The future direction for arboriculture is clearly high on the agenda for everyone in the industry and September's event had the highest number of delegates ever at an AA conference.
First to arrive from JPA was director Jeremy Peirce, in time to hear the keynote speech from Lord Framlingham, one of the most high-profile figures in British arboriculture. A past AA president, he is also a fellow of the association and a registered consultant and is a keen supporter of Trees and Design Action Group (TDAG). He will no doubt be one of the most influential voices as urban trees and the environmental services they provide rise in political importance.
The morning session was chaired by chartered arboriculturist and independent scholar, Dr Mark Johnston. The presentations were given by experts from around the world and covered climate change and resilience, and the use of US software package ‘i-tree’ to demonstrate value and lead urban management practices. It was interesting to note the dramatic difference between US and UK local authorities in terms of resources: tree officers in this country can only dream of having teams of six or seven including a dedicated GIS specialist…
Tree health, biosecurity, disease control, tree inoculation and soil improvement were all covered in the afternoon, again by some of the world’s leading experts and academics.
Among these inspiring highlights, a memorable and sobering comment came later in the conference when one of the speakers, commenting on the state of urban tree planting, said that it was a sorry state when the measure of success with new tree planting was that they didn’t die.
Soils and SUDS
There were many standout moments from the second day for JPA consultant Chris Hawley. The Woodland Trust’s Jill Butler gave a presentation on the soil properties and organisms associated with ancient tree root systems and the implications for ancient/veteran tree conservation and management. Her illuminating talk highlighted the need for veteran trees to be better protected and recognised within the planning and legal framework.
Bob Bray, a landscape architect specialising in designing SUDS (sustainable urban drainage systems) projects, talked eloquently about utilising SUDS for arboricultural benefit, using techniques based on natural landscape features to manage urban water run-off in a holistic, creative way. He described how functional spaces could be created in schools, using SUDS both to irrigate trees and control pollution/litter.
He went on to say how careful species selection and design features can minimise maintenance issues in SUDS systems and how the urban landscape can be designed to manage water and provide functional, aesthetic and ecological benefits.
The highpoint of the afternoon session for Chris was US landscape architect and urban arboriculture and soils expert, James Urban, talking about structural soils, load bearing and engineering solutions for urban planting. He compared research data on the relative merits of different structural soils with cell systems containing loam soils.
He also emphasised the importance of urban trees’ access to sufficient soil volume and quality and how this can best be achieved. Trees, he said, are able to cope with surprisingly high concentrations of heavy metals, and hydrocarbon pollution can be held and remediated naturally over time within their root system.
Biomechanics and bananas
On the final day the morning session revolved around the central theme of tree biomechanics, with three outdoor masterclass workshops in the afternoon giving delegates – including JPA’s Dan Vickridge - some welcome fresh air.
Paul Muir, senior arboricultural consultant for Treework Environmental Practice in Bristol, kicked the day off with his keynote speech on ‘Safety factors versus strength loss: appropriate tree failure criteria’. He took the audience through the static load test, where the tension and compression are measured on a tree to determine if the trees is ‘stable’ or has a likelihood of failure in the event of a 50-year storm. The result? The early mature tree with few or no defects was more likely to fail than a fully mature/over mature/veteran tree, based on section modulus. In essence, when the crown has reached maximum proportions, or is in decline - yet there is still incremental growth on the main stem - the tree becomes less likely to fail.
Frank Rinn, founder of tree and wood analysis firm Rinntech, brought his entertaining but highly informative approach to the next session: ‘From wood anatomy to tree biomechanics and tree safety’. The most revealing thought for Dan was not the size of the decay within a tree stem but its location, and that compression wood will fail before tension wood as tension wood has a higher load-bearing capacity. With the rather surprising use of fruit to illustrate various forces and how they operate in different planes, delegates learned the easiest way to open a banana was to twist it! Another memorable fact from Rinn’s presentation: a reduction in the height of a tree will result in a decrease in wind loading of double that – for example, a 15 per cent reduction in height will reduce the wind loading by 30 per cent.
Forks and failures
Duncan Slater, senior lecturer in arboriculture at Myerscough College, talked about his six years of research for a doctorate in plant sciences, before moving onto the anatomy and mechanical behaviour of tree forks in Hazel. This provided a valuable insight into the complexities of fork anatomy with the interlocking fibres forming as strong a union as possible (although this can be compromised by bark inclusion).
Next was Dave Evans, principal consultant at The Arbor Centre in Bath, who brought his VALID (Vitality, Anatomy, Load, Identity, Defect) approach to the table for estimating likelihood of failure. This informed and interesting session showed how a more consistent answer was reached by arborists when using VALID in conjunction with QTRA (Quantified Tree Risk Assessment). Evans’ mnemonic can be used as part of QTRA but on its own also provides a neat tree inspection tick list.