Posted by: lensweb | November 15, 2019

Let Dead Logs Lie

The Importance of Dead Wood

Wood has played a crucial role in human society for many thousands of years. Fuel is essential, and our ancestors harvested both fallen wood and living trees to meet their needs. This led to the destruction of much woodland, especially if the area was then used for agriculture. At the very least, it meant the ratio of living to dead wood was increased. Fallen dead wood has often been ‘tidied up’ in managed woodland, but the importance of leaving dead wood is now recognised.

One third of all woodland birds nest in holes or cavities in dead trees, and large, hollowing trees provide ideal roosting sites for species such as woodpeckers and owls. Birds may also rely on the invertebrates in dead wood as a food source. Many bats use tree holes for summer and winter roosts. Birds of prey use standing dead wood as lookouts and food handling points. Logs are used by other vertebrates for cover, feeding, lookouts, resting, sunning and hibernating.

A wide range of mosses and lichens can be found on decaying wood, These attractive features add further diversity to the woodland ecosystem. Fungi obtain nutrients from dead organic matter.

Large woody debris plays a vital role in creating diverse ecological niches in water. Fallen logs, can provide cover for fish, and used for spawning. Debris dams gather leaf litter, providing food for fish and invertebrates. By slowing the velocity of a stream, dead wood also helps to reduce soil erosion and regulate flooding.

In dead wood, there is a pattern of decay and breakdown, which is the result of colonisation by other organisms. When a tree dies, the sapwood is invaded by wood-boring beetles such as longhorns. Fungi begin the work of decaying the less nutritious heartwood, as the threadlike mycelia penetrate the tissue and allow entry to other organisms. Along with fungi, bark beetles enter and these soon attract predators and parasites including spiders, false scorpions, and wasps.

Hoverflies, millipedes and mites are associated with the mid-stage of decay, and in the later stages the wood may even be used by small mammals. In the final stage of decomposition, insects are replaced by soil organisms which feed on the bacteria and microfungi that convert the wood to humus. This is the completion of a cycle, by which the nutrients that have been stored within the tree return to the soil.

Studies suggest that in healthy woodland a large percentage of the biomass is dead wood which plays a crucial role within the ecosystem. It has been shown that there is more life in a dead tree than a living one. Dead wood provides a steady, slow-release of nutrient recycling, and plays a significant role in carbon storage.

Dead wood provides living space for a range of organisms including fungi, lichens, invertebrates, mosses and birds, many of them having very specific requirements. These sustain a large percentage of woodland wildlife.

The dead wood and old trees in woodland promote a healthy eco-system which teems with wildlife which thrives on decay and old growth. Good woodland management means leaving felled trees in situ to return valuable nutrients to the soil and provide habitat for dead wood-dependent wildlife. True re-cycling.

Marion Bryce

15 November 2019


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