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We examined the ability of 5 a priori landscape classifications (3 sizes of catchments, ecoregions, and life zones) to partition observed variation in the composition of stream invertebrate assemblages. Analyses were based on 254 unimpaired sites from montane streams in California and 1912 sites from several regions of the United States. Estimates of classification strength (CS) were used to measure how well classificationsp artitionedv ariationi n compositiona mong sites. CS was measured as the difference between overall weighted mean within-class compositional similarity (V) and mean between-classs imilarity (B). We compared CSs of the 5 a priori classificationsw ith post hoc classificationo f sites based on clustera...
NO3 Uptake in Shallow, Oligotrophic, Mountain Lakes: The Influence of Elevated NO3 Concentrations, credited to Lafrancois, Brenda Moraska, published in 2004. Published in Journal of the North American Benthological Society, volume 23, issue 3, on pages 397 - 415, in 2004.
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)...
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...