Effects of Clear-cut Logging on Wood Breakdown in Appalachian Mountain Streams

Red oak (Quercus rubra) sticks, approximately 10-cm long and in three size classes (large, 3-cm diam, 22-55 g; medium, 1-2-cm, 12-22 g; small, < 1-cm, 312 g) were placed at five sites in two second-order streams at Coweeta Hydrologic Laboratory. One stream, Big Hurricane Branch, drains a watershed logged in 1976 (WS 7); the other stream, Hugh White Creek, drains an uncut reference watershed (WS 14). Ten sticks of each size class were collected from each site at 6-month to 1year intervals from September 1981 through November 1985. Calculated breakdown rates ranged from 0.107 to 0.281 y-1. Breakdown rates were significantly different among size classes on both watersheds-smaller sticks lost mass faster than larger sticks. Breakdown rates of similar size sticks were significantly faster in Big Hurricane Branch, the disturbed stream, than in Hugh White Creek. Faster rates of wood breakdown in Big Hurricane Branch may be associated with higher stream N03-N levels, greater stream channel instability and greater invertebrate abundance on sticks.