(View exact match)earthwormSYNONYMS OR RELATED TERMS: angleworm
DEFINITION: Any of nearly 2000 species of terrestrial worms which act as one of the main agents by which plant litter, humus, and minerals are incorporated and mixed in soil. Earthworms are responsible for the maintenance and stability of various types of soil, especially the brown forest soils. The character of a soil may change markedly if the plant litter made by the vegetation changes to a kind which is unpalatable to earthworms. The effects of earthworm sorting may be seen on archaeological sites in the blurring of layers and the development of worm-sorted layers in the top of buried soils. Earthworms usually remain near the soil surface, but they are known to tunnel as deep as 6 feet during periods of dryness or in winter. Indirectly they provide food for man by aerating the soil, promoting drainage, and drawing organic material into their burrows where it decomposes faster, thus producing more nutritive materials for growing plants.
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brown earthSYNONYMS OR RELATED TERMS: brown forest soil, brown earths
DEFINITION: Brown forest soils that result from prolonged forestal conditions and which develops under mature deciduous woodland. Brown earths are thought to have covered most of the British Isles and temperate Europe under the great forests which existed during the middle of the present Interglacial. The soil type is penetrated by tree roots and actively worked by earthworms to a considerable depth. The top is well-mixed mineral material and humus. As a result of woodland cover being removed repeatedly, these soils are rare today.humusCATEGORY: geology
DEFINITION: Decomposed organic matter which becomes incorporated into soil. Litter from plants (organic matter) on or near the surface of the earth is slowly broken down by soil organisms (decomposed and oxidized) into fine particles, which may then by incorporated into the soil by earthworms and other soil organisms. It may be combined with the products of the decomposition of various rocks and then forms the soil in which plants grow.