Duration of stream temperature increases following forest cutting in the Southern Appalachian Mountains
Cutting timber along small streams in the southern Appalachian Mountains increases water temperature. Although the effect is assumed to be short-lived because of rapid regrowth of dense vegetation, timber harvest in streamside shade zones on National Forest land is carefully regulated to minimize temperature changes and maintain trout habitat. Clearcutting all vegetation over 2.5 cm DBH from a 59.6-ha south-facing watershed in western North Carolina allowed both the magnitude and duration of water temperature increases to be studied. About 958 m of stream were exposed. Daily maximum temperatures at the downstream margin of the cutting were increased an average of 3.3°C the first two summers after cutting. The increases declined in the next three summers to 1.2°C. Daily minimums were increased about 1.3°C both winter and summer, but only in the first year. The daily range of water temperatures (maximum minus minimum) was increased during all five summers. A method for predicting water temperature changes was tested and found to overestimate the summer increases.