COARSE WOODY DEBRIS AND SOIL RESPIRATION IN A CLEAR-CUT ON THE OLYMPIC PENINSULA, WASHINGTON, USA

Coarse woody debris (CWD) and soil respiration rates were measured usi ng soda lime traps on a clearcut site in the Hoh River Valley on the w est side of the Olympic Peninsula, Washington. The influence of specie s of CWD (western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Dougla s-fir (Pseudotsuga menziesii (Mirb.) France)), decay class, and log di ameter on respiration rates was determined. CWD and soil respiration w ere measured every 4 weeks from October 1991 to November 1992 along wi th CWD and soil temperature and moisture contents. Western hemlock log s respired at a significantly higher rate (4.05 g CO(2)m(-2). day(-1)) than Douglas-fir logs (2.94 g CO(2)m(-2). day(-1)). There were no sig nificant differences between respiration rates for decay classes 1-2, 3, and 5 logs (4.47, 3.69, and 4.28 g CO(2)m(-2). day(-1), respectivel y), and there was no strong relationship between CWD respiration rate and log diameter. The highest average respiration rate was from the so il in the clearcut (5.22 g CO2 . m(-2). day(-1)). Averaged for the yea r, log and soil respiration rates in the clearcut site were similar to those in an adjacent old-growth forested site. However, seasonal fluc tuations were greater on the clearcut site. Higher summer respiration rates and lower winter rates observed on the clearcut relative to the old-growth site appeared to be driven more by temperature than by mois ture. Clear-cutting also resulted in higher summer CWD and soil temper atures and lower winter temperatures compared with the old-growth site .