日本地球惑星科学連合2018年大会

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[JJ] ポスター発表

セッション記号 A (大気水圏科学) » A-CG 大気水圏科学複合領域・一般

[A-CG40] 陸域生態系の物質循環

2018年5月24日(木) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:加藤 知道(北海道大学農学研究院)、平野 高司(北海道大学大学院農学研究院)、佐藤 永(海洋研究開発機構 地球表層物質循環研究分野、共同)、平田 竜一(国立環境研究所)

[ACG40-P03] 沖縄島の亜熱帯常緑広葉樹林における土壌呼吸とその構成成分

*速水 眞誉1松本 一穂2谷口 真吾2大橋 瑞江3高嶋 敦史2 (1.琉球大学大学院農学研究科、2.琉球大学農学部、3.兵庫県立大学環境人間学部)

キーワード:土壌呼吸量、根呼吸量、微生物呼吸量、空間変動、亜熱帯常緑広葉樹林

We examined the factors controlling the spatial variation in the soil CO2 efflux (soil respiration) in a subtropical mature evergreen broadleaf forest in northern Okinawa Island. At four locations with different soil respiration values (2.2, 2.5, 10.8, and 15.5 μmol m-2 s-1), we examined the flux components constituting soil respiration (i.e., root respiration and heterotrophic respiration originating from the surface litter and other belowground organic matter) in November 2016. To measure the first two, we sampled roots and the litter layer after measuring soil respiration, and then measured the flux from both in situ using a chamber with an infrared gas analyser. Then, we estimated the heterotrophic respiration from belowground organic matter by subtracting both of these from the total soil respiration. This showed that, at the two locations with the highest soil respiration, the heterotrophic respiration from belowground organic matter was large (7.5 and 10.6 μmol m-2 s-1) and accounted for 68–69% of the total soil respiration. In comparison, it was small at the two locations with low soil respiration. The root biomass and root respiration (0.7–4.3 μmol m-2 s-1) were positively correlated with the soil respiration. Although the biomass of the surface litter was positively correlated with soil respiration, the heterotrophic respiration originating from it was small (0.3–0.7 μmol m-2 s-1). A negative correlation between soil density and soil respiration was found. Based on the results, we postulated that the CO2 flux from live roots, and especially from microbes consuming dead belowground organic matter supplied by litterfall, largely contributes to the spatial variability in the soil CO2 efflux in this forest.