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

本研究将检验河流中群落结构和生态系统过程受资源基础强烈影响的概念，并评估河流上下游联系的优势。在北卡罗莱纳州Coweeta水文实验室，研究人员将通过在三年内从排水森林流域的水源中排除外来凋落叶的影响来实现这一目标。这种操作将使他们能够检查有机质常产作物、食品质量和底栖生物群落结构的变化，以响应资源的减少和伴随的生态系统过程的变化，如有机质运输和营养动态。它还将使他们能够评估外部和“新”（例如，每年的凋落物）与内部和“旧”（例如，从储存的有机物的浸出）的营养来源和溶解的有机碳（DOC）的相对重要性。研究人员有7年的预处理数据，包括本研究中拟测量的许多参数的操作流和参考流，并建议对其他参数进行额外的预处理。本研究评估了河流生态系统的两个重要联系：1)主要的水生-陆地联系（凋落物输入）将被严重削弱；2)在操纵集水区下方的河流段（恢复区）的上下游联系将被评估，涉及底栖无脊椎动物、颗粒和溶解有机物的运输。

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.