On Upscaling of Soil Microbial Processes and Biogeochemical Fluxes From Aggregates to Landscapes

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AbstractSoil microbial communities respond to spatial and temporal variations in environmental conditions (e.g., saturation and ambient temperatures) as reflected in the dynamics of microbially produced greenhouse gas (GHG) fluxes (primarily CO2, N2O, and CH4) emitted from soil surfaces. Despite considerable progress in resolving key soil microbial processes, their quantification remains largely empirical with limited predictability. We report a mechanistic and analytical modeling framework for integrating local environmental effects on GHG‐producing microbial processes primarily in soil aggregates (or other hot spots) and the upscaling of these to regional GHG fluxes. The mechanistic model enables systematic evaluation of how soil structural features (e.g., aggregation and layers), spatial variability, and dynamic ambient conditions (e.g., temperature and hydration) affect soil microbial functioning. The upscaling of microbial processes from aggregates of different sizes to soil profiles and landscapes implements mechanistically derived microbial response functions with spatial information on soil type, land cover, and resource distribution. The modeling framework was evaluated using reported field data for seasonal N2O emissions from subarctic regions resulting in reasonable agreement. The proposed analytical framework offers a practical compromise balancing a simplified representation of dynamic microbial processes that respond to local conditions with an upscalable representation of soil GHG fluxes over landscapes under changing environmental conditions.