Stable C and N isotope abundances in water-extractable organic matter from air-dried soils as potential indices of microbially utilized organic matter

作者：Hirohiko Nagano, Mariko Atarashi-Andoh, Sota Tanaka, Takumi Yomogida, Naofumi Kozai, Jun Koarashi · 发表于：Frontiers in Forests and Global Change · 年份：2023 · DOI：10.3389/ffgc.2023.1228053 · 被引用次数：11 · 研究领域：Soil Carbon and Nitrogen Dynamics、Soil and Water Nutrient Dynamics、Peatlands and Wetlands Ecology

Stable carbon (C) and nitrogen (N) isotopes ( 13 C and 15 N) in water-extractable organic matter (WEOM) derived from air-dried soils may be applicable to elucidate the microbial decomposition of soil organic matter (SOM), which is crucial in terrestrial C cycles. A total of 40 soil samples were collected from a depth of 0–6 cm from a temperate broadleaved forest in Japan with vegetation succession from grassland approximately 150 years ago. Those soil samples were air-dried before the water extraction process and organic matter analysis. The C and N concentrations of WEOM were <3.6% of those of the bulk soil and were positively correlated with those of the bulk soil at a p -value of < 0.01. A positive correlation between the two fractions (i.e., WEOM and bulk soils) was also found for natural 13 C and 15 N abundances (δ 13 C and δ 15 N; p < 0.01). However, the C/N ratio of WEOM was slightly correlated with that of bulk soils, exhibiting a narrow range of values of ~10. Thus, those features of the WEOM were similar to the well-known features of microbial biomass. The δ 13 C and δ 15 N enrichments in WEOM relative to bulk soil, the difference in stable isotope abundances between bulk SOM and WEOM were negatively and positively correlated, respectively, with the concentrations of organo-mineral complexes and short-range order minerals (non-crystalline oxyhydroxides of aluminum and iron, allophane, imogolite, and allophane-like constituents), which play signi...