Coarse woody debris respiration of Japanese red pine forests in Korea: controlling factors and contribution to the ecosystem carbon cycle

Coarse woody debris (CWD) respiration (R_CWD) has strengths in efficient investigation of CWD decomposition rate and application into studies on ecosystem carbon (C) processes. Here, R_CWD was investigated in two Japanese red pine forests to determine its response to environmental factors and CWD properties, and its contribution to the ecosystem C budget. Samples were collected based on CWD position (log or snag), species (pine or deciduous), and decay class in the Gwangneung pine forest (GPF) and the Mt. Jumbong pine forest (JPF), Korea. R_CWD was measured at different incubation temperatures using a closed chamber system. Annual R_CWD was estimated by developing and applying air temperature–R_CWD regressions to air temperature data. In the GPF, annual estimated R_CWD (g C kg⁻¹ year⁻¹) was 29.54, 3.90, and 158.95 for pine logs, pine snags, and deciduous logs, respectively. In the JPF, R_CWD was 49.09 for pine logs and 14.55 for pine snags. Temperature and CWD moisture were the main drivers of R_CWD. CWD species also influenced R_CWD, possibly by supporting different habitats for microbes and invertebrates. R_CWD in the GPF accounted for approximately 4 % of heterotrophic respiration and 54 % of the CWD decomposition rate. In the JPF, R_CWD was approximately equal to the CWD decomposition rate. R_CWD might constitute a minor portion of the net ecosystem production (4 % in the GPF), because of the relatively high stand productivities and small CWD masses. In the GPF, the major factor influencing R_CWD was mortality, whereas moisture had the greatest influence on R_CWD in the JPF.