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Most climate change research has focused on threats to native species, but non-native, invasive species may be impacted as well. We show that warmer temperatures and shifts from snowmelt runoff regimes to mixed runoff regimes in parts of the Northern Rocky Mountains, US, may reduce the occurrence of nonnative brook trout (Salvelinus fontinalis) and indirectly benefit the native cutthroat trout (Oncorhynchus clarkii). Differences in reproductive strategy may account for the differential responses of the two species. We base these findings on models of species occurrence that use landscape and climatic variables as predictors and are built from a database of >4000 fish collection points. We estimate changes in stream...
Inferences drawn from regional bioassessments could be strengthened by integrating data from different monitoring programs. We combined data from the US Geological Survey National Water-Quality Assessment (NAWQA) program and the US Environmental Protection Agency Wadeable Streams Assessment (WSA) to expand the scope of an existing River InVertebrate Prediction and Classification System (RIVPACS)?type predictive model and to assess the biological condition of streams across the western US in a variety of landuse classes. We used model-derived estimates of taxon-specific probabilities of capture and observed taxon occurrences to identify taxa that were absent from sites where they were predicted to occur (decreasers)...
Forecasting responses of benthic community structure and function to anthropogenic climate change is an emerging scientific challenge. Characterizing benthic species by biological attributes (traits) that are responsive to temperature and streamflow conditions can support a mechanistic approach for assessing the potential ecological responses to climate change. However, nonclimatic environmental factors also structure benthic communities and may mitigate transient climatic conditions, and these must be considered in evaluating potential impacts of climate change. Here we used macroinvertebrate and environmental data for 279 reference-quality sites spanning 12 states in the western US. For each sampling location,...
Ecological thresholds that lead to alternative community states can be exceeded through gradual perturbation or as a result of sudden disturbance. Many Great Plains streams have experienced dramatic changes in their hydrologic regime resulting from water and landuse changes that began as early as 1880. These changes, combined with the presence of many invasive species, have substantially altered the fish communities in this area. We quantified temporal changes in fish communities in 3 large river basins in relation to putative anthropogenic stressors, including increased sediment supply derived from row-crop agriculture (beginning in 1880), habitat fragmentation caused by reservoir construction (beginning in the...
Riparian zones can strongly influence the exchange of nutrients between streams and their watersheds. Most riparian studies have been done in mesic watersheds, which differ significantly from arid-land watersheds hydrologically. The goals of our work were to determine the strength and direction of hydrologic linkages between stream and riparian zone, and to estimate the extent of uptake of streamwater N by riparian trees in Sycamore Creek, a Sonoran Desert stream. Br? and 15NH4+ were added simultaneously to the surface stream to trace water and N from stream to riparian zone. Br? concentrations in riparian wells installed downstream of the release point increased during the addition, demonstrating a strong hydrologic...