Potential Effects of Thinning in Riparian Forests

Riparian thinning is a restoration technique used to promote canopy growth, increase potential for future large wood recruitment to streams, and promote structural diversity in riparian forests. Riparian thinning may also result in short-term reductions in shade, which can contribute to increases in stream temperature, but other hydrologic and geomorphic factors also play important roles. Increasing stream temperatures can detrimentally affect aquatic organisms adapted to colder temperatures. In the Pacific Northwest, stream temperature is of particular concern for federally listed salmon. In a new study, USGS scientists and USFS collaborators are using remote sensing, modeling, and field studies to evaluate the potential effects of riparian forest thinning on stream temperature in western Oregon. Estimates of shade taken in the field are being compared to estimates obtained from remote sensing techniques, such as lidar, and model predictions. Researchers are also investigating potential effects of hydrologic and geomorphic processes in relation to stream temperatures. Results will be useful to land managers charged with conservation and recovery of salmon, stream habitats, and riparian forests.