定义：Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
定义：Determined for type of life cycle being annual, biennial, perennial etc.
评论：The life cycle habit indicates the typical duration of an individual plant's life. Common values are annual, biennial, and perennial. Some plants have different durations depending on environment or location, so a plant can have more than one value.
定义：Of plant duration, a plant whose life span extends over more than two growing seasons, c.f. annual, biennial, ephemeral, of flowering with respect to architecture, hapaxanthic, monocarpic, pleonanthic
定义：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.
定义：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)
