科研之友
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摘要
While microbial-mineral-organic matter interactions are key features controlling the fates of low molecular-weight compounds in soils, direct investigations of how they control their fine-scale spatial distribution are scant. Here, we addressed how microbial transformations affect the retention of C-13/N-15-labeled glycine in a forest topsoil 8 h after application. We assessed the contribution of soil microorganisms to glycine-derived C-13 and N-15 retention using gamma-irradiated and non-irradiated soils. We tracked down the glycine-derived C-13 and N-15 at the surface of particles randomly isolated from soil density fractions using nano-scale secondary ions mass spectrometry (NanoSIMS) imaging. Eight hours after addition, 7 % of the glycine-derived C-13 and N-15 initially applied was recovered among soil density fractions, mainly via the activity of soil microorganisms (> 85 % of total retention). Glycine-derived C-13 and N-15 distribution among density fractions was correlated with that of soil organic matter (SOM) determined by NanoSIMS (R a parts per thousand yen 0.85), suggesting that the spatial patterns of the mineral-attached SOM controls the spatial distribution of the glycine-derived C-13 and N-15. NanoSIMS images showed largely decoupled glycine-derived C-13 and N-15 spots preferentially attached to aggregated particles. We speculate that the glycine-derived C-13 was principally found within or in the vicinity of microbial cells, whereas the glycine-derived N-15 was mostly found as NH4 (+) and/or exoenzymes spread across soil surfaces. The C:N ratios determined by NanoSIMS suggest that local chemical properties of mineral-attached SOM drive glycine-derived N-15 attachment, with the preferential attachment to mineral-attached SOM rich in N (C:N ratios mostly < 16). Few exceptions were found in presence of Al and Fe (hydr)oxides (> 2.65 g cm(-3)).
- 出版日期2015-9
