A nurse log is a fallen

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

which, as it decays, provides ecological facilitation to seedlings. Broader definitions include providing shade or support to other plants. Some of the advantages a nurse log offers to a seedling are:

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta ('' sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and ...

thickness,

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...

mycorrhizae A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plan ...

, disease protection, nutrients, and sunlight. Recent research into soil pathogens suggests that in some forest communities, pathogens hostile to a particular tree species appear to gather in the vicinity of that species, and to a degree inhibit seedling growth. Nurse logs may therefore provide some measure of protection from these pathogens, thus promoting greater seedling survivorship.

Occurrence

Various mechanical and biological processes contribute to the breakdown of

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...

in fallen trees, resulting in the formation of niches of increasing size, which tend to fill with forest litter such as soil from spring floods, needles,

, mushrooms and other flora. Mosses also can cover the outside of a log, hastening its decay and supporting other species as rooting media and by retaining water. Small animals such as various squirrels often perch or roost on nurse logs, adding to the litter by food debris and scat. The decay of this detritus contributes to the formation of a rich

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

that provides a seedbed and adequate conditions for germination. Nurse logs often provide a seedbed to conifers in a

temperate rain forest Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain. Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of North American Pa ...

ecosystem.

References

Books

* Montagnini, Florencia, and Benedict, Carl F. Jordan (2005). ''Tropical Forest Ecology: The Basis for Conservation and Management'' (1st ed.). Berlin: Springer. . * Noss, Reed F. (Ed). ''The Redwood Forest: History, Ecology, and Conservation of the Coast Redwoods'' (1999). San Francisco: Island Press. * Mathews, Daniel (1999). ''Cascade-Olympic Natural History'' (2nd ed.). Portland, Oregon : Raven Editions. {{ISBN, 0-9620782-1-2

External links

* Mangan, Scott A., et al
"Negative plant–soil feedback predicts tree-species relative abundance in a tropical forest"
''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans ar ...

'', New York, 2010-June-25. Retrieved on 2010-June-25 Dead wood Ecology