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

9701250戈德堡在这项建议中，私人投资倡议发展了一个框架，以确定在形成林隙后物种组成变化的机制。至关重要的是，我们要了解这些变化的机制基础，以了解差距动态的过程，从而开发出差距动态模型。由于邻近生物量减少而导致的竞争释放一直被认为是干扰中物种组成变化的机制，但在很大程度上尚未得到验证。竞争性释放假说预测，竞争等级保持不变，但竞争性劣势物种能够比优势物种更快地殖民缺口。然而，PI表明，竞争等级也可能发生变化，有利于适应受干扰条件的物种。至少还有另外两种变化机制可以导致这种等级的变化：独立于生物效应的非生物环境的变化和邻里大小结构的变化。PIs将分离相邻生物量(移除或存在)、非生物土壤变化(土壤扰动或未扰动)和邻域大小结构(幼年殖民者或成年)因素控制中的这三种潜在的变化机制。关于这些成分的绝对和相对表现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，实验设计能够分离这些影响，与非林隙物种相比，林隙物种特征对变化成分的反应不同。

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.