In order to fully flourish, this community requires a minimum of 4.5 hectares of woodland containing decaying aspen and other broadleaved trees. There is in fact a whole specialist community of insects which depend on the dead wood of aspen in various stages of decay, and one of these species – a fly ( Ectaetia christiei) – was only identified by scientists for the first time in the 1990s. Another rare hoverfly ( Callicera rufa), whose larvae rely on rot holes in old pines, has been recorded in Glen Affric.Īt present Trees for Life are taking a particular interest in the saproxylic insects associated with aspen ( Populus tremula), such as the aspen hoverfly ( Hammerschmidtia ferruginea). This species is found in only a few places, including Abernethy, and is threatened by loss of habitat. Then there are some endangered species which specialise on Scots pine ( Pinus sylvestris), such as the pine hoverfly ( Blera fallax) which breeds in wet pockets of decay in large pine stumps. For example, the black tinder fungus beetle ( Bolitophagus reticulatus) (which occurs in Glen Affric) and another beetle ( Bolitothorus cornutus) live in the fruiting bodies of the tinder fungus ( Fomes fomentarius) which is only found on dead birches. Certain insects depend on the fungi which grow on dead trees. A number of these have now become extremely rare, as a result of loss of habitat. InvertebratesĪmong the invertebrates, specialist flies and beetles are particularly well represented. A remarkable 40% of woodland wildlife is dependent on this aspect of the forest ecosystem. There is a breathtaking range of saproxylic (deadwood-dependent) organisms including fungi, lichens, invertebrates, mosses and birds, many of them having very specific requirements, and some specialising exclusively on one particular microhabitat. Standing dead trees (snags) and fallen debris provide a fantastic array of ‘microhabitats’. Fallen logs can also increase soil stability within a woodland. Not only is it an aspect of the process of nutrient cycling, providing a steady, slow-release source of nitrogen, but it is also thought to play a significant role in carbon storage. The value of dead woodĭead wood (coarse woody debris or CWD) is extremely important to the health of the forest, and this is being increasingly recognised by conservationists. Before examining why, let us look at the crucial role which dead wood plays within the forest ecosystem. Today, the average British woodland has far less. Studies in temperate forests in North America and elsewhere suggest that in a healthy, wild forest dead wood can comprise as much as 30% of the overall woody biomass. Most of our remaining woodland is very different from those prehistoric forests, and a key difference is the amount of standing and fallen dead wood in them. A bear emerges from the forest, and pads deliberately across the cool, dappled glade towards a large, rotting stump, which it effortlessly begins to prise apart in a search for grubs…
The forest floor strewn with fallen limbs and trunks, the scents of fresh vegetation and decay mingling in the air. Picture a rich forest-scape with lush undergrowth and trees of all ages, from tiny seedlings, to huge, gnarled giants, some of which are thousands of years old. Britain’s primeval forest: what an experience it would be to visit the Wildwood as it once was.