Soil:AK_tundra_incubation Raw sequence reads

The susceptibility of soil organic carbon (SOC) in tundra to microbial decomposition under warmer climate scenarios potentially threatens a massive positive feedback to climate change, but the underlying mechanisms of stable SOC decomposition are ambiguous. Alaskan tundra soils from three depths (a fibric O horizon with litter and course roots, an O horizon with decomposing litter and roots, and a mineral-organic mix, laying just above the permafrost) were incubated. Resulting respiration data were assimilated into a 3-pool model to derive decomposition kinetic parameters for fast, slow, and passive SOC pools. Bacterial, archaeal, and fungal taxa and microbial functional genes were profiled throughout the 3-year incubation. Correlation analyses and a Random Forest approach revealed associations between estimated decomposition parameters and microbial community profiles, taxa, and traits. There were more associations between the microbial community data and slow and passive SOC parameters than fast SOC parameters. Also, microbial community profiles were better predictors of SOC parameters in deeper soils, which had higher mineral contents and relatively greater quantities of old SOC than surface soils. Overall, our analyses revealed the functional potential of microbial communities to decompose tundra SOC through a suite of specialized genes and taxa. These results portray divergent strategies by which microbial communities access SOC pools across varying depths, lending mechanistic insight into the vulnerability of what is considered stable SOC in tundra regions.