THERE can be few woodlands in Scotland to have emerged totally unscathed from the series of unusually ferocious storms we have endured over the past year.
The damage is all around – huge and once-proud trees lying toppled in fields and many others with gaping gashes in their sides from broken branches. Such destruction may seem a tragedy for the natural environment, but the reality couldn’t be further from the truth, for this deadwood forms an incredibly important habitat for our wildlife.
One only has to sit on the old and decaying trunk of a fallen tree trunk to fully appreciate the diversity of life that now lies within. Peel apart the soft and crumbling bark and inside are myriad tunnels created by thriving populations of specialised invertebrates. On the surface of the trunk are intricate tiny cup-shaped lichens, fungi and many different types of mosses, along with the bullet-mark indentations caused by a foraging woodpecker.
As well as the sheer diversity of life within the deadwood, it also plays an ecologically important role in carbon capture and in the soil nutrient cycle, slowly releasing nitrogen back into the environment. The deadwood is as vital to the health of a woodland ecosystem as is a living oak, with the multitude of species that depend upon it for life.
Even the simple physical result of a tree or group of trees blowing over provides new diversity in the forest. The clearings created bring dappled sunlight to the woodland floor that encourages wild flowers and other growth, which in turn attracts butterflies and dragonflies and numerous other invertebrates that themselves are preyed-upon by shrews, insect-eating birds and bats. The fallen seeds of trees can now germinate and grow in these sunny open places, completing the continuous circle of natural regeneration and delivering new vitality to the woodland.
The snapped-off bough of a tree creates a fissure in the trunk, which depending on the size will attract hole-nesting birds ranging from blue tits to jackdaws and tawny owls, and which also creates a safe and sheltered haven during the cold winter nights. Many of our bat species are dependent upon such holes for their summer and winter roosts. Standing dead trees create excellent look-out perches for birds of prey, while the tangled roots of an up-ended trunk attract nesting wrens and robins. Different varieties of rare types of insect are dependent upon deadwood for their survival, including beetles, hoverflies and sawflies. The endangered pine hoverfly is one such specialist, which breeds in rotting wet pine stumps. It only occurs at a few sites in Scotland, including the old Caledonian pine forests near Aviemore, where it is benefiting from a reintroduction scheme.
Deadwood is also important in other environments. Trees that topple into rivers create hiding places for fish and other underwater life, helping retain underwater sediments and trapping and facilitating the breakdown of organic matter into food for aquatic invertebrates, as well as diversifying the overall integrity of the river by creating pools and riffles.
In the past, forestry managers often removed deadwood from woodlands for aesthetic reasons and also because they thought there were potential hygiene issues from fungal attack and insects. But there has now been a sea-change in thinking and bodies such as Forestry Commission Scotland are working to increase the amount of deadwood on their land, with research showing that considerable gains in biodiversity can be achieved by increasing volumes in plantations.
FCS tells me that it actively promotes the importance of deadwood to its forestry managers, with the UK Forestry and Biodiversity guidelines suggesting that deadwood should amount to around 20m³ per hectare, although this is a target that may take some time to reach.
And, of course, we can all play our role in maintaining such biodiversity by ensuring that our gardens are not too tidy and by having at least some deadwood around, perhaps tucked away in a dark corner. A small pile of logs is ideal. In my own garden there is an old rotting tree stump that is soft to the touch, with the numerous holes and damp wood dust testament to the tunnelling activities of insects – yet no matter how hard I look, I can never see them. But they are there, and that is all that matters.