At the beginning of June, Treework Environmental Practice (TEP) and The Royal Parks hosted a practical Soil Health & Tree Disease Workshop at Greenwich Park, focusing on soil assessment approaches to Sweet Chestnut Ink Disease and dieback. The event drew upon the knowledge and experience of leading organisations from within and outside the arboriculture sector. The Sustainable Soils Alliance, NIAB, De Rebus Plantarum (University of Padua) and SoilBioLab joined forces to stage and deliver a fascinating and innovative programme within the historic and picturesque London Park.
For many delegates this was their first insight into the relationship between soil health and tree disease, and there is a significant appetite for the knowledge shared by the experts on the day – as evidenced by the theme at this year’s Arboricultural Association conference in September: ‘Soils & Trees: Standing Your Ground’.
Expanding the boundaries of thinking and practice
Neville Fay, TEP Director/Principal Consultant and Fellow of the Linnean Society, said:
‘There is a distinct sector deficit in our knowledge and understanding of the relationships between soil and trees. By learning from experts beyond the normal confines of arboriculture we can expand the boundaries of thinking and practice.
‘How many of us know how to measure the quality, condition and biological function of soils surrounding trees – upon which the roots and health of the tree depend? And how many even have the tools to undertake this before intervening with valued trees under stress or in decline?
‘As professionals we need to develop conventions for soil sampling, analysis and monitoring of the hidden soil-root world that supports tree function and growth. We need to agree indicator metrics to establish a baseline and observe change over tree-time.
‘If we can build a common purpose around this, particularly in the face of environmental and biosecurity threats, it will increase confidence in communicating our role and the positive and negative influences on tree resilience. The Arboricultural Association’s conference partnership with the Sustainable Soils Alliance is testimony to this need and progression.’
Appropriately set within the beautiful grounds of the University of Greenwich, in the Howe Lecture Theatre by the River Thames, the day began with tutors delivering presentations to delegates representing local authority, estate management, consultancy and tree contracting businesses.
Ian Rodgers, Arboricultural Manager for the Royal Parks, provided a background and history of the Parks, including an overview of variations in use and management over the years – demands require balancing of land use, public experience and visitor pressures – and the challenges faced including the impact of increasing numbers of visitors compacting soil around trees, dog fouling altering soil chemistry and the threat of diseases such as ink disease of the sweet chestnut (SID).
Neville Fay (also co-Founder/Director of the Sustainable Soils Alliance and founder member of the Ancient Tree Forum) has long considered the implications of soil health in relation to trees in decline. He believes this should be a concern for owners of large and ageing tree populations in parks and estates and managers responsible for trees at sites of special scientific interest, as well as for those looking after trees located within culturally important and heritage landscapes.
Neville’s presentation explored the theory and results of studies that Treework has been running over a number of years, aiming to address these issues – currently comprising 12 projects and looking set to grow further. The current programme at Greenwich Park and other sites is the result of over 15 years of work, five dedicated to developing theory and study design, and over 10 years in the practical application of treatments and collection of data. This contributes to an evidence-based approach which is now being applied in Greenwich Park, focusing on identifying and addressing Phytophthora that is impacting the sweet chestnut population. The approach monitors the response of trees to different, principally organic, amendments. Species now covered by these projects include oak, plane and lime as well as sweet chestnut.
Lucio Montecchio, Professor of Forest Pathology & Ornamental Trees Pathology at De Rebus Plantarum (a spin-off of the University of Padua) discussed his research focusing on the composition of mycorrhizal communities in relation to forest decline, the ecology of endophytic fungi, the epidemiology and dynamics of forest diseases, and biological control. Professor Montecchio provided a scientific overview of the Phytophthoras implicated in SID, with a strong emphasis on the significant role water plays in relation to infection and the manner in which the pathogen enters and moves through the vessels and tissues within a tree. His presentation included microscope video footage, captured at high magnification, clearly conveying how these pathogens colonise, infect and cause disease damage.
Finally Dr Elizabeth Stockdale, NIAB’s Head of Farming Systems Research and member of the SSA Science Panel, focused on the creation and evolution of soil, including the importance of organic matter and rate of litter breakdown for different environments and tree species. This highlighted the importance of soil as a living system, as well as soil function and composition, and strategies and techniques for assessing soil health.
SoilBioLab provided a bank of microscopes for hands-on assessment of different soil samples including sandy and woodland soils. This was also an opportunity for delegates to witness the many microorganisms – bacteria, fungi, protozoa and nematodes – present in ‘healthy’ soils.
Endotherapy, soil types, compost tea and more
The afternoon session started in Greenwich Park with presentations of the symptoms of SID and the methods being used to address it: ‘endotherapy’, the application of compost teas, and the use of wood chip and biochar.
The session held by Professor Montecchio and his colleague Elisa created plenty of discussion. Delegates were able to first witness and then carry out for themselves the first endotherapy treatment for the study. The system has been developed by De Rebus Plantarum for delivering key nutrients to the crown of the tree via its vascular system, and relies on natural sap movement within the tree. It is less destructive in the long term than some alternative injection methods that can damage the vascular system and create avenues for infection. Once the endotherapy equipment is inserted into the phloem, the solution is poured into small funnels which are attached to it, and delegates watched as the liquid was gravity-fed into the tree. The system is designed to increase the tree’s vitality and improve its defence capacity against the effects of pathogens.
Dr. Stockdale spent the afternoon in large soil pits dug at two locations across the park to illustrate differences in soil in these areas. Her sessions included practical identification of different soil profiles and field indicators of soil function and health.
She said, ‘As a soil scientist, I am happiest in a hole in the ground and at Greenwich Park I was lucky to be able to spend an afternoon a metre into the river terrace gravels that underlie its southern part. My research and knowledge transfer over the last 20 years has been focused on agricultural systems – in which trees get only an occasional mention.
‘There is increasing interest in the development of agro-forestry systems for UK conditions, with trees better integrated into both grazing and cropping systems; already some innovative farmers have nut trees in hedge lines between wheat. Of course, there is a small but important community of horticulturalists working with perennial crops for fruit and nut production. Many of the soils issues that they face are familiar to the arborist too – disruption of the natural cycle of litter return and decomposition, compaction, hydrological change and manipulation. All these factors have impacts on the function of the below-ground biological community and consequently on overall soil health. To what extent these long-term declines in soil health are matched by impacts on tree health is a question not yet fully answered.’
Neville, Ian and Simon Parfey (TEP) led delegates through the trees included in the SID study. Individuals were able to witness applications of compost tea and see the equipment and method developed by TEP to apply a biologically-active solution to tree canopies at height, in addition to treating the soil surrounding the tree.
Rob Grist (Gristman Tree Surgery), demonstrating, elaborated: ‘Compost tea spraying has become a new focus for us, catalysing our engagement with soil microbiology.’
Simon Parfey also runs a specialist soil laboratory – SoilBioLab – which has partnered with TEP on soil projects to provide analytical tests which measure and identify changes across a range of soil parameters. Simon said, ‘The parameters that we have set on this project are based on our extensive experience over many years. This includes an analysis of soil life including concentrations of microorganisms such as protozoa, bacteria, fungi, nematodes and certain ratios together with an assessment of the relationship between tree root and mycorrhizal fungi.’
Simon took the groups through some of the treatments and discussed the thought process, standard and practical application methods of amendments including compost tea. ‘It’s a real privilege to be working among leading minds and innovative new ways to tackle issues in the sector,’ he said. ‘The level of interest in what is a new area for many arborists exceeded my own expectations. There is a real appetite for this kind of information and, as evidenced by Nev’s achievements through the SSA, never has there been a more critical time to start measuring, monitoring and managing our depleted and sometimes exhausted soils.
‘I am sure that we will continue to build upon the knowledge that we have gained through years of work and, together with our evidence-based approach in other soil-related work, such as tree planting, will help inspire others within the arboriculture industry to start thinking about the soil as well as trees.’
The workshop was considered highly valuable by all and illustrated the importance of creating more opportunities to share knowledge on soil within arboriculture, as well as the need to engage with experts from other sectors and disciplines.
David Humphries, Tree Management Officer, City of London Corp, summed up:
‘We found the day to be very engaging in a fantastic location with top class speakers. It has left us with a better understanding of how soils can become depleted leading to the ideal environment for pathogens, and also how compost tea and other soil, canopy and stem treatments can combat pathogens as well as benefiting soil fauna and improving the growing conditions leading to healthier trees.’
The Sustainable Soils Alliance and Treework are supporting the Arboricultural Association to deliver a soil-focused programme for the 2018 Amenity Conference, Soils & Trees – Standing your Ground (9–12 September). Treework will have case studies available and microscopes on hand for studying soil microorganisms, and the three days are packed with experts on trees and soils.