Effects of Plant Diversity and Functional Characteristics on Species Invasions

几十年来，生态学家们一直假设，物种越多样的群落就越难入侵，因为物种越丰富，留给潜在入侵者的可用资源就越少。本研究试图解决三个基本问题：（1）多样性是否影响群落的可入侵性？(2)入侵者与资源获取相关的功能属性是否影响其入侵的成功？(3)当入侵者与社区成员在与资源捕获相关的功能属性上不同时，入侵成功的可能性是否更大？实验设计允许分离的影响，由于植物组成的差异，由于功能组丰富度的差异的影响。与以往通过调查已经被入侵的群落来推断这些问题的答案的研究不同，该项目将直接测试入侵到植物功能群的组成和丰富程度不同的群落中的模式。它将研究竞争作为一种机制参与入侵结果的作用。这项研究将使用已经建立的实验社区在加州蛇形草原。这些实验社区允许控制几个因素，包括干扰制度，土壤肥力和社区历史，这混淆了试图在已经入侵的生态系统中研究这些问题。通过直接播种那些还不是这些实验群落的一部分，但在当地出现的物种，也将有可能控制繁殖体到达的速度。一旦繁殖体到达，这种控制对于确定是什么限制了入侵的成功至关重要。总体而言，这组实验将提供一个直接的测试有关社区的入侵性及其潜在机制的假设。

9974159HooperEcologists have hypothesized for decades that more diverse communities are more difficult for species to invade because greater species richness should leave less available resources for a potential invader to exploit. This research seeks to address three fundamental questions (1) Does diversity influence invasibility of communities? (2) Do functional attributes of invaders related to resource acquisition influence the success of their invasion? (3) Is there a greater probability of invasion success when the invader differs from community members in functional attributes related to resource capture? The experimental design allows separation of effects due to differences in plant composition from effects due to differences in functional group richness. Unlike previous studies that have inferred answers to these questions by surveying communities which have already been invaded, this project will directly test the patterns of invasion into communities that differ in both composition and richness of plant functional groups. It will study the role of competition as a mechanism involved in invasion outcome. The research will use already-established experimental communities in California serpentine grassland. These experimental communities allow control of several factors, including disturbance regime, soil fertility, and community history, which confound attempts to study these questions in already invaded ecosystems. By directly seeding in species that are not already a part of those experimental communities, but that occur in the local area, it also will be possible to control for the rate of propagule arrival. This control is critical for determining what limits the success of an invasion once propagules have arrived. Overall, this set of experiments will provide a direct test of hypotheses concerning community invasibility and its underlying mechanisms.