定義： 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.
定義： A soil consisting of the upper layer of soil on the surface consisting of loose material capable of supporting life composed of a mixture of mineral and organic matter.
定義： 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)
