RAPID - Quantifying the effects of a catastrophic flood on ecosystem components of Colorado mountain streams

2013年9月，一场前所未有的暴雨在科罗拉多州造成了大面积的洪水。除了生命损失、房屋和道路受损外，洪水还对河流生态系统造成了严重干扰。这些生态系统包括濒临灭绝的赤喉鳟鱼的自然栖息地，对水的供应和娱乐都很重要。考虑到气候变暖导致极端降水事件的频率预计会增加，了解2013年洪水对河流生态系统的影响尤为重要。该项目将评估2013年洪水对河床、河流藻类和河流食物网的影响。目前对洪水的兴趣为与洪水安全意识、气候变化和河流生态系统干扰的作用有关的推广活动提供了机会。许多科罗拉多州居民，尤其是学龄儿童，仍然对未来极端降水和洪水的风险深感担忧。调查人员将与博尔德市保持清洁伙伴关系合作，扩大其教师专业发展讲习班，以便与当地教师和学生分享他们对洪水的研究成果和洪水安全信息。该项目还将帮助科学家和管理者了解2013年洪水对河流生态系统的短期和长期影响。2013年的洪水为研究严重和罕见的干扰事件的影响提供了一个独特的机会，这些事件超出了驱动河流群落聚集的正常选择性力量范围。通过结合河流地貌学（例如，河床运动的量化，河岸扰动）和河流生态学（例如，对周围植物和底栖动物消费者的生物量和产量的测量，从稳定同位素比率估计营养地位和基础食物资源）的方法，研究人员将检验严重洪水扰动的影响是由与洪水相关的河流地貌变化驱动的假设。具体来说，该项目测试了这样一个假设，即河岸带和分水岭山坡被改变的河流将显示出洪水对碳和能量在营养水平上的流动的长期影响，而社区将在洪水干扰后迅速恢复，仅影响河道中的表面沉积物。该项目还测试了河流生态系统的伸缩生态系统模型的普遍性，该模型可以作为研究不同生态系统干扰的模板。初步的野外研究表明，沉积物的迁移和河床稳定性的改变减少了一些地方的周围植物产量，这表明洪水引起的结构变化在再定殖发生后很长一段时间内对更高的营养水平产生了级联效应。除了量化严重洪水后第一年生态系统过程的恢复外，拟议的研究将为这些严重洪水河流恢复的长期研究奠定基础。工作假设将在科罗拉多州南普拉特河支流的多个地点进行测试，这些站点跨越了与2013年9月极端降水相关的扰动强度范围。调查人员对St. Vrain Creek和South Platte River的其他支流进行了广泛的水文条件研究，从而为2013年的洪水提供了重要的参考点。

A rainstorm of unprecedented magnitude caused widespread flooding in Colorado during September, 2013. In addition to loss of life and damage to homes and roads, the flooding caused severe disturbance to stream ecosystems. These ecosystems include the natural range of the endangered greenback cutthroat trout and are important for water supplies and recreation. Understanding the consequences of the 2013 flood on stream ecosystems is particularly important given the expected increases in the frequency of extreme precipitation events as a result of climate warming. This project will assess the impacts of the 2013 flood on stream beds, stream algae, and stream food webs. Current interest in the flood presents an opportunity for outreach activities related to flood-safety awareness, climate variability, and the role of disturbance in stream ecosystems. Many Colorado residents, especially school age children, remain deeply concerned about the future risk of extreme precipitation and flooding. The investigators will work with the City of Boulder Keep it Clean Partnership to expand their professional development workshop for teachers, in order share the results of their research on the flood and information on flood safety with local teachers and their students. This project also will help scientists and managers understand the short-term and long-term effects of the 2013 flood on stream ecosystems.The 2013 flood offers a unique opportunity to study the effects of severe and infrequent disturbance events that are outside the normal range of selective forces driving assembly of stream communities. By combining approaches from fluvial geomorphology (e.g., quantification of bed movement, riparian disturbance) and stream ecology (e.g., measurements of biomass and production for periphyton and benthic consumers, estimates of trophic position and basal food resources from stable isotope ratios), the investigators will test the hypothesis that the effects of severe flood disturbance are driven by changes in stream geomorphology associated with flooding. Specifically, the project tests the hypothesis that streams in which riparian zones and watershed hillslopes are altered will show long-lasting effects of the flood on flow of carbon and energy across trophic levels, whereas communities will recover rapidly following flood disturbance that affected only surface sediments in the stream channel. The project also tests the generality of the Telescoping Ecosystem Model for stream ecosystems, which could serve as a template for the study of disturbance across diverse ecosystems. Preliminary field studies indicate that sediment transport and alteration of bed stability have reduced periphyton production at some locations, suggesting that flood-induced structural changes have cascading effects on higher trophic levels long after recolonization occurs. In addition to quantifying recovery of ecosystem processes during the first year following severe flooding, the proposed research will provide a foundation for long-term studies of recovery in these severely flooded streams. The working hypotheses will be tested at multiple locations on tributaries of the South Platte River in Colorado, at stations that span a range of disturbance intensity associated with the extreme precipitation in September, 2013. St. Vrain Creek and other tributaries of the South Platte River have been studied extensively by the investigators over a range of hydrologic conditions, thus providing an important point of reference for the 2013 flood.