STREAMSIDE FOREST BUFFER WIDTH NEEDED TO PROTECT STREAM WATER QUALITY, HABITAT, AND ORGANISMS: A LITERATURE REVIEW

This literature review addresses how wide a streamside forest buffer needs to be to protect water quality, habitat, and biota for small streams (<= similar to 100 km(2) or similar to 5th order watershed) with a focus on eight functions: (1) subsurface nitrate removal varied inversely with subsurface water flux and for sites with water flux > 50 l/m/day (similar to 40% avg base flow to Chesapeake Bay) median removal efficiency was 55% (26-64%) for buffers < 40 m wide and 89% (27-99%) for buffers > 40 m wide; (2) sediment trapping was similar to 65 and similar to 85% for a 10- and 30-m buffer, respectively, based on streamside field or experimentally loaded sites; (3) stream channel width was significantly wider when bordered by similar to 25-m buffer (relative to no forest) with no additional widening for buffers >= 25 m; (4) channel meandering and bank erosion were lower in forest but more studies are needed to determine the effect of buffer width; (5) temperature remained within 2 C of levels in a fully forested watershed with a buffer >= 20 m but full protection against thermal change requires buffers >= 30 m; (6) large woody debris (LWD) has been poorly studied but we infer a buffer width equal to the height of mature streamside trees (similar to 30 m) can provide natural input levels; (7, 8) macroinvertebrate and fish communities, and their instream habitat, remain near a natural or semi-natural state when buffered by >= 30 m of forest. Overall, buffers >= 30 m wide are needed to protect the physical, chemical, and biological integrity of small streams.