Feedback of soil organic carbon decomposition to artificial soil warming

土壌有機炭素分解の人工的な温暖化に対するフィードバック

寺本 宗正*; 近藤 俊明*; Liang, N.*; Zeng, J.*; 中根 周歩*; 小嵐 淳   ; 安藤 麻里子  

Teramoto, Munemasa*; Kondo, Toshiaki*; Liang, N.*; Zeng, J.*; Nakane, Kaneyuki*; Koarashi, Jun; Atarashi-Andoh, Mariko

Globally, soil contains around 3,000 GtC of soil organic carbon (SOC). SOC is decomposed by soil microbiota, and CO is released to the atmosphere (heterotrophic respiration, Rh). Global annual Rh is estimated as 51-57 GtC, and this large CO efflux increases exponentially along with temperature rise. Therefore, it is possible that global warming increases Rh, and the increased Rh further accelerates global warming (positive feedback). To examine the long-term feedback of SOC decomposition to global warming in Asian monsoon forest region, we set multi-channel automated chamber and artificial warming system in a warm-temperate evergreen broad-leaved forest in Higashi Hiroshima, western Japan, in September 2007. Remarkable exponential relationship between soil temperature and soil CO efflux was confirmed each year. However, significant and strong relationship between soil moisture and soil CO efflux was also observed during summer period from July to September. No decreasing trend of stimulatory warming effect on Rh was confirmed over the 10 years of observation. There was a marginally significant relationship between summer precipitation and annual warming effect. This study suggested the relationship between moist environment in Asian monsoon region and the sustained stimulatory soil warming effect on SOC decomposition.