Effects of Disturbance and Spatial Heterogeneity on Nutrient Retention and Transport in a Stream-Riparian Ecosystem

9306909费舍尔这项研究将确定空间配置对河流-河岸生态系统中营养物质保持的影响。河流是复杂的、非均质的系统，由一条潮湿的河道、湿河道下方和附近的饱和沉积物以及两侧边缘的一条陆地植被(河岸带)组成。其中每一个的范围和形状在空间和时间上都有很大的差异。当水向下游流动时，它会在这些组件之间以不同的程度移动。由于旱地河流具有几个良好的特性，因此将被用作本研究的模式系统。这个项目的总体目标是确定结构如何影响在给定范围内在该水中运输的材料被保留和回收的程度。这一目标将通过解决围绕这项研究组织的四个问题来实现。首先，空间格局是如何影响养分保持的？最初将考虑单个时间点的空间配置及其影响。这将通过绘制河流生态系统的两个尺度来实现，以确定其物理形态，描述这些要素之间的水文联系，以及流动路径对养分保持的影响。将通过实验操作配置，以确定不同图案对保留过程的影响。其次，骚乱是如何影响这段关系的？将研究几个单独的洪涝和干旱事件对事件间配置和系统功能恢复的影响。第三，形态和功能如何在大的空间和时间尺度上相互作用？这项分析将涉及扩大河段尺度的过程，以包括由谷底宽度产生的地貌变化。时间尺度将通过考虑不同洪水和干旱状况的影响；它们的频率、强度和在时间上的分布来完成。第四，北美沙漠溪流在全球范围内对这种生态系统类型的结果有多普遍？这个问题的答案将是对澳大利亚和西班牙类似沙漠溪流之间的模式-过程关系进行比较研究。这项研究具有重要意义，因为它将有助于对复杂生态系统中的模式和过程如何相互作用的基本科学理解。与生态系统生态学中常用的黑匣子、混合良好的反应堆模型相比，它是一个进步。研究成果对应用生态学也有一定的参考价值。河流是连接陆地高地与下游水库、地下水供应或河口的开放系统。河流负荷在运输过程中的保留和转化影响向受水系统输送的水的质量。河岸和其他湿地生态系统越来越多地被用于这种“营养过滤”能力。这项研究的结果将有助于理解自然河流中的这一过程，并在管理和人工设计的系统中对其进行优化。***

9306909 Fisher This research will determine the effect of spatial configuration on nutrient retention in stream-riparian ecosystems. Streams are complex, heterogeneous systems consisting of a wetted channel, saturated sediments below and adjacent to the wetted channel, and a strip of terrestrial vegetation (the riparian zone) at each lateral edge. The extent and shape of each of these varies greatly in space and time. As water flows downstream, it moves to varying degrees among these components. Because of several favorable properties, streams of arid lands will be used as model systems for this study. The overall goal of this project is to determine how configuration affects the extent to which materials transported in this water are retained and recycled within a given reach. This goal will be met by addressing four questions around which the research is organized. First, how does spatial pattern influence nutrient retention? Spatial configuration and its effects will initially be considered for a single point in time. This will be accomplished by mapping the stream ecosystem a two scales to determine its physical configuration, describing hydrologic connections among these elements, and the consequences of flow path for retention of nutrients. Configuration will be manipulated experimentally to determine the effect of different patterns on the retention process. Second, how does disturbance affect this relationship? Several individual flash flood and drought events will be studied in terms of their effect on configuration and recovery of system function between events. Third, how do configuration and function interact over large spatial and temporal scales? This analysis will involve scaling up reach-scale processes to include geomorphic variation generated by valley floor width. Temporal scaling will be accomplished by considering the effect of variable flood and drought regimes; their frequency , intensity, and distribution in time. Fourth, how general are results derived from North American desert streams for this ecosystem type worldwide? This question will be answered with a comparative study of the pattern-process relationship among streams of similar deserts in Australia and Spain. %%% This research is significant in that it will contribute to basic scientific understanding of how pattern and process interact in complex ecosystems. It is an advance over black box, well-mixed reactor models that have been commonly used in ecosystem ecology. Research results will be useful to applied ecology as well. Streams are open systems which link terrestrial uplands with downstream reservoirs, groundwater supplies, or estuaries. Retention and transformation of stream load in transit affects the quality of water delivered to recipient systems. Riparian and other wetland ecosystems are increasingly used for this "nutrient filtration" capacity. Results of this research will aid in understanding this process in natural streams and optimizing it in managed and human-designed systems. ***