Conference Preview Part 1

Abstract

Urban trees play an important role in human society, by providing a range of ecosystem service benefits. Ecosystem services are defined as the direct and indirect contributions of ecosystems to human wellbeing, for example, carbon sequestration, pollutant adsorption, and stormwater runoff interception. The amounts of these so-called ‘regulating services’ are positively correlated to leaf area, and so large trees with large total leaf areas will produce greater benefits. However, it is common for urban trees to be pruned to meet modern requirements set by the electricity generation provider, wherein branches are removed to achieve statutory clearances between trees and the overhead utility wires, to prevent outages and faults in the electrical network. This sort of pruning can remove considerable proportions of live foliage.

Using iTree Eco, this research investigated whether utility wire pruning affected ecosystem service benefits for three regulating services (carbon sequestration, pollutant adsorption, and runoff interception). The 25 most common urban street trees in Auckland, New Zealand, were ascertained by examining a record of 10,323 tree records held in our database. A further 15 trees selected by Auckland Council’s urban forest manager were added to the list making a total of 40 urban trees. Mean mature dimensions (trunk diameter at 1.4 m, height, and crown spread) and standard deviations were ascertained for each species and 100 representative trees for each species were simulated with a normal distribution for each dimension in each species. Trees were stratified into small, medium, and large trees, being trees with a mean mature height of < 5 m, 5 m-10 m, and > 10 m, respectively. Two simulated utility wire pruning treatments were then established, being an L-shaped treatment, and a topped treatment, where an elliptical segment was removed from the latter, and half the elliptical segment was removed from the former. The percentage loss of crown volume for each tree was computed based on the two pruning treatments and the data were entered into iTree Eco for analysis of ecosystem services.

Utility wire pruning significantly reduced ecosystem service provision in large trees at p ≤ 0.05, but not in small or medium trees. Large trees that had been topped ($26.68) had significantly fewer total annual benefits than control ($46.11) and L-shaped trees ($36.97). The effect of tree size on ecosystem services was significant for all treatments. Large control trees had significantly greater ecosystem services than small control trees for all ecosystem services. Large control trees had significantly greater ecosystem services than small and medium trees for all ecosystem services. The differences in ecosystem service provision between trees in different size classes and between different treatments can be explained by differences in leaf area. Interestingly, large, topped trees still had significantly greater total ecosystem service benefits than small unpruned control trees. Local communities can still receive greater ecosystem service benefits by planting large trees that require ongoing utility wire pruning at maturity, than from small trees that do not.

Abstract

Trees of National Special Interest are those which – because of their age, size, condition, associated species, rarity, heritage or cultural value as individuals or collections of trees – have qualities of such significance that they differentiate them from most trees of the same species. Some trees are particularly valuable because they have multiple national values, e.g. King John’s Oak – a very large-girthed, open-crowned, ancient oak with a unique historic name which is host to at least one extremely rare decay fungus.

Across Europe there are interesting distributions of autochthonous species of ancient trees such as yews, oaks and beech. The distribution of such tree species, and especially old-growth remnants at the limit of their range, gives us insights into the way changing conditions across the continent are affecting their associated biodiversity and their adaptation to changing climate. This information should help us in assessing the risks to our current trees and what we should do in the future.

The UK has a long history of famous plant hunters who over several centuries have brought back tree and shrub species from across the world. Many trees have been introduced since the 16th century and the oldest ones are now up to 400 years old. Some of these are closely related by genus to other indigenous species but others are completely different. In some cases trees in the UK are perhaps the last remaining specimens of species that are under extinction threat in their home ranges. How such trees adapt to the conditions in the British Isles gives us insights into their tolerance to entirely different circumstances and how they may provide useful alternatives to our native trees if they cannot adapt to the changes that are forecast.

All of our Trees of National Special Interest have lived lives which should be of great interest to arboriculture and society.

Abstract

This presentation will consider recent court cases where trees have failed and look behind the scenes at the role of a tree expert in the legal process where a claim for injury or damage has been made against the tree owner – from examining a fallen tree, to cross-examination and legal judgments.

For many, the role of an ‘expert witness’ is shrouded in mystery, but Martin will lift the lid on the process of gathering data, forming an opinion, being challenged by a barrister, preparation of a joint statement with the opponent’s expert, and cross-examination in court. He will then set out some of the legal principles that have been determined by the courts in tree-failure judgments and consider a number of recent cases (including Hoyle v Hampshire County Council and others), offering an opinion on what they tell us about the law (and published guidance), and how they might influence attitudes to tree-safety inspections and liability.

Abstract

Planning for emerald ash borer (EAB) is a first and important step rather than dwelling in the EAB financial blues. Since EAB is on your doorstep in the UK, this talk will set out what we have learned to date with emerald ash borer management in North America. Since it was discovered in 2002 in North America, several ways to manage the insect have been developed that are both effective and economically efficient. Urban forestry management approaches for EAB management include economic analysis, treatment, tree risk assessment, and other strategies to shift the blues back to keeping the green in your urban forest. Learn how to estimate the costs and net benefits associated with pre-emptive removal, post-mortem removal, and treatments. Learn the implications of long-term tree injections and how ash trees respond to wounding. We will present studies using external wounding and internal discolouration associated with wounding with tree injection.

This talk will also further present the financial impact of emerald ash borer on municipal forestry budgets. Our research team was the first to test the net present value of EAB management options.

We also discovered three distinct phases were evident: an initial time period of 0 to 4 years (little budget change), years 5 to 8 time period (rapid budget increase), and years 9 to 12 (rapid budget decrease) after EAB was confirmed. Financial impacts on budgets will be set out and the effects on urban forestry activity (removal, pruning, education, safety training, tree planting) budgets further discussed. Research we conducted from the City of Milwaukee and the loss of ecological values of tree populations will be conveyed. Ultimately, the audience will learn how to plan now to make the impact of EAB on tree populations as painless as possible.