Hidden Life in the deadwood
By Katie Halsall
What is deadwood? Deadwood consists of a range of micro-habitats, and includes fallen dead tree material, such as branches or trunks, standing dead trees, and cavities such as rot holes in living trees. The quality of a deadwood microhabitat changes over time, as wood will decay at different speeds depending on it’s size, species, and location. This means that the types of species you will find inhabiting each micro-habitat will differ depending on which stage of decay the wood is in.
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There is a huge variety of specialist species living in deadwood, known as saproxylic organisms, and these are dependent on deadwood, but may also be micro-habitat specific too. Organisms include invertebrates, fungi, lichens and mosses. Around 40% of woodland wildlife is dependent on this section of the woodland ecosystem, and this includes the saproxylic organisms, nesting birds and mammals.
What does deadwood do? Decomposition and decay are vital processes in nature. They play an essential role in the breakdown of organic matter, making it available for other organisms through recycling. Without these two processes, nutrients from dead plants and animals wouldn’t get back into the soil and would instead remain in the dead material. Thus, there would then be a shortage of nutrients for the animals that rely on these processes. Futhermore, the decomposition of wood has many different uses and effects.
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+ Deadwood provides a habitat for the organisms that live, feed or nest in decaying wood. + It maintains forest efficiency, by providing organic matter, nutrients and regeneration sites for trees. Decaying wood helps to stabilising the forest, as soil is produced, helping the stability of the ground and preventing soil erosion. + It supplies a food source for specialised feeders, such as beetles and fungi, as well as the woodland birds or mammals which feed on these saproxylic organisms. + Long-term effects include the storage of carbon, which in effect helps with some of the impacts of climate change.
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different Stages of deadwood
decay
+ Living veteran trees will contain cavities which large nesting birds such as owls will utilise. Deadwood on live trees may be used by invertebrates such as hoverflies and beetles. + Standing dead trees include trunks of different ages, and these may be colonised by invertebrates, fungi, lichen and ferns. Young dead trees may be used by specialised fungi and bacteria. + Lying timber includes fallen logs in a variety of different stages. To begin with, fungi and bark and wood-boring beetles will appear for the sapwood. These attract predators such as spiders, and the parasitic ichneumon wasp. + When the wood has begun to soften inside, more beetles and fungi will be present. Fungi will begin the decay the less nutritious heartwood, allowing other organisms to enter the deadwood. + As the outer layer of wood softens, fewer fungi will be present, but more insects will appear. A well decayed log will be used by specialised fungi and a variety of insects. + An almost completely decayed log, with powdery wood, will be used by insects such as woodlice and millipedes. + Litter in the soil comprises of large woody debris, which works as a substrate for flowering plants, and smaller fragments of the woody debris used by woodlice and specialised fungi.
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A natural forest would hold most types of deadwood, however management systems mean that deadwood has consistently been removed from woodlands for firewood. Deadwood was also removed from managed forests due to the thought that doing so would clean the woodland and keep it looking tidy. This led to a widespread poorness of biodiversity in woodlands. 7
small life Saproxylic invertebrates are dependent on dead or decaying wood, on wood fungi or other saproxylic invertabrates, however they may not be dependent on the wood at every stage of their life cycle. For example, the Stag beetle larvae feed on wood, but the adults feed on tree sap. This group of organisms is hugely diverse, and includes lichens, fungi, invertebrates, bryophytes and holenesting birds or mammals. Despite the variety, beetles are the most represented species and estimates state
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that between 22-56% of forest beetles are saproxylic. Deadwood and decaying wood hold a huge variety of microhabitats, and different saproxylic insects will inhabitat these according to the tree species, decaying stage and the position of the tree. Some hoverflies prefer rot holes and crevices in standing trees, whereas some beetles may prefer large snags and logs. Deadwood is an important habitat for birds too: the crested tit will nest in a well-decayed snag or
stump, and a Wryneck will nest in old woodpecker holes. Invertebrates such as centipedes, beetles and woodlice will use the detritus that accumilates in crevices and rot holes, which effectively will then provide food for birds such as the tree creeper and redstart. Furthermore, holes in dead trees are what bats mostly depend on for their roost sites. As you can see, dead and decaying wood can support a variety of species, each using a different stage of the process.
Effectively, these insects help to create new habitats within the deadwood, provide habitats for parasitic species and have been found to play a part in pollination. Saproxylic invertebrates, as well as fungi and bacteria, are a crucial part of the decomposition process; they consume the dead wood and release the nutrients by changing them into other forms of organic matter. This goes back into the cycle to be consumed by other organisms. Thus, these species play a huge role in nutrient-cycling in the forest ecosystem.
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Finding Fungi Wood-decaying fungi depend on both fallen and standing deadwood, and in turn this fungi supports a huge diversity of invertebrates including predatory beetles and fungus gnats. Various tree species support wood-decaying fungi, however oak trees support around 20 different species that specialise of branches, trunks and stumps.
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Fungi are mostly the first instruments of decay, and many species grow in the deadwood. This growth helps other species to gain access to the inside of the wood: the fungi feed on the cellulose and lignin in the wood, converting this into their softer tissues, which in turn decompose when the fungi fruiting body dies.
Types of fungi
+ Gill fungi are fleshy and often have a distinct stem and cap. The spores are produced underneath the cap on gills, tubes or spines. + Bolletes mostly share the same characteristics: a soft, fleshy body and spores produced in a tubular layer. These species are almost all edible too, with just a few being too bitter or upsetting. + Bracket fungi and tbeir relatives (toothed fungi, chanterelles) are a very diverse group and vary in size and shape. They can be tough and fleshy, or hard and woody, and many species are edible. Brackets can be pests and cause serious losses of timber. + Puffballs and stinkhorns are actually a group of unrelated genera that have adopted similar sporedispersal mechanisms. + Cup fungi are mostly microscopic, with many being important pests.
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