RUI: Bottom-Up and Top-Down Influences on Processing Chain Interactions in Detritus-Based Communities

项目摘要：RUI：自下而上和自上而下对腐质生物群落加工链相互作用的影响腐质是许多生物群落的主要食物来源，腐质动物通过分解和消耗死去的有机物提供生态系统服务。凋落叶是这些以碎屑为基础的群落的主要能量输入，并形成了一个加工链的基础，在这个过程中，树叶会随着时间的推移而腐烂，消费者会专注于不同状态的资源。一些被称为“加工者”的腐食动物可能会通过分解有机物质，将其从整片叶子变成更小的颗粒，从而促进其他腐食动物的生存。这种加工链的相互作用可以通过增加可供消费的资源类型来增加物种的多样性。本研究的目的之一是了解资源加工如何调节社区结构。自下而上和自上而下的力量也可能影响资源和加工链。自下而上的影响，如凋落叶的数量，可能决定加工链的相互作用是促进性的还是竞争性的，以及它们对其他消费者的影响有多大。自上而下的力量，例如顶级捕食者，可能会影响单个消费者，或者通过对处理器产生不利影响而间接影响处理速度。本研究将确定自下而上和自上而下对树洞（一种基于碎屑的食物网模型）加工链相互作用的相对优势。充满水的树洞是易于操纵的小型分解者群落，并且包含处理链相互作用。野外中观和自然生境实验将用于确定当资源、加工者密度和捕食者的存在系统变化时对腐食动物群落和加工链的影响。需要测量的变量包括凋落叶颗粒大小分布的变化、昆虫种类的密度和多样性以及微生物的多样性。需要测试的假设有：1)加工链相互作用和加工者增加了树洞内资源的多样性和丰度，从而影响了其他腐食昆虫和微生物的多样性和丰度；2)资源有限时，加工者对腐食动物多样性和丰度的正向影响大于资源丰富时，3)顶级通才捕食者会减少腐食动物之间的竞争，降低加工者的影响。并影响物种丰富度。了解自下而上和自上而下因素对碎屑加工和加工链的相对优势，将有助于更全面地了解这些因素如何影响群落结构和功能。

Project Abstract: RUI: Bottom-Up and Top-Down Influences on Processing Chain Interactions in Detritus-Based CommunitiesDetritus is the major food source for many communities of organisms, and detritivores provide an ecosystem service by breaking down and consuming dead organic matter. Leaf litter is the primary energy input to several of these detritus-based communities and forms the basis of a processing chain, where leaves decay over time and consumers specialize on resources in different states. Some detritivores, called processors, may facilitate other detritivores by breaking down organic matter and changing it from whole leaves to smaller particles upon which other detritivores feed. This processing chain interaction may increase the diversity of species by increasing the types of resources available for consumption. One objective of this research is to understand how processing of resources regulates community structure. Bottom-up and top-down forces may also influence resources and processing chains. Bottom-up influences, such as the amount of leaf litter, may determine whether processing chain interactions are facilitative or competitive, and how strongly they affect other consumers. Top-down forces, such as top predators, may affect individual consumers, or indirectly affect the rate of processing by adversely affecting processors. This research will determine the relative strengths of bottom-up and top-down influences on processing chain interactions in treeholes, a model detritus-based food web.Water-filled treeholes are small decomposer communities that are easily manipulated and contain processing chain interactions. Field mesocosm and natural habitat experiments will be used to determine the effects on detritivore communities and processing chains when resources, processor density, and presence of predators are systematically varied. Variables to be measured include changes in particle size distribution of leaf litter, the density and diversity of species of insects, and the diversity of microbes. The hypotheses to be tested are: 1) processing chain interactions and processors increase the diversity and abundance of resources in treeholes, which influences diversity and abundance of other detritivorous insects and microbes, 2) processors have a greater positive impact on diversity and abundance of detritivores when resources are limiting than when resources are abundant, and 3) a top generalist predator will decrease competition amongst detritivores, decreasing the impact of the processors, and affecting species richness. Understanding the relative strengths of bottom-up and top-down factors on detrital processing and processing chains will lead to a more complete understanding of how those factors affect community structure and function.