CWD is important actor contributing to soil nutrients cycles. CWD, while itself not particularly rich in nitrogen, contributes nitrogen to the ecosystem by acting as a host for nonsymbiotic free-living nitrogen-fixing bacteria. Scientific studies show that coarse woody debris can be a significant contributor to biological carbon sequestration. Trees store atmospheric carbon in their wood using photosynthesis. Once the trees die, fungi and other saprotrophs transfer some of that carbon from CWD into the soil. This sequestration can continue in old-growth forests for hundreds of years. Habitat By providing both food and microhabitats for many species, coarse woody debris helps to maintain the biodiversity of forest ecosystems. Up to forty percent of all forest fauna is dependent on CWD. Studies in western North America showed that only five per cent of living trees consisted of living cells by volume, whereas in dead wood it was as high as forty percent by volume, mainly fungi and bacteria. Colonizing organisms that live on the remains of cambium and sapwood of dead trees aid decomposition and attract predators that prey on them and so continue the chain of metabolizing the biomass. The list of organisms dependent on CWD for habitat or as a food source includes bacteria, fungi, lichens, mosses and other plants, and in the animal kingdom, invertebrates such as termites, ants, beetles, and snails, amphibians such as salamanders, reptiles such as the slow-worm, as well as birds and small mammals. One third of all woodland birds live in the cavities of dead tree trunks. Woodpeckers, tits, chickadees, and owls all live in dead trees, and grouse shelter behind woody debris. Some plants use coarse woody debris as habitat. Mosses and lichens may cover logs, while ferns and trees may regenerate on the top of logs. Large fragments of CWD that provide such habitat for herbs, shrubs, and trees are called nurse logs. CWD can also protect young plants from herbivory damage by acting as barriers to browsing animals. The persistence of coarse woody debris can shelter organisms during a large disturbance to the ecosystem such as wildfire or logging. Rivers and wetlands Fallen debris and trees in streams provide shelter for fish, amphibians and mammals by modifying the flow of water and sediment. Turtles of many species may also use coarse woody debris for basking. Musk turtles may lay their eggs under logs near wetlands. Soil Coarse woody debris, particularly on