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Impact of Deferred Rotation Grazing on Stream Characteristics in Central Nevada: A Case Study
Author(s) -
Myers Thomas J.,
Swanson Sherman
Publication year - 1995
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1995)015<0428:iodrgo>2.3.co;2
Subject(s) - grazing , rotation (mathematics) , environmental science , geography , hydrology (agriculture) , ecology , geology , mathematics , biology , geometry , geotechnical engineering
Three central Nevada streams were selected to study the watershed‐scale effects on stream morphology and bank stability of deferred rotation cattle grazing, complete rest from grazing, and the presence of road crossings. The streams had gravel substrates, and their entrenchments, width : depth ratios, sinuosities and gradients were moderate. Based on statistical analysis of 1980 stream survey results, geologic basin features, and the occurrence of similar flooding, we concluded that the three streams had similar conditions at the start of the grazing treatment. Since 1980, deferred rotation grazing allowed much improvement of aquatic and riparian habitats but the improvement was limited by the presence of roads, which apparently added sediment to the streams. Complete rest from grazing without the presence of roads allowed the most improvement. Of the variables measured in the 1980 survey, streambank soil stability, type and amount of vegetation cover, and quality of pools improved most in all three streams. The best values for channel and water width : depth ratios, channel entrenchment, bank angle, bank undercut, and bank depth were measured on the stream managed with complete rest. Deferred rotation grazing in the absence of roads produced the second best values. The ratio of channel width to base flow water width was significantly higher on bare ground transects. Shrub and tree cover increased significantly more on the rested than on the grazed watersheds. These results should help managers select aquatic habitat and stream morphology objectives for grazing management.