| 英文摘要: | 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. |