Community Composition and Biomass Distribution

[9709559] Naeem在大多数调查尺度上，生物群落的组成差别很大。群落组成的变化在小型生态系统中尤其普遍，在那里，局部灭绝、殖民化和生物入侵是司空见惯的，但大型群落也可以说正在经历这些变化。群落属性对这种组成变化有多敏感？模式是否可以预测？尽管群落对群落组成的微小变化也表现出巨大的反应范围，但各种各样的理论表明，这种广泛的反应范围是可以预测的。这一理论体系的基础是物种在营养行会中的代偿能力、相互作用强度的分布以及群落中营养类群的数量。然而，检验这一理论所必需的大量复制社区却限制了经验探索。这项研究将使用在受控环境条件下饲养的淡水微生物群落的小型类似物，并进行充分的复制，以测试这一理论。实验采用组合和固定结构两种方法来改变群落的组成，以产生包含2、3、5或5个营养水平的群落，每个水平有1至5个物种。自养和异养生物量将作为群落响应变量进行测量。设计了三组实验来明确评估补偿生长和相互作用强度在确定生物量分布模式中的作用。这项研究将对一组特定理论与其生物类似物之间的界面进行深入探索。它将把实验结果与基于等效性和独特性的理论联系起来，以预测生物量分布与群落组成的关联模式。

9709559 Naeem The composition of biological communities varies enormously over most scales of investigation. Changes in community composition are especially prevalent in small ecosystems where local extinction, colonization, and biological invasion are commonplace, but large communities are arguably experiencing such changes as well. How sensitive are community properties to such variation in composition and can patterns be predictable? Although communities exhibit a tremendous range of responses to even small-scale changes in community composition, a diverse body of theory suggests that this broad range of responses is predictable. This body of theory is based on the compensatory abilities of species within trophic guilds and the distribution of interaction strengths and the number of trophic groups in a community. The large number of replicate communities necessary for testing this theory, however, has limited empirical explorations. This research will use small analogs of freshwater microbial communities reared under controlled environmental conditions with sufficient replication to test this body of theory. Composition is experimentally varied using both assembly and fixed-structure methods to produce communities that contain 2, 3, 5, or 5 trophic levels with 1 to 5 species per level. Autotrophic and heterotrophic biomass will be measured as community response variables. Three sets of experiments are designed to explicitly assess the roles of compensatory growth and interaction strengths in determining patterns in biomass distribution. This study will provide an in-depth exploration of the interface between a specific set of theories and its biological analogs. It will link experimental results with equivalency- and uniqueness-based theory to predict patterns in the association of biomass distribution with community composition.