Direct and Indirect Effects of Resource Manipulation on Structure and Function of a Longitudinally-linked Ecosystem

这项研究将检验河流中的群落结构和生态系统过程受到资源基础的强烈影响的概念，并评估河流上下游联系的优势。研究人员将通过检查三年内将异地落叶排除在北卡罗来纳州考韦塔水文实验室森林分水岭的源头溪流中的影响来做到这一点。这种操作将使他们能够检查有机质、现成作物、食物质量和底栖群落结构的变化，以应对资源的减少以及生态系统过程中的变化，如有机质运输和养分动态。它还将使他们能够评估营养物质和溶解有机碳(DOC)的外部来源和“新”来源(例如来自每年的垃圾)与内部和“旧”来源(例如来自储存的有机物质的淋溶)之间的相对重要性。研究人员拥有本研究中建议测量的许多参数的操纵流和参考流的七年前处理数据，并为其他参数提出了额外的前处理年。这项研究评估了为河流生态系统拟议的两个重要联系：1)主要的水陆联系(凋落物输入)将被严重削减，2)将评估在受操纵的集水区正下方的河流段(恢复区)的上下游联系，涉及底栖无脊椎动物、颗粒和溶解有机物质的运输。

This study will test the concepts that community structure and ecosystem processes in streams are strongly influenced by the resource base and assess the strengths of upstream-downstream linkages in streams. The investigators will do this by examining the effects of excluding allochthonous leaf litter for three years from a headwater stream draining a forested watershed at Coweeta Hydrological Laboratory, North Carolina. This manipulation will allow them to examine changes in organic matter standing crop, food quality, and benthic community structure in response to the decrease in resources and accompanying changes in ecosystem processes such as organic matter transport and nutrient dynamics. It will also allow them to assess the relative importance of external and "new" (e.g. from annual litterfall) vs. internal and "old" (e.g. from leaching of stored organic matter) sources of nutrients and dissolved organic carbon (DOC). The investigators have seven years of pretreatment data for both the manipulated and reference streams for many of the parameters proposed to be measured in this study and propose an additional pretreatment year for other parameters. This study assesses two important linkages proposed for stream ecosystems: 1) major aquatic- terrestrial linkages (litter inputs) will be severely curtailed, and 2) the upstream-downstream linkage in a stream segment (recovery zone) immediately below the manipulated catchment will be assessed with respect to benthic invertebrates, particulate and dissolved organic matter transport.