[A-CG39] 陸域生態系の物質循環

[ACG39-P01] 苗場山ブナ林における微生物呼吸に対する長期的な温暖化の影響

*寺本 宗正¹、梁 乃申¹、楢本 正明²、曾 継業¹、趙 昕¹、冨松 元¹ (1.国立環境研究所地球環境研究センター、2.静岡大学農学部)

キーワード：土壌有機炭素、地球温暖化、微生物呼吸、チャンバー、アジアモンスーン

Soil respiration is the second largest carbon flux in terrestrial ecosystems and the global soil respiration is estimated to be 98 GtC yr^-1. Soil respiration consists of root respiration and heterotrophic respiration (R_h), and R_h contributes more than half of the soil respiration. It is commonly observed that R_h exponentially increases with temperature. Therefore, a small increase of temperature can result in a remarkable enhancement of R_h, indicating that it is an important positive feedback factor to accelerate global warming under a warmer environment. However, the long-term warming effect on R_h is not well understood especially in the humid Asian monsoon region.

To examine the long-term response of R_h to global warming in Asian monsoon forests, we set a multi-channel automated chamber measurement system in a beech forest on Mount Naeba in July 2007. We prepared 10 trenched chambers (90 cm × 90 cm × 50 cm) to continuously measure R_h. Half of those trenched chambers were artificially warmed by infrared heaters 1.6 m above the soil surface (+2.5ºC), and the influence of soil warming on R_h was examined by comparing control plots and warming plots. Measurements were conducted mainly during growing season from June to October.

Even though there was a large inter-annual variation, enhancement of R_h by soil warming was confirmed in all 8 years measurements. Soil temperature was the primary factor for the seasonal variation of R_h. The influence of soil moisture on seasonal variation of R_h was relatively small.