Definition: A depression caused by erosion by water or ice. Low-lying land bordered by higher ground; especially elongate, relatively large gently sloping depressions of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet.
Definition: This organism produces this material or substance, either during its life or after death. A produces B if some process that occurs in A has output B.
Definition: Arenosols are sandy soils, including both soils developed in residual sands after in situ weathering of usually quartz-rich sediments or rock, and soils developed in recently deposited sands such as dunes in deserts and beach lands.
Definition: A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
