In Defence of Dead Wood

It was once believed that when a tree died, it was no longer of use. For decades, we have actively removed trees at the first signs of rot or fungal attack, felling them at the base and removing all evidence of their existence…

Our guest editor, Nick Gates, Naturalist, writes

Storm damaged trees are hastily sectioned for firewood or bio-fuel. Sometimes, we replace them with a new, younger version of themselves. It was thought that this in turn kept other trees healthy, and that the wider environment benefited as a result.

The fall of a tree opens up new opportunities…

But nothing is further from the truth. By removing this deadwood, we are stripping out a most vital layer of the natural world. Because when a tree dies, it isn’t actually dead.

As a tree grows, its core begins to die. Have you ever looked at a majestic old oak, its core completely hollowed out, and wondered how on earth it was still producing green leaves and fresh shoots? The reason is that only the outer layers of the wood, just below the bark, are alive. They transport all the water and nutrients that a tree needs to survive. Simultaneously, under the soil, a massive network of fungi around its roots help the tree collect all of the vital nutrients and minerals it needs. As the tree grows, the wood core, the growth rings left behind and superseded from previous season, slowly dies.

Left to fade away…

Over time, this core wood is slowly broken down by fungi. In the very oldest trees, the core is lost completely. Perhaps the most famous of these wood-feeding specialists is one you may well have eaten, the Shiitake mushroom. The fungi in turn are eaten by many species, from bacteria to nematodes, insects to mammals, whilst the rotten wood supports many more. Therefore, this soft rotting deadwood actually hosts a complex living food web.

St Andrews Park – The fallen Black Poplar

An oak tree supports over 350 different varieties of insect. But over half of these feed on dead parts of the oak tree.  Bats rely on deadwood cavities to roost, whilst feeding on many species of night-flying beetle that feed solely on deadwood. Redstarts require hidden cavities to nest, whilst searching for bark beetles and moths that grew up in the deadwood. Everything from blue tits to woodpeckers and wood mice to tawny owls rely on deadwood for some part of their existence. By the time an old tree falls completely, upended from its rotting root network, the wood may be dead but the vast diversity of creatures it is feeding are very much alive. 

When we strip out deadwood from a natural environment, often under an aesthetic tidiness premise, we aren’t just taking the wood away. We are slowly eroding the complex living food web that the deadwood feeds. The Bristol Downs has suffered from this for many years. We could have hedgehogs snaffling snails from deadwood retreats and spotted flycatchers nesting amongst the craggy cavities in gnarled out stumps. Animals just need food and shelter to thrive. By removing deadwood, we take away both. There are many ways of leaving deadwood that look aesthetic whilst appreciating the enormous ecosystem service it provides. Good signage can help explain this.

In a time of unprecedented ecological collapse, we must all do what we can to help the natural world. Leaving deadwood in situ is one of the easiest ways to do this. So please, next time you see a fallen tree, don’t look on it as an untidy addition to the landscape, but enjoy it as the next opportunity for nature to reclaim a part in our everyday lives.

@NTGates Feb. 2020

Ancient and Veteran Trees explained

These two terms are in common use, but they have specific meanings when it comes to their conservation. All ancient trees are veterans, but a tree may qualify as a veteran without being ancient.  Most British trees increase in girth over their lifetimes by 2.5 cm a year. They grow faster when young, when in the open as opposed to woodland, and when in good soil rather than bad. They grow slower as they get older. Some species grow faster than average, such as Black Poplar, Plane, and Wellingtonia, and some more slowly, especially Limes and Hawthorns.

Trees are very good at vegetative reproduction, so that they are effectively eternal. Some create their own clumps, each tree being a clone. They do this by branches that arch down to the ground, root, and send up new vertical trees. The Tortworth Chestnut, which was regarded as ancient in King Johns reign, is a good example, but some of the limes on the Downs are doing this. Some trees send up new shoots from the base of the trunk which eventually replace the original tree. Many trees if cut to the ground, by storm or men, will promptly create new shoots, and this is the basis of coppicing which was a standard woodland management tool from at least Roman times. There is a Small-leaved Lime at Westonbirt Arboretum that now consists of a ring of clones about forty metres in diameter.

Ancient trees should be at least two hundred years old, and hence have a girth of more than five metres. I have measured 120 trees in Bristol with this girth, and there are many more in Ashton Court that I have not checked.   They matter because they provide a range of habitats to a range of species. They are always hollow, often squat,  having long since lost their upper branches, their hearts eaten out by fungi and beetles, full of nooks and crannies, and often clothed in lichens and ferns. They are most frequently Oaks, Sweet Chestnuts, Planes and Cedars.

Veteran trees are defined by their individuality. They will be mature, around 140/150 years old, about three metres in girth, mostly still standing tall. Fine, significant specimens of their species both in form and biodiversity. They are candidates to become Ancient, they may be starting to go hollow, and hence be of concern. They may need management to avoid their becoming top heavy, or developing a dangerous lean. They will stand out from other trees in their particular locality and may have planning protection as a consequence. They may also have special features of note, such as being multi-trunked.

Trees and Planning

The National Policy Planning Framework document (issued in July 2018) has the following definitions at Appendix 2: Glossary.

Ancient or veteran tree: A tree which, because of its age, size and condition, is of exceptional biodiversity, cultural or heritage value. All ancient trees are veteran trees. Not all veteran trees are old enough to be ancient, but are old relative to other trees of the same species. Very few trees of any species reach the ancient life-stage.

Ancient Woodland. An area of woodland that has been wooded continuously since at least 1600 AD. It includes ancient semi-natural woodland and plantations on ancient woodland sites.

Irreplaceable habitat: Habitats which would be technically very difficult (or take a very significant time) to restore, recreate or replace once destroyed, taking into account their
age, uniqueness, species diversity or rarity. They include…ancient woodland and ancient and veteran trees….

Paragraph 175 (at page 51) of the framework states:

When determining planning applications, local planning authorities should apply the following principles:

c) development resulting in the loss or deterioration of irreplaceable habitats (such as ancient woodland and ancient or veteran trees) should be refused, unless there are wholly exceptional reasons and a suitable compensation strategy exists;

Paragraph 2.17.6 of DM17: Development Involving Existing Green Infrastructure – part of the Bristol Local Plan echoes this:

Due to their characteristics and value, Aged and Veteran trees are considered to be of relatively greater importance than other trees and even trees of a similar species. Aged trees, by definition, have developed characteristics associated with great age and often have particular landscape and townscape value. Veteran trees are considered to have particularly important nature conservation value. Both will often have significant visual amenity, and potentially historic and cultural importance. As such their loss or harm will not be permitted, and the design and layout of development will be expected to integrate them into development.

These guidelines apply whether the tree or woodland grows in a public or a private place.

R L Bland

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