Influence of grazing on channel morphology of intermittent streams
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Authors: M. R. George, R. E. Larsen, N. K. McDougald, K. W. Tate, J. D. Gerlach, and K. O. Fulgham
Date: 2002
Journal: Journal of Range Management
Volume: 55
Number: 6
Pages: 551-557
Summary of Methods: Changes in stream channel morphology due to grazing were examined in a riparian grazing study conducted at the San Joaquin Experimental Range (SJER) in Madera County, California (37° 05' N, 169° 45' W). Five grazing treatments (no grazing, wet season-moderate, wet season-high concentration, dry season-moderate, dry season-high concentration) were applied using mature beef cows on three intermittent streams. Wet season grazing occurred from February to May, and dry season grazing ran from July to October. Supplements were used to lure animals to achieve concentration treatments when necessary. Utilization was measured through stubble heights. Changes in stream channel were monitored by measuring width and depth along stream channel cross-sections.
Article Summary / Main Points: Study detected no streambank erosion. Control treatment resulted in increased channel depth over the four years of the study. No other changes were observed in channel width, distance to right and left bank, maximum depth, mean depth, cross sectional area, and width to depth ratio when averaged across years for any treatments. There were yearly effects to stream morphology but they were not consistent from year to year or treatment to treatment.
Vegetation Types: California Grasslands (including all annual grasslands) Riparian and Wetlands
MLRA Ecoregions: 18 Sierra Nevada Foothills 22A Sierra Nevada Mountains
Agrovoc Control Words: Riparian zones Grazing Streams
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: grazing effects, streambank erosion, sediment, annual rangelands, california
Annotation: This study found no evidence of erosion due to grazing treatments in the time frame that they conducted the research. The yearly variation that was experienced could be due to natural variation in stream flow dynamics. The well drained, coarse sands found in the research area may provide more resistance to streambank erosion when compared with fine textured soils. In addition, they are considered slower to respond to removal of grazing, possibly requiring longer time frames to allow for system recovery. More research is necessary to separate natural variation from management induced disturbance.
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