Dissertation Research: Mechanisms of Species Compositional Change Due to Gap Creation in a Tallgrass Prairie

9701250 Goldberg在这项提案中，PI开发了一个框架，以确定在创建间隙后物种组成变化的机制。这是至关重要的，我们了解这些变化的机制基础，了解的过程，从而开发模型，差距动态。释放竞争，由于减少邻居的生物量已被假定，但在很大程度上未经检验，机制负责物种组成的变化，干扰。竞争释放假说预测，竞争层次保持不变，但竞争劣势物种能够殖民的差距比优势。然而，PI表明，竞争层次也可能发生变化，有利于适应干扰条件的物种。至少有两种其他的变化机制可能导致这种层次结构的转变：独立于生物效应的非生物环境的改变和邻里大小结构的变化。PI将区分这三种潜在的变化机制，即邻居生物量（去除或存在）、非生物土壤改变（土壤扰动或未扰动）和邻居大小结构（幼年殖民者或成年人）的因子操作。由于这些组件中的每一个的绝对和相对性能的数据将使我们能够比较六个目标物种的反应。初步结果表明，实验设计是能够分离这些影响和物种特征的差距不同的响应组件的变化相比，非差距物种。

9701250 Goldberg In this proposal, the PIs develop a framework to determine the mechanisms of species compositional change following the creation of a gap. It is critical that we learn the mechanistic basis for these changes to understand the process of, and thereby develop models for, gap dynamics. Release from competition due to reduction of neighbor biomass has been the assumed, but largely untested, mechanism responsible for species compositional change in disturbances. The competitive release hypothesis predicts that the competitive hierarchy remains unchanged but competitive inferior species are able to colonize a gap faster than the dominants. However, the PIs suggest that the competitive hierarchy may also shift in favor of species adapted to disturbed conditions. At least two other mechanisms of change could cause this shift in hierarchy: alterations in the abiotic environment independent of biotic effects and changes in neighborhood size-structure. The PIs will separate these three potential mechanisms of change in factorial manipulations of neighbor biomass (removed or present), abiotic soil alteration (soil disturbed or undisturbed) and neighborhood size-structure (juvenile colonists or adults). Data on the absolute and relative performance due to each of these components will allow us to compare the responses of six target species. Preliminary results suggest that the experimental design is able to separate these effects and that species characteristic of gaps respond differently to components of change compared to non-gap species.