B103-01
Linking soil organic matter stabilization with mineral surface binding, aggregation, and microbial metabolism

Tuesday, 15 December 2020: 16:00
Virtual
Rota Wagai, Nat. Inst. Agro-Environ Sci, Tsukuba-City, Ibarag, Japan, Masako Kajiura, National Agriculture and Food Research Organization, Institute for Agro-Environmental Sciences, Tsukuba, Japan, Maki Asano, University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan and Yudzuru Inoue, Nagasaki Institute of Applied Science, Nagasaki, Japan
Recorded Presentation
Abstract:
  • Mineral protection of soil (and sediment) organic matter (SOM) is increasingly recognized. Mineral protection via OM sorption on mineral surfaces, complexation, and coprecipitation with reactive metals (Fe, Al) possibly together with metalloids (Si), and physical occlusion via aggregation has been suggested based on both experimental and field-based evidence. Yet the relative importance or localization of these processes in field soils remain poorly understood.
  • Soil contains young, labile OM derived from primary production as well as more stable, often more microbially-processed and mineral-protected OM. They are, in fact, present as a continuum in most soils. Thus, a more mechanistic understanding of the microbially-driven progressive transformation of plant-derived OM to stable OC is critical to predict the response of these OC pools to climate change and anthropogenic disturbances or to enhance SOM storage potential for C sequestration and agricultural sustainability.
  • This transformation has been effectively studied by density fractionation approach that has shown a coherent pattern that soil particles (including aggregated particles) of higher density hold older OM which is more enriched in C-13 and N-15 (due most likely to microbial recycling) across a wide range of soils.
  • Using 23 soil samples from 5 climate zones and 5 soil orders (Andisols, Spodosols, Inceptisols, Mollisols, Ultisols), we recently showed that major portions of SOM and reactive metal phases were present as stable microaggregates in meso-density fractions (1.8-2.4 g/cc) and suggested the significant role of organo-metal rich nanocomposites as a key binding agent (organo-metallic glue hypothesis) based on OM-metal stoichiometric relationship across density fractions.
  • In this presentation, we further discuss how the observed co-localization of reactive metals and OM in meso-density range is linked with microbial metabolism (C-13, N-15 enrichment) and the protective roles of mineral surface and reactive metal phases for OM stabilization.
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