定義： directly or indirectly modulating the availability of resources to other species, by causing physical state changes in biotic or abiotic materials; modifying, maintaining and/or creating habitats
定義： position of an organism in a food web. May be described verbally with descriptors including primary producer, herbivore or carnivore. If described numerically, 1 indicates a primary producer, 2 a herbivore, and so on up the food web.
