Community Composition and Biomass Distribution

9709559 Naeem生物群落的组成在大多数调查尺度上变化很大。群落组成的变化在小型生态系统中尤其普遍，在这些生态系统中，局部灭绝、殖民化和生物入侵是司空见惯的，但大型群落也可能经历这种变化。群落特性对这种组成变化的敏感程度如何？模式是否可以预测？尽管社区对社区组成的小规模变化表现出各种各样的反应，但各种各样的理论表明，这种广泛的反应是可以预测的。这一理论体系的基础是营养团内物种的补偿能力，以及群落中营养团数量和相互作用强度的分布。然而，测试这一理论所需的大量复制社区限制了实证探索。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，以测试这一理论体系。组合物的实验不同，使用组装和固定结构的方法，以产生社区，包含2，3，5，或5个营养级，每级1至5个物种。自养和异养生物量将作为社区响应变量进行测量。三组实验的目的是明确评估的作用，补偿性生长和相互作用的强度，在确定模式的生物量分布。这项研究将深入探索一套特定的理论及其生物学类似物之间的界面。它将把实验结果与基于等效性和唯一性的理论联系起来，以预测生物量分布与群落组成之间的关系。

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.