Colak

THE IMPORTANCE OF LIGNOTUBERS IN ARID-ZONE AND HUMID-ZONE ECOSYSTEMS WITH PARTICULAR REFERENCE TO RHODODENDRON PONTICUM L.

Alper H. Çolak¹, Ian D. Rotherham² and Wolfgang Spethmann³

Summary
Lignotubers generally occur in certain plant species which are typical of arid ecosystems in Mediterranean climate regions and have periodic fires. It is as yet unknown whether plants in more humid ecosystems have lignotubers. However, observations such as that some individuals of Rhododendron ponticum (which has natural distribution in the humid area of northern Turkey as well as in Iberia) typically have lignotubers suggest that they may be more widely spread. This paper presents a comparative study of lignotuber characteristics in species found in two contrasting ecosystems.
  R. ponticum is increasingly a species of large shrub familiar to arboriculturists and foresters working in both rural and urban situations in designed landscapes and in more natural wooded areas. Understanding the strategies and adaptation which enable the plant to be so competitive and so successful is therefore of interest to both the conservation professional and those responsible for trees.

Keywords: Lignotuber, re-sprout, Rhododendron ponticum

Hart

Effective Construction Method Statements and Tree Retention

Keiron Hart*

Summary
Construction activity places pressure on retained trees. This pressure generally comes in the form of modifications of the soil environment. This can result in the direct loss of roots, or changes to the soil profile resulting in a decline in the quality of the root environment. BS5837:2005 recommendations for Trees in Relation to Construction, provides a framework for the integration of trees into the built environment. Circular 11/95 allows for Local Planning Authorities (LPA) to secure additional information by use of appropriate planning conditions. Increasingly, tree officers are requesting detailed Method Statements where they believe pressures may be placed on trees. A review has identified that there is little consistency to the content of these documents. There is often a lack of consistency from LPAs as to what circumstances will stimulate a requirement for a Method Statement. There is also a lack of consistency as to when they are required within the planning timeline. Effective Method Statements will primarily cover appropriate health & safety issues, placing planned operations within the context of measures to limit risks to employees and any impacts to retained trees. For larger construction projects, early consideration allows inclusion within the build contract. LPAs generally do not deploy proactive enforcement resources for ensuring on site adherence of approved Method Statements.

Keywords: Health & Safety; Site Specific; Skeleton; Planning Condition; Project Manager

Hollis

CAN TREES BE DEPRECIATED LIKE (MECHANICAL) PLANT? A DEPRECIATED REPLACEMENT COST SOLUTION TO THE ADJUSTED TRUNK FORMULA ANOMALY IN CTLA’S TRUNK FORMULA METHOD

Adam Hollis

Abstract
A tree cannot be depreciated like mechanical plant, because as a living organism, it will grow and increase in amenity value for most of its life. In appraisal terms though, the rate of return on a tree’s increasing replacement cost will depreciate over time, as that nominal value disproportionately accelerates away from fair value. At issue, is the rectification of an accounting problem within the Council of Tree & Landscape Appraisers (CTLA) methods (making allowance for all changes in real value over time), rather than the undeniable value of aging trees. The full ecological and cultural value of ancient trees may be better considered under an alternative income approach to value, since their benefits may be partly unique and irreplaceable. Nonetheless, CTLA methods (which may be better suited to more regular urban forestry applications) will continue to provide a robust indication of their general worth. With regard to the Trunk Formula Method (TFM) of amenity tree valuation, this paper proposes an alternative procedure to that of the Adjusted Trunk Area Formula (ATAF) in consideration of large trees (>750mm stem diameter) and their replacement costs and end values. The ATAF seeks to regulate the accelerating cost of replacing larger diameter trees, by applying a quadratic equation to their area increments. The proposed alternative will be more consistent with appraisal standards: adjustments are no longer made to the cost metric, but are instead encompassed within the depreciation process by assessing the comparative age of a tree, as well as its current condition. Such a broader definition of an asset’s physical deterioration is in keeping with standard appraisal practice.

British Standards and Arboriculture

Mick Boddy

Summary
The British Standards Institution (BSI) is the UK National Standards Body. A brief overview of its activities and how British Standards are developed is given, and the scope, constitution and work of the B/213 – Trees Technical Committee explained. The current status of the three existing standards for which the B/213 Committee are responsible is summarised, and the development and issues relating to the proposed standard on tree safety inspection, BS 8516, considered.

Can a More Disciplined Approach to Tree Appraisal Inform Development Site Surveys and Tree Preservation Decisions – and Vice Versa?

Adam Hollis

Summary
Some of the benefits gained from applying a rigour of process to tree valuation could be exported to wider forms of tree appraisal in the UK, such as development site surveys. Indeed, surveyors may already use depreciation methods intuitively, but unconsciously, on development sites. The advantage of unconscious usage is that practitioners have a pre-existing familiarity with these broader appraisal methods; the disadvantage of unconscious practice is that the process remains unfocussed and lacking in internal coherence – no ‘grammar’ of process. Alignment with more universal methods of quality categorisation than those currently employed in UK practice (i.e. British Standard 5837: 2005 Trees in relation to construction), could lead to a greater transparency of process and greater consistency in consultants’ reports. Cross-fertilisation with more disciplined appraisal techniques, such as CTLA’s Trunk Formula Method (TFM), is proposed, rather than straight substitution by them. A full TFM appraisal may be too detailed an exercise for each individual tree on a development site; nor is the financial valuation of each tree proposed. Rather, the proposal is that the TFM depreciation factors (Species, Condition, Location) inform the future review of BS5837’s quality categorisation process, imparting to it, the basic grammar that is currently lacking. Tree officers could also develop this grammar to more readily justify Tree Preservation Order designations, beyond essentially visual criteria, and through the addition of the monetary factors, when seeking high-level fines. Despite 40 years of amenity tree valuation in the UK, arboriculturalists remain singularly unversed in the broader appraisal language. Familiarisation with and adaptation of CTLA methods, which draw upon this grammar, could help expose arboriculturalists to the language and allow them to communicate valuations more universally to the other professions and industries to which arboriculture must increasingly relate.

Green Infrastructure: The Strategic Role of Trees, Woodlands and Forestry

John Lockhart

Summary
Green infrastructure is a term that many of us will no doubt have heard of, in that it has become much more common currency in relation to new policy and proposals within the planning and development field within the last five years.

But what is green infrastructure?

What is its role within the planning system?

Is it relevant to ourselves as tree and woodland practitioners?

How can green infrastructure be delivered and how can we be involved in the process?

This paper sets out to answer these questions, setting out both the policy context and bringing practitioners up to date with the way in which the policy is being brought forward and led by the development within Growth Areas and emerging New Growth Points. It will help to re-emphasise the importance of trees and woodland with particular reference to their green infrastructure function and it will provide guidance as to how we as practitioners should engage with the emerging policy. It will explore how we may be able to assist in the delivery of green infrastructure as a critical element of our urban and peri-urban environments going into the future.

A Technique to Help Arboriculturists understand the Sequential Nature of Tree Introductions into Historic Landscapes

Clive Mayhew

Summary
Professional arboriculturists are well trained and practiced in the scrutiny of trees. However, the character and execution of that training frequently results in trees being examined as individual units within the landscape. This paper suggests that arboriculturists are less well equipped to understand the collective significance and interrelationship of trees in historic landscapes. It also introduces a technique by which arboriculturists might gain a greater understanding of such landscapes and consequently inform their management decisions upon them.

Schubert (1)

The objective of the in vitro studies was to identify a Trichoderma strain with a high antagonistic potential against the basidiomycetes Ganoderma adspersum, Ganoderma lipsiense, Inonotus hispidus, Polyporus squamosus and the ascomycete Kretzschmaria deusta. For this purpose dual culture and interaction tests in wood blocks as well as investigations on fungal growth and germination behavior of conidia under different conditions were performed. Hyphal interactions were observed by scanning electron microscopy (SEM). The effect of Trichoderma spp. on wood colonization and degradation of wood decay fungi were quantitatively analyzed by means of dry weight loss measurements of wood and qualitatively by histological studies. The different Trichoderma species all showed an antagonistic potential against wood decay fungi in the in vitro studies. However, significant differences between the species and strains were found (P<0.001). Trichoderma atroviride (T-15603.1) showed the highest competitive activity against most wood decay fungi. An influence of physical and chemical parameters, in particular temperature and water potential on growth and germination behavior of conidia was evident. The species of wood decay fungi showed significant differences in their sensitivity when challenged by Trichoderma. Polyporus squamosus showed an extensive resistance in most laboratory tests indicating that target specificity of the antagonist needs consideration.

Schubert (2)

Field experiments were carried out at different locations and on hosts with T-15603.1, a Trichoderma strain for biological control of wood decay fungi. The objective of the studies was to monitor and optimize conditions for colonization of the antagonist, its survival in time and space and to improve its effectiveness as wound treatment method. A total of 159 angiosperm trees and 1431 wounds from six different species (Platanus x hispanica, Acer pseudoplatanus, Tilia platyphyllos, Populus nigra, Quercus rubra, Robinia pseudoacacia) were treated with different conidial suspensions of T-15603.1. In comparison to untreated control wounds, T-15603.1 significantly suppressed growth (82.3%) of wounds colonised by three basidiomycetes Ganoderma adspersum, Inonotus hispidus and Polyporus squamosus (P<0.001). Monitoring results with RAPD-PCR showed that spore suspensions applied in a humidity storing gel as a carrier suspension significantly increased the germination rate and therefore colonization of the wound surface by T-15603.1 (P<0.001). Interpretation and characterization of the isolated microorganisms such as diversity and succession were analyzed using diversity indices. The results demonstrate that T-15603.1 can be successfully applied as a biological wound treatment against wood decay fungi of urban trees.

Packham

Dating back to the time of the Raj, when Schlich was Inspector-General of the Forests of India (and a Knight Commander of the Indian Empire), this book embodies a vast amount of information and virtually summarizes good practice at the time when the author was Professor of Forestry at Oxford. I picked up my copy in Foyles bookshop around 1960, noting the signature in the front of Alfred G. Borman (Junior) 1927, which itself augured well. Its contents, which explain in great detail what a forester has to do, from surveying a fresh site, installing efficient drainage, planting the young trees and finally felling them in a well-designed sequence, are divided into four parts. The first is ‘The Foundations of Silviculture’ which commences with the atmosphere, climate, soil, the quality of localities and the effect of forest vegetation upon them, the development of forest trees and the measurement of their various features. The duration of life and reproductive power of trees are also described. The lack of adequately described soil profiles is a striking difference from modern texts, although the soil descriptions given must have been good enough for contemporary foresters at the time. In contrast, the section on the character and composition of pure and mixed woods, which includes an analysis of the uses of shade bearing and light demanding species, remains sound. Part I concludes with a review of silvicultural systems, which are well described and very effectively illustrated.

Mattheck

Franz Gruber has questioned the validity of all VTA-failure criteria in the German Journal “Agrar- und Umweltrecht” in 2007 to which we responded. All debates can be read in German language in: www.arboristik.de Now the Arboricultural Journal (Volume 31, Number 1, April 2008) imported Gruber’s criticism of VTA to England. Because this is nearly identical to the German versions, here only a set of explanatory figures is used to show that Gruber’s ideas are in our opinion both illogical and incorrect.

Gruber

It is well-known that trees can fail under natural loads. This can happen, for example, for healthy full-crowned and unhealthy crown-thinned trees, for not slender and for slender trees, for non hollow and for hollow trees, for deep-rooting and for flat rooting trees, for slender not hollow and for slender hollow trees, for not slender not hollow and for not slender hollow trees. But trees do only fail if the loads (internal + external) exceed the individual marginal tree strength (marginal loading capacity, stability: anchorage, bending strength). If I do not define a critical load I cannot define a critical morphological failure criterion. If I define an individual failure criterion I have to define the individual critical loading capacity (marginal loads).
  Complex multi-factor dependant natural processes like tree stem breakage or tree throw uprooting normally cannot be explained satisfactorily by simple mono-factor (mono-parametric) records and monocausal developed rules of thumb like VTA − t/R = 0.32, H/D = 50, l/ D = 40 and Rw/R-root radius curve of only failed trees. This is, from the beginning, an impossible experiment, being scientifically unsuitable and with insufficient empiric field studies (see gruber, 2007e) and would be comparable to solving a mathematical equation with many unknown variables by using only one known parameter (compare formulae a, b).

Colak

Summary
This paper describes stand structure and growth in natural oriental beech forests of northern Turkey. All sample plots showed uneven-aged stand structure at 0.01 significance levels. This was confirmed by Z-test results where Z_min: 1.58 and Z_max: 33.30 values were determined. The total volume of uneven-aged oriental beech stands ranged between 289.8-1481.9m³/ha in pure stands, and 172.2-924.2m³/ha in mixed stands, giving a mean volume for all stands of 500m³/ha. Correlation and regression analyses were carried out to test site indexes, and typical increase of stand volumes in line with site indexes were established (F= 118.452 ^*** > F_{0.001; 1; 83} = 11.7439). Stand volume and its distribution into diameter classes in site indexes (F= 409.78 ^*** > F_{0.001; 5; 1372} = 3.743) was highly significant. The acquired basal area values ranged between 91.6-17.4 (42.9)m²/ha and stand volume ranged between 3.8-23.4 (11.8)m³/ha/year. This study into oriental beech forests, may guide managers in Turkey, in south-eastern Europe, the northern Caucasus, northern Iran and Syria. The implications of the results for forest management are discussed.

Keywords: Uneven-aged forest, oriental beech, forest management

Helliwell

Abstract
Methods for the valuation of visual amenity are very briefly discussed, including the possible relevance of using costs as a basis for calculating values. Other amenity values which may be derived from trees and woodlands, such as shelter, shade, biodiversity, pollution control, and flood alleviation are also briefly considered. The basis for the Helliwell System for the visual amenity valuation of trees and woodlands is then described, and comparison made with other methods, including the Council of Tree and Landscape Appraisers (CTLA) approach. Current thoughts on the way forward for such methods are outlined.

Holding

Summary
Increment core samples taken from the main stem of cedar tree (Cedrus sp) showed unusual ring width sequences that could not be explained from detailed microscopic analysis.
  A full trunk disc was obtained and the ring patterns investigated. The occurrence of false and locally absent rings was determined and the rings dated. The beginning of the unusual ring width sequences coincided with development of the land around the trees for housing in the late 1970s. Root damage and/or changes in the rhizosphere associated with the housing development are likely to have been responsible for the period of abnormally slow and erratic growth of the tree. Despite a near twenty-year period of slow and erratic growth the tree had returned to a reasonable, consistent and regular growth ring width sequence by the late 1990s.
  Caution should be exercised when undertaking ring counts and interpreting ring widths using increment core samples taken from trees that may have suffered traumas as a result of root or soil damage or from the trunks of trees directly below large pruning wounds or lost branches. Similar caution should be exercised when interpreting increment core samples showing unusual resin ducts (cedars and some other conifers) or erratic ring widths.

Mattheck

Summary
The failure of a hollow tree can cause severe damage to goods and even people. Therefore the understanding of failure modes and failure criteria of hollow trees is of high relevance. In this paper the VTA (Visual Tree Assessment) failure criteria are compared to the failure criteria of people who test trees by pulling them with a rope or use the SIA-method for assessment which has already been critically described by the authors for other reasons (MATTHECK and BETHGE, 2005). The method is now known under the label “Statics Integrated Assessment” or in German SIB (Statisch Integrierte Baumbeurteilung).

Packham

Summary

1. Study of annual production of beech mast at twelve main sites including closed canopy beechwood, shelter belts, avenues and an isolated tree in a park, as well as intermittent observations at others, has now continued for twenty-eight years.
2. During this period beech mast was sampled from up to 100 trees by seven-minute samples collected from the ground. Aerial samples have also been collected from low-growing branches.
3. Production of full seed varies greatly from year to year, and all trees produce empty pericarps as well as full mast, especially on lower or shaded branches.
4. The proportion of full nuts consumed or damaged by the moth Cydia fagiglandana Z., birds and small mammals, in English sites, can become significant especially in non-mast years.
5. Good masting occurred in 1980, 1982, 1984, 1987, 1990, 1995, 1997, 2000, 2002, 2004 and 2006: after each of these good years, one year of very poor masting normally followed. The best year recorded so far was 1990. In both 1981 and 2005, no full mast was found, and singularly very little in 1991 and 2001.
6. Regional variation within England is much less than the annual variation, but over the period the northern trees have produced on average fewer full nuts but rather more empty and total nuts. In 2007, however, northern trees produced markedly less full and total nuts than their southern counterparts.
7. Over such a long period it was inevitable that site changes would occur. In some instances the substrate beneath particular trees is now less favourable for rapid nut collection. As some trees have died, additional younger trees are now being assessed. In 1996, far more viable seed was formed in certain Scottish sites than at those we observed in England, so it is highly desirable that Scottish and Welsh sites be monitored in the future.

Keywords: Cydia fagiglandana, Fagus sylvatica, beech mast sampling, masting, long-term ecological survey*

TREES AND PAVEMENTS – ARE THEY COMPATIBLE?

Stephen M. Blunt

Summary
Research into the interaction of tree roots and the conditions beneath our pavements, particularly soil materials and compaction, has been carried out for Transport for London. The programme included work to allow pavement specifications to be interpreted in terms familiar to arboriculturists, work to express the requirements of trees in terms familiar to highway engineers, work to examine the performance of roots in compacted substrates including soils and construction materials, and work to establish how much water a mature tree requires from the root zone. The objective of this work, carried out between 1999 and 2002, was to contribute to new planting:paving systems which allow trees of large stature to flourish in our urban centres. This paper describes the work and the results achieved, updating an earlier paper presented in 2000 (BLUNT, 2001).

LIGHTNING PROTECTION AND TREES

Ben Fuest

Introduction
This research was established for the purpose of developing a better understanding of lightning protection systems specifically designed to be fitted to trees. Coming from a background in sylviculture my initial concern was to enable important and intrinsically valuable trees to be protected from damage resulting from lightning strikes. However it quickly became apparent that the protection of nearby structures and buildings that might be liable to collateral damage in the event of strike was of equal significance.
  Research showed that on those occasions where lightning protection had been installed in trees, the system employed had been based upon designs originally intended for use on buildings and other essentially non-dynamic man made structures. The particular problems of installing the necessary hardware into living and growing trees did not appear to have been adequately addressed. Thus the direct effect on the tree of the installation of the required hardware is not factored in, with the result that trees are likely to be caused some degree of long-term harm in the very process of attempting to protect them.

CONFISCATION AND DELIBERATE DESTRUCTION OF OLIVE TREES IN THE WEST BANK AND GAZA AND THE EFFECT OF THIS ON THE PALESTINIAN ECONOMY

J. Hughes

Summary
The olive tree industry in Palestine is one of the unseen casualties of the conflict in the region. As the economic grip tightens on the people, agriculture is becoming more important. Men and women who travelled into Israel or surrounding countries for employment are now confined close to home because of the restrictions in movement imposed on them by an 8m high separation barrier and by the dozens of checkpoints that are now part of everyday life. These same obstructions are also one of the challenges facing the farmer in the struggle to maintain his trees, harvest and market his product. As with farmers in the rest of the world, the only resource that he has is his land and he will not leave it. The farmers are adapting to the new situation by tapping new markets in Fair Trade and speciality produce. This paper outlines some of the obstacles that have been put in their path.

THE PLACE OF TREES IN THE CITY OF THE FUTURE

Alan Simson

Abstract
Many towns and cities in the UK and on mainland Europe are at a point in the urban system life cycle when they have shifted from an industrial to a post-industrial economy, and are entering a cycle of decline. In an attempt to reverse this trend, a frenzy of ‘urban regeneration’ has broken out to try to seek new sources of prosperity to replace those that have disappeared. This is not, however, a new activity. A similar frenzy accompanied the last period of rapid urban expansion in the UK in the nineteenth century when, in order to confront rapid social, economic, cultural and environmental change, programmes of ‘urban greening’ were established, including the first public parks and the advent of street trees.
  This paper suggests that in the current frenzy of post-industrial urbanism, many of the lessons learned in the nineteenth century have yet to be re-learned and up-dated for the twenty-first century, and that urban forestry/arboriculture has the potential to play a far greater role in this that it currently does.

Keywords: urban forestry, post-industrial cities, urbanisation, arborists, trees.

SHOOT DIEBACK IN CLIPPED YOUNG GOLDEN LEYLAND (CUPRESSOCYPARIS LEYLANDII) TREES – A PHYSIOLOGICAL MECHANISM?

N. Taylor¹, R.W.F. Cameron1, T. Blanusa^1,2,*

Abstract
Shoot dieback is a problem in frequently trimmed Leyland hedges and is increasingly affecting gardeners’ choice of hedge trees, having a negative effect on a conifer nursery industry. Some damage can be attributed to the feeding by aphids, but it is unclear if there are also underlying physiological causes. In this study, we tested the hypothesis that shoot-clipping of conifer trees during adverse growing conditions (i.e. high air temperature and low soil moisture) could be leading to shoot ‘dieback’. Three-year-old Golden Leyland Cypress (x Cupressocyparis leylandii ‘Excalibur Gold’) plants were subjected to either a well-watered or droughted irrigation regime and placed in either a ‘hot’ (average day temperature = 40°C) or a ‘cool’ (average day temperature = 27°C) glasshouse compartment. Half of the plants from each glasshouse were clipped on Day 14 and again on Day 50. Measurements of soil moisture content (SMC), net CO₂ assimilation rate (A), stomatal conductance (g_s), branchlet xylem water potential (XWP), plant height and foliage colour were made. Within the clipped and unclipped treatments of both glasshouse compartments, plants from the droughted regime had significantly lower values for A, g_s and XWP than those from the well-watered regime. However, there was no difference in these parameters between the hot and cool glasshouse compartments. The trends seen for A, g_s and XWP of all treatments generally mirrored changes in SMC indicating a direct effect of water supply on these parameters. By the end of the experiment the overall foliage colour of plants from the hot glasshouse was darker than that of plants from the cool glasshouse and the overall foliage colour was also darker following shoot clipping. In general, shoot clipping led to increases in A, g_s XWP and SMC. This may be due to the reduction in total leaf area leading to a greater supply of water for the remaining leaves. No shoot ‘dieback’ was observed in any treatment in response to drought stress or shoot-clipping.

Keywords: Leyland cypress, conifer, drought, high air temperature, xylem water potential, soil moisture, stomatal conductance, CO₂ assimilation, plant height, foliage colour, shoot dieback, shoot clipping, pruning.

UNTENABLE FAILURE CRITERIA FOR TREES:
I.THE RESIDUAL WALL THICKNESS RULE

Franz Gruber*

Summary
The Visual Tree Assessment (VTA) rule t/R = 0.32, which has been described as a universal rule of tree safety for hollow trees with full crowns is scientifically insupportable and must be rejected. Many full crown trees with t/R ratios of more than 0.32 can be broken by loading from external sources, and trees with such ratios are not necessarily safe. It can be stated that the risk of stem failure will diminish with increasing thickness of sound wood, but stem failure is significantly dependent on the loading applied to the tree, and the 0.32 rule does not take this into account. Tree safety needs to be assessed individually rather than using general “mono-parametric” safety rules. There is little scientifically tested knowledge about the complex matter of tree safety, and it seems absolutely essential to carry out research, both fundamental and applied, into this subject.

Keywords: Tree failure, stem breakage, visual tree assessment (VTA), tree breakage, hollow tree, tree safety

BS 3998 RECOMMENDATIONS FOR TREE WORK;
LIKELY IMPLICATIONS OF THE NEXT EDITION

David Lonsdale

Introduction
The last edition of BS 3998 appeared in 1989 and has been followed by many innovations, not only in technology and in working practice, but also in the appreciation of the need for a clear method of deciding what type of tree work (if any) is required. There has, in particular, been a growing awareness of the value of trees for the wildlife habitats that they provide, both in life and in death. Also, there have been several changes in the law, which need to be taken into account in the next version of BS 3998.

ROOT SPACE UNDERNEATH TRAFFIC LANES

Klaus Schröder*

Summary
Tree roots need certain essential conditions for optimal growth. These include, for instance: enough space, enough ground air ventilation and moisture, sufficient amounts of macro- and micro-nutrients, as well as the existence of symbionts. However, these conditions are not always found at potential rooting zones for urban street trees. Rooting zones often lack space and the soil is often too compacted. Furthermore, the surface is sealed off with materials impermeable to water and air, thereby causing additional problems for growth.
   Additional problems arise if street trees are planted in narrow central strips between traffic lanes. The tree roots are stuck between the concrete kerbstones of the lanes on both sides and in such cases the soil often consists of highly-compressed building material through which tree roots cannot grow. These are some of the reasons why many trees that are planted in such places are in a very poor condition. Similar poor development of trees is observed when trees are planted in small planting pits in highly-compacted road beds or in poor soil. In the city of Osnabrück (Germany), officers responsible for trees and arboriculture and for road construction worked together to find solutions to these problems by using novel methods for the creation of additional rooting zones for trees. The structures underneath traffic lanes are referred to as Wurzelkanäle (Root Ducts) and Wurzelkammern (Root Chambers).

GREENING THE BLACK COUNTRY: THE WORK OF THE MIDLAND REAFFORESTING ASSOCIATION IN THE EARLY TWENTIETH CENTURY

Justin Webber

Summary
In the early twentieth century a pioneering organisation, concerned with regenerating degraded land through tree planting projects, was established in the Black Country under the name of the Midland Reafforesting Association. Pre-dating a range of organisations involved in facilitating new plantations on industrial wastelands such as the Land Restoration Trust and the Forestry Commission’s Woodland Research Unit, the Midland Reafforesting Association existed for over twenty years as the driving force behind afforrestation efforts in the rapidly urbanising West Midlands Conurbation. The ideas that stimulated the formation of the M.R.A. can largely be located within an expanding global forestry sector that was becoming both more professional and more academically rigorous. However, wider developments occurring in British forestry policy in the early twentieth century did not largely serve to help the M.R.A. on a practical level. This article will attempt to explain this apparent failure as well as assessing the wider development of the Association as a unique voluntary organisation concerned with promoting the planting of trees from its establishment in 1903 to its dissolution in 1925.

OVERVIEW OF THERMAL IMAGING FOR TREE ASSESSMENT

Alessandra Catena and Giorgio Catena *

Summary
The value of thermography for trees is reviewed in relation to the needs of inspectors and diagnosticians in the fields of forestry, arboriculture and veteran tree management. Images obtained with an infrared camera allow the early detection of various kinds of alteration in trees, including bark necrosis, decay and the onset of adaptive growth in response to damage or mechanical stress. Advantages include total non-invasiveness, rapidity of use, the provision of ‘real-time’ information and the ability to work at a distance of as much as 25 m. In order to assess trees, however, the surfaces must be out of direct sunlight, free from running water and unobscured. The images do not distinguish between different kinds of alteration automatically, but they can usually be correctly interpreted in the light of appropriate knowledge and experience. The technique does not allow a truly quantitative assessment of the relative extent of decayed and sound wood, but it appears to be accurate enough to identify trees which merit either remedial action or more precise assessment.

Keywords: Tree physiology, Tree assessment, Veteran trees management, Habitat assessment, Tree decay, Tree hazard assessment, Thermography, Thermal imaging, Infrared photography, Phytophthora spp.

TREES, DAYLIGHT AND BUILDINGS

Rodney Helliwell

Summary
Whether considering the effect of trees on the amount of light beneath single trees, groups of trees, or in nearby buildings, arboriculturists need to understand the nature of daylight and how it can be affected by the location, type, and management of trees. This paper attempts to set out very briefly the relevant features of daylight and to indicate ways in which trees and buildings might successfully co-exist.

THE TREE OWNER’S DUTY OF CARE AND DUTY OF INSPECTION

Richard Stead*

Summary
The precise duty of care of the tree owning landowner is difficult to state. The standard of inspection required is influenced by the higher standards of the arboricultural profession which may impose upon individual landowners unrealistic demands. This may lead to a defensive approach to tree management.

STREET TREES AND STORMWATER MANAGEMENT

V.R. Stovin,* A. Jorgensen,^† and A. Clayden^†

Abstract
Urban trees play an important role in the urban hydrological cycle. Yet little consideration has been given in the UK either to the increasing pressures that act to reduce urban tree cover or the opportunities that might be provided by land-use planning policies to increase it. Research in North America, particularly by American Forests (2007), suggests that urban tree cover may be directly equated to stormwater volumes and, therefore, to the costs of providing engineered structures for stormwater management. Tree planting policies have been justified on the financial benefits associated with their stormwater management function alone, notwithstanding the broader spectrum of benefits they provide within the urban environment.
  This paper presents preliminary research aimed at transferring these findings into a UK context. Two residential morphology units (RMUs) have been defined within the city of Sheffield, for which current levels of tree cover have been accurately quantified. Current tree cover levels are relatively low, but approaches to integrating more trees into these two landscape types are outlined.

Keywords: Green infrastructure, Hydrology, Interception, Rainfall, Runoff, Stormwater, Street Trees

NATIONAL TREE CONDITION SURVEYS: THEIR BENEFITS AND LIMITATIONS

David Lonsdale*

Summary
The reasons for conducting national tree surveys may include the following: concerns about the effects of human activities, the need for data as a tool for management or regulatory control, the need to provide early warnings of problems, provision of data for research and a desire for greater public awareness of trees. Specific studies and surveys exemplify the importance of deciding what sort of survey is required and of taking account of the limitations of surveys, as well as their benefits. Limiting factors include the following: the quality and consistency of data collection; the difficulty of establishing a ‘baseline’ of ‘normal’ or ‘healthy’ condition when monitoring trees; the inadequacy of relatively short-term surveys for recognising changes over time; a shortage of physical or financial resources. The value of data from casebook studies, compared with survey data, is discussed.

Keywords: tree survey, monitoring, surveillance; tree condition

THE MANAGEMENT OF MAJOR ARBORICULTURAL INCIDENTS*

Clive Mayhew

Abstract
This paper recalls the great storm of October 1987 which swept across southern Britain and reflects upon its legacy for arboricultural crisis management. It examines how the emergency services have developed their response to major incidents in the intervening years and makes suggestions as to how a current arboricultural reaction to a major emergency might be formulated.

Keywords: Emergency planning, arboricultural response, command structures.

THE INFLUENCE OF CARBOHYDRATES, NITROGEN FERTILISERS AND WATER-RETAINING POLYMER ROOT DIPS ON SURVIVAL AND GROWTH OF NEWLY TRANSPLANTED BARE-ROOTED SILVER BIRCH (BETULA PENDULA ROTH.) AND EUROPEAN BEECH (FAGUS SYLVATICA L.)

Glynn C. Percival¹ and Sally Barnes²

Summary
The influence of carbohydrates and slow release nitrogen fertilisers in combination with a water-retaining polymer applied as a dip to the root system of two transplant-sensitive tree species, silver birch (Betula pendula Roth.) and European beech (Fagus sylvatica L.) under field conditions was investigated. The efficacy of the treatment on growth was quantified by recording root and shoot growth and survival at weeks 8 and 24 after bud break. Improvements in tree vitality were assessed by measurement of leaf photosynthetic rates, chlorophyll fluorescence and chlorophyll content. Irrespective of species applications of a water-retaining polymer alone had no significant effect on tree survival rates or tree vitality. Results show that carbohydrates and nitrogen fertilisers singly and in mixtures when combined with a water-retaining polymer applied as a root dip at the time of planting can be used to reduce transplant losses and improve tree vitality and growth over a growing season in two difficult-to-transplant species. Although the magnitude of the response differed between species, in all cases where carbohydrates and nitrogen fertilisers were applied a decrease in the shoot:root ratio was recorded at week 8 and 24 post treatment indicating resource allocation in favour of root over leaf and shoot growth.

DANGEROUS TREES?

John Adams*

Abstract

This is a modified version of a paper prepared for a conference on The Future of Tree Risk Management, held in London on 15 September 2006.
Britain, in the view of former Prime Minister Blair, is “in danger of having a wholly disproportionate attitude to the risks we should expect to run as a normal part of life. … The result is a plethora of rules, guidelines, responses to ‘scandals’ of one nature or another that ends up having utterly perverse consequences.” My introduction to the world of tree risk management in Britain leads me to the conclusion that it is disproportionately risk averse and is having “utterly perverse consequences”.

THE EVOLUTION OF RISK ASSESSMENT AND RISK MANAGEMENT: A BACKGROUND TO THE DEVELOPMENT OF RISK PHILOSOPHY

David J. Ball*

Abstract

The usage of risk-based approaches can be traced back over millennia, but seemingly experienced surges during the era referred to as The Enlightenment in the 18th century and again at the close of the 20th century. The widespread application of risk-based thinking is thought by many to have yielded benefits, but across the spectrum of applications many controversies have been identified. Risk decision makers should be aware if not wary of the potential problems to which these controversies can give rise.

WHY RISK ASSESSMENT NEEDS AN UNDERPINNING PHILOSOPHY

David J. Ball*

Summary

Without a philosophy risk assessments cannot be interpreted and thus may be wrongly applied. The United Kingdom has evolved a sophisticated philosophy of decision making over two centuries although this is surprisingly little known outside of professional circles. This paper describes the philosophy and its connection with case law. It may also be possible to apply this philosophy to the issue of the level of risk assessment which is appropriate in given circumstances, for example, to arboriculture.

I’LL MANAGE RISK MY WAY

David J. Ball*

Summary

Those responsible for hazards have, under English law, a great deal of freedom to decide how to act, but with that freedom goes responsibility. The requirement is to do what is reasonable and not more than that. To achieve this duty holders need to be proactive, in touch with government thinking, aware of societal pressures and research, and to keep an eye on both day-to-day activities and strategic objectives, to prevent these from drifting apart. Various activities are suggested which can help bring this about.

TOWARDS A NATIONAL STANDARD FOR TREE RISK INSPECTIONS

Nick Eden*

Summary

The need for tree inspections for the purpose of safety assessments is justified in this paper by the author’s experience of being responsible for a tree that failed and caused a fatality. It also appears to be endorsed by a number of recent high profile cases. The need for standardised tree inspection and safety assessment methodology and associated training is presented as a result of the author’s experience in Court and a survey conducted by Lantra Awards in 2005. A description of two tree inspection and safety assessment training courses at basic and professional levels available from Lantra Awards is presented along with the steps they went through in the development process.
It is generally accepted that passing the examination that is part of the professional tree inspection course, is evidence of the competence of tree inspectors who make the final decision on tree safety issues.

MOVING THE FOCUS FROM TREE DEFECTS TO RATIONAL RISK MANAGEMENT – A PARADIGM SHIFT FOR TREE MANAGERS

Mike Ellison*

Summary

In the United Kingdom, the risk of death or serious harm from tree failure is extremely low yet the fear of litigation often results in a disproportionate allocation of resources to the survey, inspection and treatment of trees. Frequently, the presence of decay or defects will be cited to justify the removal and pruning of trees without adequate consideration of the often very limited risks associated with the condition.
By employing appropriate risk management techniques and by moving the initial focus away from tree defects and onto targets, tree managers can cost-effectively manage tree safety within the realms of reasonable practicability whilst optimising the multiple benefits conferred by the tree resource.

Keywords:

target · reasonable practicability · risk of significant harm · defect-led · expert

TOWARDS REASONABLE TREE RISK DECISION−MAKING?

Neville Fay*

Summary

While we are all continuously exposed to risks the legal expectation is that risks need not be removed but rather should be reasonably controlled. For tree risk management to be defendable, it is important to be able to review how risk decisions are made (how risks are identified, appraised and controlled). Though these activities form the basis of risk management, in the event of an accident, any relevant records may be used to establish whether duty of care has been met. Defendable risk regulation draws on industry guidelines and is specifically based on the presumption that the time, money and effort expended in meeting risk reduction should not be grossly disproportionate to the improvement in safety obtained.
When risks are of such a low order that they are regarded as insignificant they are considered ‘broadly acceptable’. A reasonable framework for risk decision-making would probably regard intervention to reduce broadly acceptable risks as unwarranted. Average annual tree-related deaths from structural failure in the UK are so few that, arguably, any expenditure targeted to avoid such risks might be considered unnecessary, given the limited benefit in risk reduction likely to be achieved. Yet, when harm arises from tree failure, those responsible for trees carry the weight of potential investigation by the police and the Health and Safety Executive, not to mention from civil litigation. When a tree-related death occurs a disproportionately high level of media interest tends to follow and sometimes this is also accompanied by a landmark legal case. While such circumstances are in some respects understandable (as rarity influences public interest), this can have an unreasonable influence on expectations of routine tree inspection standards, and expenditure on management, and, moreover, result in undesirable implications for the nation’s mature tree stock (loss of habitat, amenity, wilderness, carbon sink, etc.). To counter such defensive behaviour, an important role exists for the arboricultural industry – to work with other stakeholders to influence more rational outcomes. Such an initiative would make possible a more confident, defendable, professional stance for the benefit of sensible risk management policies and would contribute more widely to the long term sustainability of the nation’s trees and the ecosystem.

CURRENT ISSUES IN ARBORICULTURAL RISK ASSESSMENT AND MANAGEMENT

David Lonsdale*

Summary

People who own or manage trees are increasingly required to implement systems for assessing and managing risk. Fears which arise from a greater awareness of responsibility and of technical requirements can be allayed by the sense of confidence that a good system of tree risk management can provide. Both the tree inspection regime and its implementation need to be good, as shown by recent legal cases. Good practice is being aided not only by the application of risk assessment principles, but also by advances in technology. Advanced devices should, however, be used only when appropriate and when their users have the necessary competence and knowledge. The cost of managing risks from trees can be considerable, both financially and in terms of the loss of value provided by trees. It is therefore important to work towards an holistic evaluation in which trees and their associated risks are viewed alongside everyday things which carry both value and risk. To this end, arboriculturists need to engage with members of the risk analysis profession.

THE MANAGEMENT OF RISK WITH RESPECT TO CULTURAL HERITAGE – A CASE STUDY

John M. Watt*

Summary

Risk management at a strategic level operates to try to establish consensus in the face of uncertainty or conflict (or often both). Risks are taken in specific contexts, which relate to the aims and values of the organisation or society within which they operate. It is therefore crucial to identify the objectives of the organisation in order to identify and assess the things that threaten the achievement of these objectives (i.e. the risks). It is therefore wrong to define ‘risk management’ as managing human safety alone, which seems to have assumed an undue weight in some instances. A wider definition is:

"Risk: A situation or event in which something of human value (including humans themselves) has been put at stake and where the outcome is uncertain"(Rosa, 1998).

The concept of objective in risk taking is embedded in the human value part of the definition. We are only interested in risk where there is a decision to make because we (or somebody) desire a particular outcome. There are many desirable outcomes in tree risk management, only one of which is safety.

The care of cultural heritage objects represents an area where management of safety may conflict with management of the very things that people value in heritage – things that are ‘measured’ on very different scales, such as artistic integrity, patina of age or religious practice. While some of the things that threaten an object, such as air pollution, may be measured quantitatively, values are typically not so easy to capture in this way. This paper looks to the experience of heritage management to illuminate some of the challenges faced by strategic management of trees and to suggest ways that the benefits of trees may be brought more effectively into the debate on resource allocation for tree risk management. It suggests that defining ‘acceptable risk’, a central task of risk management, should not be based on safety issues alone.

PUTTING A VALUE ON TREES: AN ECONOMIST’S PERSPECTIVE

Colin Price

Summary

Economists try to put a monetary value on trees to aid rational decisions about scarce resources. Examples exist of all the eight general methods of valuing non−market products. All methods encounter problems, to do with what is valued, by whom, from what perspective; how subjectivity influences value, and how values are scaled or partitioned according to circumstance. For a value which is so context−sensitive, an appropriate valuation protocol involves expertise drawing upon more than one method: expert aesthetic judgement calibrated by reference to the relevant population; choice experiments to establish a cardinal scale of value; and reference to data on population preferences revealed in house purchase and travel decisions. A rough indicative valuation of amenity trees in the UK was £50,000,000,000 over a 100 year period.

Keywords:

environmental valuation, stated preference, revealed preference, subjectivity

PUTTING A VALUE ON TREES – CTLA GUIDANCE AND METHODS

Scott Cullen

Summary

Arboriculturists and urban foresters frequently need to put a monetary value on amenity trees. There is interest in the UK in exploring various alternatives to currently familiar valuation methods. This paper describes the basic concepts of amenity, value, valuation and amenity value to provide a conceptual framework for valuation and a well documented context within which consider one specific valuation alternative: the CTLA guidance and methods developed for amenity tree valuation in North America. The CTLA guidance and methods are grounded in generally accepted principles of professional valuation practice, rely on readily available data and are well developed and ready to use. A Regional Plant Appraisal Committee (UKI-RPAC) has introduced supplemental guidance for the region.

Keywords:

Amenity • Amenity Value • Appraisal • CTLA • Valuation • Value

HEALTH AND WELL−BEING IN WOODLANDS: A CASE STUDY OF THE CHOPWELL WOOD HEALTH PROJECT

Liz O’Brien and Hilary Snowdon

Summary

In recent debates concerned with increasing the physical and mental well−being of the British population, the natural environment has been put forward as a particularly suitable place for people to undertake a variety of physical activities. In Britain a range of projects and campaigns has been created by organisations such as the Forestry Commission, the Countryside Agency and English Nature (now Natural England), the Woodland Trust and the Royal Society for the Protection of Birds. These projects and campaigns have focused on encouraging and enabling people to use natural and green spaces for walking, cycling, tai chi and other activities. This paper describes the Chopwell Wood Health Project which was set up as a national pilot by the Forestry Commission to build an evidence base in relation to the use of woodlands for improving health and well−being. Chopwell Wood is located near to Gateshead in North East England. The evaluation of the project highlights the importance of the project leader and other individuals enthusing and enabling people to take part in the activities provided. The partnership developed for the Chopwell Project between the Forestry Commission, the health sector, and the local community played a key role in developing and delivering the work; specifically demonstrating the importance of effective partnerships. Recommendations highlight the need for concerted engagement with General Practices and health professionals; training of Forestry Commission rangers to be able to deliver health messages, and longitudinal evaluations that help to identify any long term benefits.

Keywords:

Health and well−being, woodlands, General Practitioner referral schemes, physical activity, restorative environments

DEFENCE REACTIONS AND FUNGAL COLONISATION IN FRAXINUS EXCELSIOR AND TILIA PLATYPHYLLOS AFTER STEM WOUNDING

F.W.M.R. Schwarze1, J. Grüner, M. Schubert and S. Fink

Summary

Twenty 15−year−old ash and lime trees were each wounded by creating a chainsaw cut and an increment borer hole in May 2005. After sixteen months, trees were felled, dissected and the axial extent of both wood discoloration and barrier zone formation associated with the wounds was greater in ash than in lime. Barrier zones extended only around part of the stem circumference in both species. In ash, the barrier zone consisted of 10−20 cell rows of axial parenchyma within the earlywood and a heterogeneous matrix of libriform fibres, small vessels and concentric bands of 5−40 cell rows axial parenchyma within the latewood. In lime, the barrier zone consisted of a homogeneous layer of axial and xylem ray parenchyma, in which the cell walls showed suberisation, a low cellulose content and few pits. Fungal culturing from the discoloured wood of both species yielded mainly deuteromycetes (Fungi Imperfecti). Only one basidiomycete, Polyporus squamosus, was consistently isolated. The evidently high decay−resistance features of the barrier zone of lime trees may enhance the trees ability to remain alive and intact, even when extensive decay develops within their central, poorly defended wood as a result of severe wounding. The results of the present study suggest a possible explanation why ‘wall 4’ i.e. a defensive layer that forms within the first annual growth ring after damage, is more effective in lime than in ash.