Spatial variation in respiration from coarse woody debris in a temperate secondary broad-leaved forest in Japan

Abstract

We measured the rates of respiration from snags and logs (“coarse woody debris”, CWD) of Japanese red pine ( Pinus densiflora Sieb. et Zucc.) to examine the rate of decomposition and CO 2 efflux from these materials in a temperate secondary broad-leaved forest in Japan. At this site, a high quantity of CWD of P. densiflora had accumulated as a result of pine wilt disease during the 1970s. Respiration rates were measured using a dynamic closed chamber method combined with an infrared gas analyzer. We measured the respiration rate of 7 samples of snags and 10 samples of logs from August 2003 to January 2004. The responses of the respiration rates of snags ( R snag) and logs ( R log) to changing temperature were both exponential and the responses to water content were quadratic, and the same function could be used to estimate annual values of both R snag and R log. Intensive measurements of water contents of snags and logs showed a marked difference in water content. The mean water content of snags was 20% of log water content. This difference was likely responsible for the observed difference in annual R snag and R log. The decay rate constants estimated from the respiration rates measurement of snags and logs were 0.019 and 0.081 year −1, respectively. Despite being lower than R log, R snag was a significant compartment of the CWD carbon budget at this site.