Long-term warming effect on heterotrophic respiration in a warm-temperate evergreen broad -leaved forest in western Japan

西日本の暖温帯常緑広葉樹林における温暖化の土壌微生物呼吸への長期的影響

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

Soil respiration is the second largest carbon flux in terrestrial ecosystem, and it consists of soil organic carbon decomposition by microbiota (heterotrophic respiration, Rh) and plant root respiration. Rh corresponds to more than half of soil respiration and 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 warming effect on Rh, we set multi-channel automated chamber and artificial warming system in a warm-temperate evergreen broad-leaved forest in Higashi Hiroshima, western Japan. Seasonal changes of CO effluxes in control (Rh) and warmed (Rhw) treatment were largely dependent on soil temperature. However, the influence of soil moisture was also strong during summer period from July to September due to low precipitation. Annual Q values were ranged from 2.19 to 3.64 in Rh and from 2.11 to 3.57 in Rhw. Stimulatory warming effect on Rh was continuously confirmed over the 10 years of observation. The annual increased ratio of Rh due to soil warming by 1C (annual warming effect) ranged from 4.2 to 13.5%. There was a marginally significant relationship between summer precipitation and annual warming effect. The result suggested that the annual warming effect was controlled by summer precipitation and resulting soil moisture level in this research site.