Influence of Stream Characteristics and Grazing Intensity on Stream Temperatures211 in Eastern Oregon

摘要

Stream temperatures were measured during summer months, 1978 to 1984, at 12211u001eforested watersheds near John Day, Oregon. to determine temperature 211u001echaracteristics and assess effects of three range management strategies of 211u001eincreasing intensity. Maximum temperatures in streams of the 12 watersheds ranged 211u001efrom 12.5 go 27.8 deg C. Maximum stream temperatures on four watersheds exceeded 211u001e24 deg C, the recommended short-term maximum for rainbow trout (Oncorhynchus 211u001emykiss) and chinook salmon (O. tshawytscha). Streams with greater than 75 percent 211u001estream shade maintained acceptable stream temperatures for rainbow trout and 211u001echinook salmon. Lowest temperatures were observed in streams from ungrazed 211u001ewatersheds. Although highest temperatures were observed in the most intensively 211u001emanaged watersheds (2.8 hectares per animal unit month), the effect of range 211u001emanagement strategy was not definitive. It was confounded by watershed 211u001echaracteristics and about 100 years of grazing use prior to initiation of this 211u001estudy.