Collaborative Research: Leaky Rivers: Nutrient Retention and Productivity in Rocky Mountain Streams Under Alternative Stable States

河流只占地球表面的一小部分，但对于营养物质的运输和加工以及对维持全球生物多样性来说，它们的重要性不成比例。溪流中的堵塞增加了营养物质的保留和鱼类产量。人类清除堵塞在森林生态系统中普遍存在，造成了储存营养物质和生产鱼类的能力有限的“大坝贫困”的溪流。一个最好的例子是落基山脉南部的溪流，那里的木材去除遗产极大地减少了拥堵。这个项目的问题是：堵塞的损失是否会降低源头河流的生产能力？据推测，堵塞的损失会使溪流中的营养物质更容易泄漏，从而减少营养物质的加工和鱼类产量。这个项目将研究河流坡度上的堵塞和与堵塞相关的过程，包括老森林、无人管理的幼林和集约化管理的森林中的河流。这项工作将首次对清除堵塞对河流生态系统的影响进行景观规模的评估。这项研究可以通过将对堵塞历史分布的估计与当代堵塞中密集测量的地球化学和生物变量相结合，改变目前对木材对河流生态系统影响的理解，从而将局部规模的观测扩展到整个蒸汽网络。了解拥堵的损失如何影响河流，将为森林景观中源头河流的资源管理提供信息。国家公园管理局和美国林务局监管着美国西部的大片林地，并试图恢复落基山脉景观的一些推测的历史特征。通过加强对堵塞的变化以及这些结构的生物地球化学和生态影响的了解，拟议的工作将为这些管理行动提供急需的背景。该项目还将为1名博士后学者和4名研究生提供培训。它还将为几名本科生提供研究经验。

Streams occupy a small part of Earth's surface, but are disproportionately important for transport and processing of nutrients and for maintaining global biodiversity. Logjams in streams increase retention of nutrients and fish production. Human removal of logjams is pervasive in forested ecosystems, creating "dam-impoverished" streams with limited capacity to store nutrients and produce fish. A prime example is streams of the southern Rocky Mountains, where a legacy of wood removal has greatly reduced logjams. This project asks: Does the loss of jams reduce the productive capacity of headwater streams? It is hypothesized that the loss of jams makes streams more leaky of nutrients, with subsequent decreased nutrient processing and fish production. This project will examine logjams and jam-associated processes across a gradient of streams, including streams in old-growth forests, unmanaged younger forests, and intensively managed forests. This work will provide the first landscape-scale assessment of the effects of jam removal on stream ecosystems. This research can transform current understanding of wood effects on stream ecosystems by combining estimates of logjam historical distribution with intensively measured geochemical and biological variables in contemporary jams, allowing extension of local-scale observations to entire steam networks. Understanding how the loss of jams affects streams will inform resource management of headwater streams in forested landscapes. The National Park Service and the US Forest Service oversee vast tracts of forested lands in the American West and are attempting to restore some of the inferred historical characteristics of the Rocky Mountain landscape. By enhancing understanding of changes in jams, as well as the biogeochemical and ecological influence of these structures, the proposed work will provide much-needed context for these management actions. This project will also provide training for one post-doctoral scholar and four graduate students. It will also provide research experiences for several undergraduate students.