Stream canopy and its relationship to salmonid biomass in the Intermountain West
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Authors: W. S. Platts, and R. L. Nelson
Date: 1989
Journal: North American Journal of Fisheries Management
Volume: 9
Number: 4
Pages: 446-457
Summary of Methods: Seventeen study sites under rest-rotation grazing systems in Idaho, Nevada, and Utah were used to determine the relationships between canopy cover, salmonid biomass and livestock grazing over four year period. Canopy density, light intensity, unobstructed sun arc and average potential daily thermal input variables in grazed and ungrazed (rested) portions of each stream were measured. These variables were correlated with salmonid biomass, geographic regions, and grazed and ungrazed pastures.
Article Summary / Main Points: The best overall predictor of salmonid biomass per unit volume was unobstructed sun arc which is correlated with thermal input (i.e., an increase in sun arc increases thermal unit). In the Great Basin, thermal input was a better predictor of salmonid biomass per unit than in the Rocky Mountains. Although most average canopy attributes were not considerably different between grazed and ungrazed study sites, canopy density was 60% greater and potential thermal input was 12% less on ungrazed sites than grazed sites. Average thermal input was slightly greater in rested sites than grazed sites, but the difference was small (6%) on Otter, Chimney, and Tabor creeks where canopy density was higher and thermal input was lower on grazed sites.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 25 Owyhee High Plateau 43B Central Rocky Mountains 47 Wasatch and Uinta Mountains
Agrovoc Control Words: Riparian zones Grazing Inland Fisheries
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: salmonid biomass, stream canopy, light intensity, thermal input, canopy density
Annotation: This was a replicated study over four years and is applicable to riparian areas across the western USA. Grazing strategies, timings, and intensities of forage use were evaluated in multiple states (17 study sites) in a long-term nature; strengthening this study(s) findings. Additionally, Platts and Nelson (1985, N. Amer. J. Fish. Manage. 5:547-556; 1985, J. Soil and Water Cons. 49:374-379; 1985, Rangelands 7:5-7; and 1985, Rangelands 7:7-10) studied rangeland utilization along riparian areas in Idaho, Nevada, and Utah; also available on the RSIS website.
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