16th March 2017
Managing standing dead veteran trees
David Humphries, Trees Management Officer for the City of London, writes about veteran trees retained as standing dead wood at Hampstead Heath
Although not an ancient tree the veteran boundary oak (Quercus robur) above has now been retained at an acceptable level of risk, as a standing dead structure for its niche habitat and biodiversity value. It was in vascular decline for a number of years following significant storm damage in the 1990s, and it eventually succumbed naturally due to loss of canopy and to a poor partial rooting environment. The oak sits next to a well-used path in an urban open space with regular footfall within a couple of meters.
Consideration was given to maintaining the whole tree to allow natural decline and disintegration by moving the path, but access and environmental factors were restrictive. We therefore decided to manage the risk to the public by incrementally reducing the tree toward a standing stem over a 10 year period, and carrying out an annual inspection of its stability. Before each section or branch is removed we check the loose bark and cavities for signs of habitation by bats and other wildlife. At Hampstead Heath we maintain a large number of dead standing trees to provide habitat until younger oaks can do so once they have become veterans and ancients themselves.
The oak tree is host to a wide array of successional fungal species from the heart wood decayers of Laetiporus sulphureus (below) and Fistulina hepatica that have been active for many decades through to the benign species like Ganoderma lucidum that act more saprophytically on the dysfunctional wood. This decay activity provides the ideal environment for a myriad of saproxylic invertebrates, mammals and birds, a large number of which are very rare and threatened. Other notable species associated with this monolith are Kestrels, Hornets and Stag beetles.
When we have the time we try and utilise fracture and coronetting to finish the cuts – techniques that were developed to mimic the way that tears and fractured ends naturally occur on trunks and branches. The results leave the trees with a more natural aesthetic.
Standing dead trees are appreciated for their cultural and heritage value as well as their biodiversity, as demonstrated by this recent photograph of an artist painting the oak on Hampstead Heath .