Influences of Windthrow in Forested Stream Buffers

Abstract

Forestry operations have long been understood to contribute to non-point source pollution. With the implementation of federal regulations to thwart such pollution and protect water quality, North Carolina adopted rules called Forest Practice Guidelines (FPGs). This research assesses the efficacy of a specific FPG called Streamside Management Zones (SMZs) for the North Carolina Forest Service (NCFS). Specifically, it examines whether SMZ characteristics influence tree windthrow and if such changes are related to differences in total suspended solids (TSS) levels in North Carolina Piedmont streams. Our results indicate that windthrow is more common in SMZs than in unharvested forest stands. We found that drivers of windthrow vary by location; slope, aspect, and distance to stream contribute to both increased and decreased probability of windthrow. Results also indicate differences in windprone species across sites, but similarities in windfirm species across sites. The majority of sites experienced greater windthrow of larger diameter trees. These results will help to inform the direction of future research conducted by the NCFS and to help develop guidance surrounding FPGs in North Carolina.