Comprehensive geospatial assessment of the soil microbiome’s response to temperature and moisture in interior Alaska, USA

As global temperatures rise, soil fractions of organic matter are being subjected to microbial degradation, particularly in high latitude regions.  Concurrently, permafrost perched below active layer soils is thawing at unprecedented rates, significantly altering landscapes and ecosystem trajectories by changing subsurface conditions and vegetation characteristics. Our aim was to investigate an Alaskan soil microbiome’s response to changes in temperature and water potential because they are well established factors that influence microbial activity and could be predicted using remote sensing data and weather forecasts.  The extent of microbial change in the seasonally thawed active layer remains poorly understood.  To address this, we studied the physical and microbiological properties of two permafrost-affected surface soils in interior Alaska primarily composed of deciduous forests, coniferous forests, and woody wetlands.  We collected soils for laboratory incubation studies where we measured respiration and microbial taxonomy from replicate microcosms experiencing four temperatures and five matric potentials.  Soil respiration rates from the soils varied according to temperature and moisture, with soils exposed to warmer, wetter conditions exhibiting the highest respiration rates (e.g. 0.23 or 0.70 µg C-CO₂ g^-1 dry soil h^-1) and soils exposed to colder, drier conditions exhibiting lower respiration rates (e.g. 0.03 or 0.1 µg C-CO₂ g^-1 dry soil h^-1).   In the field, we measured soil temperature, moisture, and respiration at the sites where the soils were initially collected.  Surface soil temperatures measured at the sites ranged from -25°C in the winter months to +25°C in the summer months.  These values were compared to geospatial estimates of temperature and soil moisture that were used to calculate soil respiration rates.  The estimated respiration values will be compared to field measurements to determine the efficacy of the model.  Additionally, respiration estimates will be calculated under a future climate scenario.  These findings have important implications for developing accurate forecasts of microbial community assemblages during thaw in that location should be considered as a strong influencing factor.