DISSERTATION RESEARCH: Putting the Relationship Between Species Diversity and Ecosystem Functioning into Context.

随着全球物种灭绝的速度迅速增加，科学家们正在激烈地争论是否需要高度的物种多样性来维持对生态系统功能至关重要的生态过程（如初级生产力，分解和营养循环）。有限的证据表明，某些类型的生态系统可能需要比其他生态系统更多的物种。例如，最近的实验工作导致了这样一种假设，即在以周期性干扰为特征的生态系统中，物种多样性的减少比在不太以干扰为特征的生态系统中物种多样性的减少导致更大的生态过程变化。目前的研究将测试这一假设有关的物种多样性的3个生态过程中的流生态系统，不同的洪水制度（=干扰度量）的速率。根据美国地质调查局的记录，美国东部200条随机选择的河流将根据其频率和河岸洪水的可预测性进行排名。25个流最具特点的洪水和25个流最不具有特点的洪水将被采样，以确定三个生态过程（初级生产力，叶分解，从水中去除悬浮颗粒）的速率，以及影响这些过程的物种的多样性（初级生产者，无脊椎动物食草动物，无脊椎动物滤食性动物）。为了检验这一假设，（1）藻类多样性和初级生产力之间的关系，（2）无脊椎动物食草动物的多样性和叶分解，（3）无脊椎动物滤食性多样性和悬浮颗粒物的保留，将统计比较流之间的洪水和最少的特点。研究结果将有助于确定物种多样性对保护自然或人为干扰的生态系统中的生物过程是否更重要。这项研究还将提供急需的基本信息，了解可能调节物种多样性对生态系统一级进程的贡献的因素。

With the rate of global species extinction rapidly increasing, there is an intensifying debate among scientists as to whether or not a high diversity of species is required to maintain ecological processes that are important for the functioning of ecosystems (processes like primary productivity, decomposition, and the cycling of nutrients). Limited evidence suggests that the certain types of ecosystems may require more species than others. For example, recent experimental work has led to the hypothesis that decreasing species diversity in ecosystems characterized by periodic disturbances leads to greater changes in ecological processes than decreasing species diversity in ecosystems less characterized by disturbance. The current research will test this hypothesis by relating species diversity to the rates of 3 ecological processes in stream ecosystems that differ in flooding regime (=disturbance metric). Using records from the US Geological Survey, 200 randomly selected streams from the eastern United States will be ranked according to their frequency and predictability of bank-full flooding. The 25 streams most characterized by flooding and 25 streams least characterized by flooding will be sampled to determine the rates of three ecological processes (primary productivity, leaf decomposition, and removal of suspended particles from the water), and the diversity of species that influence these processes (primary producers, invertebrate detritivores, and invertebrate filter feeders). To test the hypothesis, the relationships between (1) algal diversity and primary productivity, (2) invertebrate detritivore diversity and leaf decomposition, and (3) invertebrate filter-feeder diversity and retention of suspended particulate matter, will be statistically compared between streams most and least characterized by flooding. The results will help determine whether species diversity is more or less important for conserving biological processes in ecosystems that are naturally or anthropogenically disturbed. This study will also provide much needed, basic information about the factors that potentially regulate the contribution of species diversity to ecosystem-level processes.