Lantra Article – Tree Dynamics
Trees are more dynamic than we often appreciate.
Britain is home to tens of millions of trees, each actively contributing to the immediate environment around them, and much of this unseen, even unknown. The local park, a place of relaxation, is often formed around prominent trees under which residents gather and socialise. The trees provide so much more than being a focal point, cleaning air, reducing temperature fluctuations.
There is a view that trees are easily replaced, and within the context of developments, multiple replacements are often proposed to mitigate the loss of the original. It is true that, in the right situations, nature does recover from damage. Regeneration projects that have restored former industrial sites, where there is now little evidence of the previous operations. Where there is time and space, trees can do much to restore.
Trees do not function in isolation. They are often the glue, the infrastructure, to the landscape, the environment. They are the largest individual organisms, linking the soil and the atmosphere. They are often hosts to their fellow organisms, which depend on them. We used to paint fungicide on wounds to prevent fungi from infesting a tree following pruning. Then we had a revelation: there are many fungi already present in our trees. In one trial, Professor Lynne Boddy took a sample of Beech wood from Burnham Beeches and placed it in laboratory conditions. 17 different species of fungus soon emerged, having been waiting in situ for preferred conditions.
We have known for some time that different species of trees have different responses to pathogens. For example, the fungus Daldinea concentrica is unable to become established on London Plane unless the individual tree is under stress. However, Ash trees are often vulnerable to it and unable to defend themselves. We now know that each fungus has a fatty acid associated with it, which enables the tree to detect its presence and respond accordingly. Except that Ash seems unable to detect the fatty acid of Daldinea. We can lend a helping hand with an injection of the defence, but it is rarely cost-effective for members of this species!
We can protect trees based on their visual contribution to a location. However, contribution to ecology is equally valuable and easily overlooked. When the environment around trees remains unchanged over centuries, the ground conditions become rather valuable. They can become host to rare and important fauna and flora, some of which are unable to move to other locations. When leaf litter is allowed to accumulate over the decades, it begins to form an important, invaluable and irreplaceable organic feature in which fungi and micro-organisms can flourish. These organisms are sensitive to changes in the ecosystem and rarely respond to being moved, for example by translocation for habitat management in connection with developments. This is part of what makes Ancient Woodland so valuable and precious. It contains at least 500 years of undisturbed ecology which needs to remain in situ to retain its key features.
We can often seek to focus on managing trees as healthy organisms, resources being allocated to this through mulching, careful pruning and aerating the soil, for example. However, rather like a father figure in the corporate world taking on a new role of wise counsellor with age, with a strategic over view of observation, the aging tree begins to development new attributes. Cavities become home to birds, mammals and flora. There is shelter and shade for the new generation of saplings as they grow, and now dead branches become a valuable niche habitat for saprophytic organisms, which are often utterly depending on the unique environment afforded them by the decline. There are fungi which can grow on standing dead wood, but soon disappear when the material falls to the ground.
Whilst we cannot recreate the unique conditions of a 500-year-old ancient woodland, we can create some of the features found on ancient trees within it, by mimicking the natural pruning which has often occurred. Sometimes, our intervention has unexpected actions and benefits. A woodland which had been requisitioned by the Ministry of Defence during WWll had become home to rare lichens. It was used for exercises over the years, the bullets from soldiers in training causing damage to the bark of many trees. It was then deemed surplus
to use and was soon peaceful. It then became evident that the absence of bullets was harming the delicate ecology, lichens no longer having access to bark wounds. The army was soon invited back in for some shooting practice!
We have known that trees respond to light and to gravity. We now know that some trees can sense small changes in temperature, adjusting photosysnthesis accordingly. They can respond to toxins in the soil, changes in wind direction, temporary drought and excess. Research is on-going to identify the parts of trees that know how to respond, so that we can select species for the conditions they may encounter in the landscape.
Trees are truly dynamic. We still don’t know how they can detect changes in the external environment and respond as they do. Indeed, the more we find out about them, the more we realise how little we actually do know. Which makes the premature loss of trees less easy to understand, and highlights how they need us as advocates, sharing the message of their contribution more widely.