The effects of gaps in riparian forest cover on abiotic stream conditions in the southern Appalachians

Abstract

We quantified longitudinal geomorphic and water temperature changes along stream reaches that included a gap in riparian forest cover, hypothesizing that streams would be narrower and warmer within the gaps. We also evaluated and quantified downstream persistence of these changes after the stream returned to forested riparian conditions. We conducted physical habitat surveys of 12 wadeable streams with gaps within and near the Upper Little Tennessee River Basin in western North Carolina and northeastern Georgia. Basin areas ranged from 74 to 6913 hectares and bankfull channel widths varied from 3.4 to 16.4 meters. Stream temperatures were collected using HOBO data loggers for two weeks at fifteen minute intervals. We conducted a statistical evaluation of the sensitivity of stream temperatures to riparian conditions and landscape factors. Temperature responses to gaps varied widely, likely due to differences in elevation, channel width, azimuth, and time of summer. Reach-scale differences in channel form could be observed, matching previous research on riparian forest removal as it relates to channel form. Smaller streams appear to be more sensitive to riparian forest gaps. This information may be useful to land managers and landowners considering riparian forest restoration in a region where many stream segments lack forested riparian zones.