the tree frames. Stones are falling into the tree frames, stabilising the construction.
The storm water is led via concave paving stones and collected into the air wells or inlets. From there the rainwater is distributed through the aeration layer down into the structural soil, irrigating the tree.
from the aeration layer and the bigger stones used for the structural soils should fall into the concrete crate in a natural slope or angle. This ensures further stability to the whole structure and prevents the paving closest to the tree pit from caving in. The root ball of the tree is positioned on top of the structural soil inside the frame. This keeps the tree positioned at the right level, and prevents it from being planted too deep. The space around the root ball is filled with soil mixed with porous pumice stones, also providing possibilities for gas exchange. The planting pit is then covered with a surface grid, in the same size as the frame, 1400 x 1400 mm. The tree is protected by a fairly wide metal tree guard (600 mm in diameter) to avoid damage to the stem. The tree guard can also be used for providing support to the
(Continued from page 33)
and irrigation using storm water. One inlet per tree or every two trees ensures that the roots are provided with oxygen and water and that the carbon dioxide is let out of the ground. If fitted correctly the holes from the inlet match the level of the aeration layer, and during rain the well is filled with water that is pushed into the aeration layer and thereby distributed into the structural soil. The water pushes the accumulated carbon dioxide out of the aeration layer and makes room for fresh oxygen. The well is equipped with a sand/silt collector to allow for periodic cleaning. The concrete frame or bunker keeps the paving in place and creates space for the root ball when a new tree is being planted. Stones
tree. The average new street tree is quite large: The stem circumference at 1 meter is 30-35 cm, and the stem height is 180-240 cm. Planting a larger tree prevents vandalism and ensures that branches don’t interfere with traffic. When replacing a tree in a row, the gap between the new tree and the old ones will be smaller. During the first two years after planting the tree is being irrigated, each tree gets at least 140 litres of water with 2 ppm of nutrients every two weeks between April and September. The trees are being fitted with water bags, allowing the water to percolate into the ground during eight hours. The trees are also checked and the pits are weeded regularly. The maintenance is crucial to being successful in tree planting.
Ideally the tree pits would be aligned, forming a tree trench stretching along the street so that the trees get a larger volume for their roots as space for unimpeded root development boosts tree growth. The trench could also be connected to green spaces close to the trench, such as lawns or parks. Declining lime trees in Tegelbacken 2010 with brown leafs and branches that have died back.
The lime trees have been retrofitted with structural soil, and two years later they show nice, dense crowns and good growth. (Two dead trees have been cut down.)
After two years the system is relying on storm water for tree irrigation; water from the pavement, street and surrounding roofs is led into the inlets and down into the structural soil. Using granite stones beneath the surface allows ground water condensation on the stones, and the roots are being kept moist even during the summer.
The structural soils can not only be used for new trees, but also for retrofitting around trees that need revitalisation. In such cases the old soils are carefully excavated with nonintrusive tools, and the different layers of the Stockholm system is carefully fitted in.
The Stockholm system is not technically complicated but rigorous implementation and supervision is of vital importance for a successful construction. Therefore monitoring during the design and construction is vital to getting a stable and functioning structural soil. Adaptions to the site should always be made: What material is the existing ground made of? Is there a high or a low groundwater level at the site? What kind of local materials can be used? Are those materials finite or infinite? The most common errors during the design and construction of the Stockholm structural (Continued on page 38)
(Continued from page 37)
soils is that the air wells are being fitted in at the wrong height or that geomembranes are put in the wrong place, for instance between the structural soil and the aeration layer. Geotextiles put in the wrong place prevent the system from operating effectively. Constructors often keep the stones from falling into the concrete frame, thereby making the construction unstable. Flushing the soil into the ground is time consuming and expensive. Sometimes the contractor tries to save money by buying ready mixed structural soil, which can’t be compacted. The Installation costs for the Stockholm system are quite high. But once it has been built it should be a long lasting solution. If the street trees that are being planted now have enough root volume to last for many, many years and thus providing those ecosystem services that a healthy, growing
tree does, then the costs should be seen as a sound investment. Adding the retention and cleaning of storm water used for irrigating the trees should also add further to the benefit-cost equation. By creating sufficient rooting volume and enabling gas exchange for tree roots below ground, not only well growing trees can be achieved but also costs for root damage to paved areas can be avoided. If trees are well provided for, and have enough oxygen and moisture, the risk for root intrusion in pipes etc. is less likely to occur. These are further economic arguments in the Stockholm system’s favour. The only maintenance costs for the irrigation system is the periodical cleaning of the inlet. Since the trees are growing well there will be costs for pruning if the trees grow large. Too large trees could probably be avoided by carefully choosing tree species that fit into the scale of the site or are classified as small to medium sized.
About the Authors Björn Embrén and Britt-Marie Alvem are tree officers working for the city of Stockholm. Together they manage 30 000 street trees for the Traffic administration in Stockholm. All images by Björn Embrén
The Stockholm Biochar Project For the last four years biochar has been used in Stockholm to enhance growth when planting trees, shrubs and perennials. Biochar retains air, water and nutrients in the soil substrates and thereby helps the trees to grow. It can also be used to filter out pollutants. Biochar is charcoal produced in a process called pyrolysis. In Stockholm it will be produced locally from garden and park waste that. The excess heat from the process is used for heating housing areas. The biochar is then used in different substrates for planting throughout the city. The project enables citizens to contribute to carbon dioxide sequestration by collecting residential garden waste for biochar production. They will then be able to mix biochar into their soils and get even better crops in their own gardens.
Now is ideal time to look for Chalara but don't be fooled, says FERA researcher Spotting Chalara ash dieback "is not as easy as it seems", a leading plant pathologist has admitted.
"Now is an excellent time to look for symptoms," Food & Environment Research Agency (FERA) pathologist Charles Lane said on the website of tree disease monitoring body Observatree. Describing his home area of rural North Yorkshire as "in the front line of the spread of Chalara Dieback of Ash", he said: "The most reliable and consistent symptom is the slightly sunken, foxy red-brown lesion centred on a side branch. This frequently causes the death of the leader, resulting in a flush of side shoots at the base as the tenacious ash tries to recover." But he admitted: "Even I've been fooled on several occasions in thinking that lower shoot dieback is due to Chalara. But this is frequently down to light starvation – looking for stem lesions is the key."
Mature trees pose a particular problem, he added. "Talking to my local Forestry Commission tree health officer Alan Ockenden, he recommended looking at foliage for signs of wilting in late June and early July. If he sees suspicious symptoms he'll check on regrowth and hedgerows, which are easier to see and sample." Lane has issued a free online video guide to identifying the disease.
Images: Forestry Commission
MTOA: - bringing you the best there is in educational training and at price that can’t be beaten, read below.
Ash Dieback “Down South” MTOA study tour, 29th and 30th July
F
or arbs working in the as yet unblighted regions of the UK, Ash dieback is limited to FC bulletins and newspaper articles with dodgy statistics (not like the one on the left, Ed.). This is your chance to see Ash Dieback in the wider environment at one of it’s first reported locations: Pound Farm near Framlingham in Suffolk. The property is owned by the Woodland Trust and they have kindly agreed to give the MTOA a guided tour of the site. Pound Farm includes much young planting but also includes areas of Ancient Woodland, old Pollards and mature trees. This allows the visitor to see the effects of Chalara on Ash in practically all stages of growth.
Woodland Trusts Mike Ryder who has been managing Pound Farm since before the outbreak. Mike will on hand to answer the groups questions about the effects of the disease and discuss the Trusts trial plots of resistant Ash. In the afternoon will be a visit to Staverton Deer Park to view ancient Oaks and Hollies For those travelling down the night before the group will meet in the bar of the Crown Hotel in Framlingham at 19.30 for light refreshments. Otherwise it’s a meet at 08.45 for 09.00 at the main entrance to Pound Farm for a prompt start as there’s lots to fit into the day.
Accurate identification of Chalara and taking the appropriate action will be critical in allowing arbs to manage the disease in the wider environment.
The event is free but is limited to 30 places so please book early to avoid disappointment. Contact Jean on 0121 556 8302 or email
Taking the group round the site will be the
Click for Map
Experts gather in Brighton to seek ways to safeguard elms Tree experts have called for Brighton's National Elm Collection to be given World Heritage Status, and for a certification scheme for new elm varieties claimed to be disease resistant. The Sussex seaside town, which is home to the UK's largest and most diverse elm population, last week hosted an elm conference organised by The Conservation Foundation which drew elm experts from across the UK as well as Germany and the Netherlands. Delegates visited elms in the town's Preston Park, home to a number of novel elm varieties which could have strong resistance to Dutch elm disease. They also discussed the disappointing per-
formance of several elm varieties introduced in the past 30 years, which lacked the disease resistance claimed for them, and proposed a "kite mark" to give confidence to gardeners, local authorities and national governments. The conference was part of The Conservation Foundation's Ulmus Maritima elm tree project, supported by the Heritage Lottery Fund and by Hillier Nurseries, which supplies the 'New Horizon' fully tested resistant elm. Caroline Lucas, Green Party MP for Brighton Pavilion, said: "Elms lend the city and landscape a distinct character and it's essential we do all we possibly can to protect them."
Conservation Foundation director David Shreeve said: "Brighton's elm population is amazing and still for many an unknown feature of its environment. Promoting its elms would bring visitors from far and wide and provide the city with a major added visitor attraction. It's important we build on the success of today's event."
Cambridge calls on public to help guide tree strategy Cambridge City Council has launched a "root and branch" public consultation on the city's trees to guide a strategy for their future management. The consultation seeks opinions on the council's approach to trees it manages in streets and open spaces, and also on privately-owned trees in the city.
An accompanying document points out that trees provide the city with economic, amenity, health, environmental and health benefits. Cambridge's tree canopy cover is a relatively high 17 per cent, compared with a national urban average of 8 per cent. Despite this, "there is scope for raising levels of coverage in all wards", it says. The survey will be open until 15 July, with results to be made available on the website shortly afterwards.
Proposal to fell Sheffield street trees prompts residents' campaign
A campaign has been launched to protect 12 mature street trees which Sheffield City Council has slated for felling due to pavement damage. The trees, believed to be all limes (Tilia sp.), stand on Rustlings Road next to Endcliffe Park in the west of the city. The council's highways contractor Amey has said they must be felled because they have damaged the pavement, and has undertaken to replace them. A petition on the change.org site to preserve the trees has nearly reached its target of 1,000 signatures as of today (29 May), while over thirty people attended a meeting of concerned residents on Wednesday (27 May). Campaigner Deepa Shetty, who launched the petition, said: "Today people were using the pathway with buggies and prams with no issue. "We request an independent review for these 12 trees and proper consultation with a civil engineer to discuss pavement restructuring solutions." Amey operations manager for grounds and arboriculture Jeremy Willis said: "The highway has to meet standards according to the Highways Act and so for us to get them up to that standard, there are trees causing that damage which need to be removed�. "We can't not do anything about it – we have a legal responsibility." In 2012 the city embarked on a 25-year, PFI-funded highways maintenance project across the city, known as Streets Ahead.
Planting different shrub species for carbon uptake and pollution removal A. Fini1, J. Mori2, F. Ferrini1, G. Burchi2
CRA UnitĂ di ricerca per il vivaismo e la gestione del verde ambientale ed ornamentale (VIV) 2
CRA-VIV, Via dei Fiori 8, 51012, Pescia (PT), Italy
R
ising atmospheric CO2 concentration i s d r i vi n g a wh o l e set o f environmental modifications, known as climate change. Urban Forestry and urban greening has been reported to contribute effectively to CO2 uptake because: 1) trees and shrubs are planted inside or nearby the urban environment, where the concentration of CO2 and pollutants is higher; 2) they offer several benefits in situ, where they can be appreciated by over half of World population. CO2 is absorbed through the stomata, then it is assimilated in the photosynthetic process and stored as woody and non-woody biomass. In parallel to CO2 assimilation and carbon storage, urban green removes significant quantities of trace metals produced by
vehicular traffic and human activities (i.e. Cd, Cu, Zn, Pb, Ni). However, growing conditions of urban trees are different than those experienced in their natural environment, and several stressors can harm tree health and cause premature plant death; thereby reducing benefits of urban plants up to 90%. As a consequence to maximize the benefits of green areas, care must be taken in the selection of species. The impact of different tree species on carbon sequestration and air quality has been extensively studied in the last 15 years (Beckett et al., 2000; Nowak et al., 2002; Nowak and Crane, 2002; Pugh et al., 2012), while shrubs have been little considered. However, the effect of shrubs in carbon uptake and pollutant sequestration is significant. Studies aimed at identifying the shrubby species with the highest carbon assimilation rate and with the capacity to withstand the stressful condition of cities are required to increase sustainability of urban areas. For these reasons our research group evaluated the ability of seven shrub species (Arbutus unedo, Elaeagnus x ebbingei, Laurus nobilis, Ligustrum japonicum, Photinia x fraseri, Viburnum l ucidum, Viburnum tinus ) to sequest er and store CO 2 in conditions of optimal substrate moisture (experiment 1); 2) and it tested the ability of the same shrub species to remove pollutants from the air (experiment 2).
Experiment 1: carbon uptake and storage under optimal water availability
“Elaeagnus x ebbingei had the highest carbon gain�
Elaeagnus x ebbingei had the highest carbon gain (both expressed on leaf area basis and of the whole plant) when grown under optimal water availability, mainly because of higher water use efficiency than the other species. Laurus nobilis ranked (Continued on page 48)
(Continued from page 47)
second for CO2 uptake, while photinia performed good on leaf area basis, but whole plant uptake was limited by lower leaf area if compared to other species. V. lucidum and V. tinus showed lower capacity of CO2 assimilat ion because of limit ed photosynthetic potential, while lower leaf area resulted in limited carbon gain in L. japonicum and A. The amount unedo.
Experiment 2: leaf deposition of some pollutants
The relative ability to adsorb trace metal on leaf surface depended on both plant species and type of metal. Despite of some species with very hairy leaves (i.e. E. x ebbingei, L. nobilis) showing a larger overall content of pollutants adsorbed on the unit of pollutants of leaf surface area by the whole than other
absorbed canopy was significantly greater in E. x ebbingei
High carbon uptake does not necessarily translate in high longterm carbon storage, as not all assimilated carbon is used for growth. Conversely, some carbon is allocated to the secondary metabolism, for reserve production, or for reproduction. However, in this experiment conducted under optimal conditions, we found a good correlation between carbon uptake and growth rate, which confirms E. x ebbingei and L. nobilis as the best species for carbon sequestration among those investigated if resources are not limiting.
Finally, it must be considered that, for a given increase in plant biomass, species which invest more in leaves than in woody biomass, store carbon for a shorter period of time, particularly in the urban environment where shed leaves are artificially removed (Nowak et al., 2002). Carbon allocation to leaves was higher in V. lucidum than in the other species, while V. tinus, E. x ebbingei and L. japonicum displayed to lowest Callocation to leaves. In conclusion, under optimal water availability, Elaeagnus x ebbingei was the species showing the highest daily carbon uptake, the highest growth rate, and the highest allocation to woody biomass, which make this species a very promising shrub for carbon sequestration in well watered urban areas.
species, though not
statistically significant
effectiveness in trace metal adsorption varied largely depending on the pollutant considered. Deposition per unit leaf area of cadmium, nichel and zinc was not influenced by plant species. Deposition of copper per unit leaf area was greater in L. nobilis than in L. japonicum, P. x fraseri and V. lucidum, while E. x ebbingei and A. unedo showed an intermediate behavior. Deposition of lead per unit leaf area was higher in E. x ebbingei than P. x fraseri, L. nobilis, A. unedo, with V. lucidum and L. japonicum performing intermediately. The amount of pollutants absorbed by the whole canopy was significantly greater in E. x ebbingei than in the other species. In accordance with previous works, the larger leaf area of E. x ebbingei if compared to the other species probably determined this finding. In conclusion, growth rate and whole plant leaf area were more important than leaf anatomical characteristics in setting differences in leaf pollutants deposition across six shrub species. Therefore, species capable of a fast growth rate and of sustaining large leaf areas are better suited for trace metal removal from the air. In this experiment, E. x ebbingei outperformed the other species investigated.
“Arbutus unedo showed an intermediate behavior.�
References Conclusion The take-home message is that Elaeagnus x ebbingei was the best-performing species under optimal water availability and the most suitable species for removal of trace metal from the air near a heavily polluted road, because of faster growth rate, higher leaf area and high metal deposition per unit leaf area due to very hairy leaves. We are aware that only a limited number of species was tested here, therefore other
studies should be
carried
out
for
the
evaluation of CO2 uptake potential of shrubs. Therefore, this study is not willing to stimulate extensive planting of E. x ebbingei or P. x fraseri monoculture, but it may offer for the first time a useful insight of CO2 assimilation potential of widely used shrubs in urban green areas.
Beckett, K.P., Freer-Smith, P.H., Taylor, G., 2000. Particulate pollution capture by urban trees: effects of species and windspeed. Global Change Biology, 6: 995-1003. Nowak, D.J., Stevens, J.C., Sisinni, S.M., Luley, C.J., 2002. Effects of urban tree management and species selection on atmospheric carbon dioxide. Journal of Arboriculture, 28(3):113122. Nowak, D.J., Crane, D.E., Stevens, J.C., 2006. Air pollution removal by urban trees and shrubs in the United States. Urban Forestry and Urban Greening, 4: 115-123. Percival GC, 2005. The use of chlorophyll fluorescence to identify chemical and environmental stress in leaf tissue of three oak (Quercus) species. Journal of Arboriculture, 31(5): 215-227. Pugh, T.A.M., MacKenzie, A.R., Whyatt, J.D., Hewitt, C.N., 2012. Effectiveness of green infrastructure for improvement of air quality in urban street canyons. Environmental Science and Technology, 46(14): 7692-7699.
Please click on the image (left) to be taken to the current edition of “CityTrees” the bi-monthly publication of the SMA, the MTOA’s sister organization in the continental US.
Another one bites the dust. Long serving Woodlands officer for Coventry, Tim Rose, retires. Read more
Advertising in the Axe, members go free! We publish four issues a year in full colour: Summer 2015
17th May (copy deadline 1st May)
Autumn: 2015
13th August (copy deadline 1st August)
Winter: 2015
14th November (copy deadline 1st November)
If you are looking to advertise then please see the rates below. If you are a member and wish to place a job advert then this can usually be accommodated free of charge contact the Editor straight away. Back page:
£250
Inside covers:
£200
Full page:
£175
Half page:
£100
Quarter page:
£50
If booking a run of four full page adverts in consecutive issues, then you will receive the final advert in the 4th edition for free. Advertisers who pay for ads in advance (by the publication of the first edition the advert runs in) receive an additional 5% discount. Payments received after that date will not qualify for the prepayment discount.
And finally.
“I’m late, I’m late “ were the immortal words of the rabbit that I seem to relate to more and more, but at least the rabbit had somewhere to go and an end to his lateness, my deadlines seem to run in an endless circle.
Wardens AGM about training for Tree Wardens, a subject close to my heart and something I pushed when I was still in LA harness. It was great to see that the Tree Officers in Coventry are embracing this and I was genuinely pleased to be involved in what I think will be the future direction for many Council's.
However, what I didn’t know was that the Tree Wardens had invited along one of Coventry City Councils (CCC’s) longest serving Arboriculturalists, Tim Rose (pictured left) who had very This must seem very germane to recently retired after a gazillion many of you Municipal Arborists years in service and they had who are vainly trying to make planned a surprise presentation to deadlines with half the staff and him to say thanks for all his half the resources you had just a support for the Tree Wardens and couple of years (or less) ago. So, service in the cause of the local like the rabbits tea party, is there woodlands. As you can see from an end to it all and is that end just the picture, Tim didn’t get a a mad meeting around a table clock, he got a limited edition with a group of characters that print of one of Coventry’s more are clearly insane? famous trees.
we actually serve, the residents and visitors to our “patch” The CCC Tree Warden network is only about a year and a half old and already has a warden for every ward and over 80 wardens in total. How does an LA tree officer make such and impression on a large group of residents in such a small time. Tim cared, it is a simple as that, well maybe not so simple as he had an unequalled knowledge of trees and woodlands and especially those in Coventry and he was described as “irreplaceable” by Tim Wetherhill. The CCC managing arborist. In times such as these when we are face un-paralleled cuts, losing such a resource permanently is a major problem, as CCC were making a saving and not replacing the post, a familiar story.
Well maybe not, as the Tree Wardens have encouraged Tim to help out from time to time, and I do not profess to have the Why would this make an answer but maybe it is time to re- impression on me, and moreover the truth is that unshackled from think what it is we do when trying why should it make an impression the politics of LA he can probably be more effective than ever in a to manage the Council’s tree on you? Read on. tenth of the time. stock, and yes, I have banged this Many of us are only “lucky” particular drum before. enough to get a sad speech from If there is an in-house future for LA tree management than it surely A couple of months back I was our line manger and some book has to be via community delighted to have been invited to tokens when we leave or retire, speak at the Coventry Tree and never a word from the people engagement on a meaningful level.
If you are reading this edition of the Axe on PDF then please ensure you have the view option set for a two page spread, it is designed for on-line viewing so make use of the links embedded. The MTOA is a fully constituted not for profit organisation . The views expressed in the magazine may not reflect the official views of the MTOA and the association accepts no liability for any views or technical advice presented by its contributing authors.
Ian McDermott
Editor