Stable carbon and nitrogen isotopes in water-extractable organic matter from air-dried soils to elucidate microbial utilization of substrate organic matter in a Japanese temperate forest

温帯林土壌の微生物による基質有機物利用動態の解明に向けた風乾土壌の水抽出有機物の安定同位体比分析

永野 博彦*; 安藤 麻里子  ; 田中 草太*; 小嵐 淳   

Nagano, Hirohiko*; Atarashi-Andoh, Mariko; Tanaka, Sota*; Koarashi, Jun

Microbial decomposition of soil organic matter (OM) is crucial in terrestrial carbon cycle, whereas the soil analytical approach elucidating the decomposition is still halfway to the achievements. Forty air-dried soil samples were applied to water extraction and OM analysis. The C and N contents and natural abundances of C and N exhibited positive correlations between the bulk soil and water-extractable fraction. However, the C/N ratio in water-extractable fraction showed a value around 10 regardless of that in bulk soil, indicating that water-extractable OM is likely derived from microbial cells. C and N enrichments in water-extractable fraction were, respectively, negatively and positively correlated with contents of organo-mineral complexes and short-range order minerals, which control the stabilization of OM in Japanese forest soils. Those enrichments likely reflect the microbial utilization of soil C and N under different substrate availability.