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

2013年9月，一场史无前例的暴雨导致科罗拉多州大范围洪灾。除了生命损失和房屋和道路受损外，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绿背鲑鱼的自然活动范围，对供水和娱乐非常重要。鉴于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、溪藻和溪流食物网的影响。目前对洪水的兴趣为开展与洪水安全意识、气候变异性和河流生态系统中干扰的作用有关的外联活动提供了机会。许多科罗拉多州居民，特别是学龄儿童，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，扩大他们针对教师的专业发展研讨会，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人员了解2013年洪水对河流生态系统的短期和长期影响。2013年洪水提供了一个独特的机会，可以研究严重和罕见的干扰事件的影响，这些事件超出了推动河流群落聚集的选择性力量的正常范围。通过将河流地貌(例如，河床移动、河岸干扰的量化)和河流生态学(例如，测量附生植物和底栖动物消费者的生物量和产量，根据稳定的同位素比率估计营养位置和基本食物资源)的方法相结合，研究人员将检验这一假设，即严重洪水干扰的影响是由与洪水有关的河流地貌的变化驱动的。具体地说，该项目测试了一种假设，即河岸地带和分水岭山坡发生变化的溪流将显示洪水对跨营养层的碳和能量流动的长期影响，而群落将在洪水干扰后迅速恢复，洪水干扰只影响溪流河道中的表层沉积物。该项目还测试了河流生态系统可伸缩生态系统模型的一般性，该模型可作为研究不同生态系统间干扰的模板。初步野外研究表明，泥沙输送和河床稳定性的改变减少了某些地点的附生植物的产量，这表明洪水引起的结构变化在重新定居发生很长一段时间后对较高的营养水平具有级联效应。除了量化严重洪灾后第一年生态系统过程的恢复情况外，拟议的研究还将为这些严重洪灾河流恢复的长期研究提供基础。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，站点跨越与2013年9月极端降水相关的一系列干扰强度。调查人员对圣弗拉恩河和南普拉特河的其他支流进行了一系列水文条件的广泛研究，从而为2013年的洪水提供了一个重要的参考点。

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.