Quantifying the spatial heterogeneity of soil organic matter and minerals at the microscale based on NanoSIMS meta-analysis

High-resolution imaging approaches revealed heterogeneous soil microstructure with latent spatial patterns that are interrelated with biogeochemical matter cycles in soils. Previous reports of the patchy distribution of soil organic matter (OM) at the microscale demand for extensive of the spatial coverage and arrangement of OM across mineral surfaces in soils. Here, we present a meta-analysis based on nanoscale secondary ion mass spectrometry (NanoSIMS) measurements and a machine-learning segmentation providing insights into diverse soil samples. We identified the coverage of OM across mineral surfaces to be correlated with the bulk soil OM content, showing the expanding but limited arrangement of OM. We employed a lacunarity approach to evaluate the spatial heterogeneity based on the heterogeneous distribution of C and N. This analysis reveals the heterogenous patterns across OM size and its C and N composition within OM, indicating different compositional and structural properties with the OM.  In our contribution, we provide novel pathways to evaluate the heterogeneous arrangement of OM in soils across mineral surfaces at the microscale.