Abstract Identifying and understanding functional process domains (sensu Montgomery, 1999 ) in rivers is paramount for linking the physical habitat template to ecosystem structure and function. To date, efforts to do this have been rare, especially in large rivers, as they require appropriate tools for quantifying habitat heterogeneity with fine-scale resolution across broad spatial extents. In this study, we used side-scan sonar technology to map riverbed substrate at six sites in the Yellowstone and Missouri rivers. Substrate maps were then analyzed and visualized using geospatial analysis to relate fine-grained spatial substrate patterns to process domain structure. Our findings revealed two distinct nested domains of substrate patchiness, suggesting that different factors are responsible for shaping patterns of substrate at different scales. Although small-scale patchiness in substrate was likely driven by internal, or autogenic, physical processes, patterns at larger segment extents (>3 km) were often driven by abrupt transitions in habitat related to exogenous factors such as lateral erosion of talus, tributary inputs, and bank armoring. Additionally, we found that heterogeneity in benthic substrate increased with spatial extent at all of our study sites; however, this relationship was lower in the Missouri River, which is altered by impoundment. Our study represents one of the first efforts to relate benthic habitat heterogeneity to nested process domain structure in large riverscapes, and offers a unique perspective for linking landscape processes, geomorphological habitat heterogeneity, and biological structure and function in large rivers.

中文翻译：

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揭示大河流中的过程域：两个北美河流景观中底栖基质异质性的模式和潜在驱动因素

摘要 识别和理解河流中的功能过程域（sensu Montgomery，1999 年）对于将物理栖息地模板与生态系统结构和功能联系起来至关重要。迄今为止，这样做的努力很少见，特别是在大河流中，因为它们需要适当的工具来量化栖息地异质性，并在广泛的空间范围内具有精细的分辨率。在这项研究中，我们使用侧扫声纳技术绘制了黄石河和密苏里河六个地点的河床底物图。然后使用地理空间分析对基底图进行分析和可视化，以将细粒度空间基底模式与处理域结构相关联。我们的研究结果揭示了底物斑块的两个不同嵌套域，表明不同因素负责在不同尺度上塑造底物模式。虽然基质中的小规模斑块可能是由内部或自生的物理过程驱动的，但较大段范围（> 3 公里）的模式通常是由与外源因素相关的栖息地突然转变驱动的，例如距骨的侧蚀、支流输入和银行装甲。此外，我们发现底栖底物的异质性随着我们所有研究地点的空间范围而增加；然而，这种关系在密苏里河中较低，它被蓄水改变了。我们的研究代表了将底栖栖息地异质性与大河流景观中的嵌套过程域结构联系起来的首批努力之一，并为将大河流中的景观过程、地貌栖息地异质性以及生物结构和功能联系起来提供了独特的视角。