定義： a plant that grows low to the ground, has numerous small leaves and a closed, tightly-packed canopy with dense non-photosynthetic living and dead plant tissues below the canopy
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 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)
