Spring is just around the corner and it is our last chance to appreciate the bare trees and the amount of dead wood left in East Dartmoor National Nature Reserve. Here we understand the value of these carbon stores and the wildlife value they hold: a dead tree creates a gap in the canopy for the next generation of trees to grow; the leaf litter created in autumn by fallen leaves is a valuable food source and habitat, and if left to decay will release essential nutrients into the soil. It’s not an ending, just another phase in a continuous cycle. Despite this month’s cold weather, you’ll be able to see catkins and snowdrops starting to appear in your local greenspaces and parks.
Snowdrops on a woodland bank in the NNR (photo: Simon Smith); The pendulous, yellow, male catkins of hazel are also know as ‘lamb’s tails’ (photo: WTML)
The leafy woodland food bank
All life needs food, and in a woodland it’s the dead leaves, branches and plants that provide the raw materials. Decay and decomposition are often seen as the negative stage of a plant’s lifecycle, yet the goodness in this year’s leaves will help fuel the growth of future generations. The woodland food bank includes an army of unsung workers. It starts with a wide range of invertebrates including earthworms, beetle larvae, and millipedes, as well as slugs and snails. As the leaves are broken down and pulled into the soil by the earthworms, the surface area that fungi and bacteria can live on increases. One of our main recyclers the wood ant will be emerging soon and can be seen on warmer days as we move into spring.
Bracket fungi feed on living and dead wood (photo: Jane Halliday); Winter colours on the woodland floor
While we often only notice the fruiting spores of fungi, under the surface they have an intricate web of feeding threads or hyphae that look like fine plant roots. The hyphae break down the dead plant material by releasing acids and enzymes. The nutrients which are released including nitrogen and phosphorus, provide the food that the fungi need as well as, enriching the soil and making them available for trees and other plants. Sustainability to the core.
Dead wood homes
You may have noticed more fallen branches and dead wood being left at East Dartmoor NNR and your local greenspaces. It’s a recognition of the importance of allowing trees to grow, live and die naturally. During their lifetime, a tree will contain both living and dead wood, caused by a mixture of wind or animal damage, lightning strikes, or lack of light. This dead and damaged wood provides a wide range of roosting and nesting opportunities for woodland birds and bats, as well as micro habitats for invertebrates and fungi.
It’s estimated that more than 2,000 species of invertebrates live on decaying and dead wood in Britain alone. As the mix of deadwood changes, so does the range of invertebrates and many are in decline due to the removal of dead and decaying wood. It also impacts on woodland birds. Across Europe nearly a third of woodland birds use tree cavities for roosting and nesting sites, and research has shown that the type and number of tree cavities is a limiting factor on their numbers.
About 75% of native bat species roost in trees and because they can’t bore holes, they make nests in natural cavities or ones that have been made by other animals including woodpecker holes. During the winter months they use holes that are either deeper or lower in the tree where its warmer, and during the summer move upwards towards the canopy for the same reason.
Long lived native trees like the oak, beech, ash, hornbeam, and elm are the most valuable sources of deadwood and cavities because of their long life, slow decay rate and large size. At the other end of the scale is birch, whose shorter life and quicker decay rate can develop cavities and deadwood in 70 years, compared to a 100 years for oak, beech and ash.
The value of the natural approach
In the NNR we leave trees to die in situ wherever we can (where safe to do so), even if fallen. Research by Albrecht (1991) demonstrated the staggering difference of 50-200m3 of deadwood in unmanaged woodlands compared to 1-5m3 in ones that followed a clear felling cycle. Closer to home, and if you have your own green space, you can make a difference by leaving leaves, dead and damaged branches, and log piles that invertebrates and small mammals can eat and shelter in.
Written by Jane Halliday for the Fingle Woods Blog (with some additional notes on East Dartmoor by Albert Knott)
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