City Trees

May/June 2019

Issue link:

Contents of this Issue


Page 35 of 39

Figure 7. A "monolith" of beech (Fagus sylvatica) over an eleven-year period, showing that initial obvious decay by macro-fungi slows down as the wood becomes "spent" and a slower decay process then follows. Taking the crown off a tree that is defective at its base, but leaving the standing stump is now quite common practice in parks and gardens in the UK—a process that has come to be called "monolithing" here, although that literally means the creation of a standing stone, not the creation of a standing stump. In the US, I've heard that they are called "wildlfe snags," which makes more sense. I have a lot of TOT images of these man-made snags, as I am intrigued about their degradation over time, what wildlife makes use of them as micro-habitat, and their longevity. In the UK, there is little guidance on the creation of these snags, some of which are created out of trees with non-durable wood and set at heights that do not fully remove the risks from structural failure. My initial analysis of my revisits identify that a snag is more durable if left at a lower height, and also that some species (such as Castanea and Quercus) make better longer-term snags than others (such as Acer and Fagus), due to having a more durable timber. I hope to carry out research that informs the arboricultural industry about wildlife snag selection, choice of height, and assessing the risks of failure in subsequent years. Figure 6. The decline of an old hedgerow oak tree (Quercus x rosacea) after the building of a business centre, the topping of the tree (for no obvious reason), and the development of a parking lot close to its trunk, over a ten-year period. Education is a key aim of the TOT project—and a number of people that worked on this development project clearly need to be better educated about trees and how to care for them. Treated well, an oak of this species can persist in the Lancashire landscape for six hundred years. But topped, root severed, and the ground around it compacted, the lifespan of this tree has been greatly foreshortened. Often, I have audiences of arborists who have all seen this effect, who are well- educated and know how to care for amenity trees. It would be far better to escape this "echo chamber" and be able to talk to the people who are ignorant about trees and who enact works like this, which endanger valuable old trees. Unfortunately, invitations to give such talks do not arise: people don't want to know, it seems, that they are irreparably damaging the landscape around them. These sorts of TOT images I think are of great value to my students, for they may see developments enacted near to trees and little change in such trees for the first couple of years: the tree's deterioration is often longer-term. Very often (and rather dismally), trees come off badly when people enact a development on their land. 36 CityTREES

Articles in this issue

Archives of this issue

view archives of City Trees - May/June 2019