[A-CG30] 陸域生態系における水・炭素・窒素などの循環に関する研究

[ACG30-03] 九州暖温帯常緑広葉樹林における土壌呼吸に対する長期的な温暖化効果

*寺本 宗正¹、梁 乃申¹、高木 正博²、曾 継業¹ (1.国立環境研究所地球環境研究センター、2.宮崎大学 農学部)

キーワード：土壌呼吸, 温暖化, チャンバー, 森林土壌

Soil respiration is composed of heterotrophic respiration and plant root respiration, and is the second largest carbon flux in the terrestrial ecosystem. As the heterotrophic respiration increases exponentially with soil temperature, its positive feedback to the global warming has become a concern.
In the middle of December 2008, a multi-channel automated chamber measurement system was installed at the Tano forest science station of Miyazaki University, which is a warm-temperate broad-leaved forest site in Kyusyu. We prepared 10 trenched plots with 5 of them artificially warmed by +2.5℃ by infrared heaters 1.6 m above the surface for long-term measurement of warming effect on soil respiration.
The average value of soil respiration in control and warmed plots were, respectively, 3.45 μmol CO₂ m^-2 s^-1 and 3.53 μmol CO₂ m^-2 s^-1 in 2009, 3.81 μmol CO₂ m^-2 s^-1 and 4.07 μmol CO₂ m^-2 s^-1 in 2010, 3.31 μmol CO₂ m^-2 s^-1 and 3.81 μmol CO₂ m^-2 s^-1 in 2011, 3.02 μmol CO₂ m^-2 s^-1 and 3.79 μmol CO₂ m^-2 s^-1 in 2012, 3.08 μmol CO₂ m^-2 s^-1 and 3.33 μmol CO₂ m^-2 s^-1 in 2013. The annual warming effect increased soil respiration by 5.4% in 2009, 9.9% in 2010, 18.4% in 2011, 29.5% in 2012, and 11.5% in 2013. The warming effect showed an increasing trend until 2012, but decreased in 2013 due to fewer amount of rainfall in summertime, which caused a much lower moisture in soil.