图3. 结构稳定性理论的基础数学框架。和经典的群落结构-物种共存理论相比, 结构稳定性理论引入了环境因子。环境因子同时会影响群落结构和物种共存。结构稳定性(SS)的计算需要两部分的信息: 共存域(CD)和环境域(ED)。共存域指的是可以使得物种共存的全部参数的空间, 图中用蓝色区域(图A)指代。共存域是由群落结构通过群落动力学而决定的。环境域指的是这一环境条件下所有可能的参数的空间, 图中用绿色区域(图B)指代。环境域是在给定环境的限制下所有可能的参数的空间。环境域是环境因子决定的。结构稳定性是共存域相对于环境域的大小。结构稳定性越大, 物种在这一环境条件下就有更大可能可以共存。

Fig. 3. The mathematical framework of the structural stability approach. To compute the structural stability (SS) of an ecological community, we need two pieces of information: the coexistence domain (CD) and the environment domain (ED). The coexistence domain (denoted in blue; region A) is the full range of parameters that are compatible with species coexistence. The coexistence domain is determined by the community structure via the ecological dynamics. The environment domain (denoted in green; region B) is the full range of parameters constrained by the given environmentally conditions. The environment domain is determined by the environmental factors. Structural stability is defined as the relative size of the coexistence domain comparing to the environment domain. The larger the structural stability is, the more likely species can coexist under the given environmental conditions.