CAREER: Influence of Geomorphic Complexity on Stream Ecosystem Function

近几十年来，河流生态系统由于人类活动，如水坝建设、农业施肥和城市化等，已经严重退化。这种退化既包括物理变化，即地貌变化，也包括生态变化。评估这些问题的结果和潜在的解决方案不仅需要了解地貌、生态和生物地球化学过程，更重要的是，了解这些过程如何相互作用。该项目将利用水槽、野外和数值模拟实验，对河流地貌形态和过程如何影响生态系统功能（即河流营养保留）进行定量和机制的理解。室外实验水槽将被构建，以检查通道内与水下瞬时储存在营养物质保留中的作用，以及各种地貌参数如何控制这些储存区域，以及河流地貌形式如何影响营养物质的生化保留率。然后，研究将扩展到实地尺度的河道操纵，这将包括对天然河道的流动条件的操纵，以及对河流恢复项目的更实质性的操纵。利用从水槽和实验操作研究中获得的见解，该项目的第二阶段将开发河流生态系统模型的初始组成部分，将现有的地貌和生态模型结合起来，以检查地貌形式和过程以及生态过程如何在一系列空间和时间尺度上相互作用。这个模型将独特地用于探索和发展理论问题。除了研究之外，该项目还将开发一系列教育项目，让7-12年级的学生了解环境科学的空间和定量方面，特别是河流研究。该教育项目将利用现有的环境野外教育项目和现有的中学生普通科学教育推广项目，从而为初高中学生提供更全面的环境教育体验。该教育项目将使用职前教师，为未来具有丰富空间环境分析教育经验的环境教育工作者提供直接来源。随着河流修复的研究和应用的增加，河流和溪流受到广泛的物理和生态干扰的现实启发。该项目将使用一系列实验流操作和数值模拟来发展关于流中物理和生物过程相互交织的基本科学知识。这一知识对于发展对河流生态系统的全面了解至关重要，因为这种了解是有效管理和潜在恢复淡水资源的基础。这个项目的研究也将作为一系列教育课程的基础，旨在教授学生河流的物理和生物过程是如何联系的，这些课程将从研究生水平的研讨会到中学学生的短期课程。

River ecosystems have been severely degraded over recent decades by human activities such as the construction of dams, fertilizer applications from agriculture, and urbanization, to name but a few. This degradation includes both physical, i.e., geomorphic, and ecological changes. Assessing the results of and potential solutions to these problems necessitates understanding not only geomorphic, ecological, and biogeochemical processes, but more importantly, how these processes interact. This project will use flume, field, and numerical modeling experiments to develop a quantitative and mechanistic understanding of how fluvial geomorphic forms and processes influence ecosystem function, namely stream nutrient retention. Outdoor experimental flumes will be constructed to examine the role of in-channel versus hyporheic transient storage in nutrient retention, and how various geomorphic parameters control these storage zones, as well as how fluvial geomorphic forms influence the rates of biochemical retention of nutrients. The research will then be extended to field-scale channel manipulations, which will include both manipulations of flow conditions in natural river channels, as well as the more substantial manipulation of river restoration projects. Using the insight gained from the flume and experimental manipulation studies, the second phase of the project will develop the initial components of a Stream Ecosystem Model, coupling existing geomorphic and ecological models in order to examine how geomorphic forms and processes and ecological processes interact across a range of spatial and temporal scales. This model will be uniquely usable to explore and develop theoretical questions. Beyond research, this project will develop a series of educational programs to expose students, grades 7-12, to spatial and quantitative aspects of environmental science, particularly river studies. The education program will leverage off of an existing environmental field education program and an existing general science education outreach program for middle school students, thus providing a more holistic environmental educational experience for middle school and high school students. The education program will use pre-service teachers, providing an immediate source of future environmental educators with substantial spatial environmental analysis education experience. This research is inspired by the realities of widespread physical and ecological disturbance to rivers and streams along with the increased research and application of river restoration. This project will use a series of experimental stream manipulations and numerical modeling to develop fundamental scientific knowledge of the way physical and biological processes in streams are inter-twined. This knowledge is critical to developing a holistic understanding of stream ecosystems as such understanding is the basis for effective management and potential restoration of freshwater resources. The research during this project will also serve as the basis for a series of educational courses designed to teach students how physical and biological processes in rivers are linked, and these courses will span from graduate-level seminars to short courses for middle-school students.