After the recent heavy rains along the Churnet Valley I notice windblown trees are sliding towards the Coombes Brook about to become brook trees -‘large woody debris’. The process is aided by the steep sides to the Coombes Book in many locations through Coombes Valley.
Large woody debris can help protect the brook from erosion trapping silt, resisting and deflecting flows of water. Trapping silt oxygenates the water improving water quality for aquatic life. Logs in a stream create pools that can be used by spawning fish, helping to create complex microhabitats for a wide range of plants and animals.
Brook trees - Large woody debris at Coombes Valley
Large wood debris branches also trap smaller coarse woody debris. Woody debris provides a huge range of habitats such as hollows, splits and cavities for algae, microscopic life and invertebrates. In stream wood increases the amount of wildlife at the base of the chain that will benefit birds like the Dipper and Grey Wagtail at Coombes Valley. Woody debris provides a perch for birds and an escape route for adult mayflies, caddis flies and dragonflies to emerge from the water to complete their life cycle. In a research report on woody debris Natural England say that there are 147 invertebrates species strongly associated with woody debris in streams. For example the crane flies or 'daddy long legs' - Lipsothrix nobilis / nigristigma are UK Biodiversity Action Plan (BAP) species where the larvae live in coarse woody debris.
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