Effects of climate change on microbial taxonomy and metabolic processes in Alaskan permafrost-affected soils

Permafrost is thawing at unprecedented rates, significantly altering landscapes and ecosystem trajectories by changing subsurface conditions and vegetation characteristics. The combination of in situ and laboratory analysis is important to understand microbial heterogeneity and to simulate the effects of thaw.  Dormant microbes become active as temperatures rise and permafrost soils warm and thaw, suggesting that sub-surface ecosystem processes will be altered. The extent of microbial change throughout seasons and thaw periods remain poorly understood.  We collected permafrost-affected soils at two Alaskan sites to determine the effects of sample location and warming on the permafrost microbiome.  In situ analysis of northern Alaskan soils revealed that surface communities were highly variable throughout the growing season.  In two laboratory thaw studies, we assessed permafrost microbiome taxonomy and metabolic function during thaw.  Under frozen conditions, microbial respiration rates from different PT locations were similar, ranging from 2 to 12 mg C–CO₂ per kg soil per day and permafrost microorganisms were heterogeneously distributed in space.  Following thaw, metabolomes from different locations were highly similar.  However, the trajectory of dominant taxa and potential function in a given PT sample was more strongly influenced by sample location than by incubation temperature. This indicates a differential response of permafrost microbes based on their origin. 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.