Data from: Deciphering soil fertility and microbial community structures into ecosystem functions in boreal forest floors

Soil microorganisms drive ecosystem processes including carbon cycling. Their functions are simultaneously influenced by microbial community and the environment, but resolving these two sets remains a challenge. Therefore, we conducted two transplantation experiments, i.e., plant-soil transplantation and plant transplantation, along natural fertility gradients in three boreal forests. One-year plant-soil transplantation altered physicochemical variables (e.g., pH and C:N ratio), significantly changed microbial metabolic rates and biomass turnover, but did not shift community structure, indicating that fertility drove these short-term physiological changes. Along the natural soil fertility gradients, there were pronounced differences in soil physicochemical variables (e.g., N availability, phosphate, pH, and C:N ratio), and profound shifts in microbial community structure and the balance between functional groups, however, soil microbial metabolic rates and biomass turnover time showed no significant difference. This suggested that restructuring the microbial community could compensate for new environmental conditions to maintain microbial metabolic rates and biomass turnover times. In contrast, microbial carbon use efficiency (CUE) was unaffected by the alignment between microbial community structure and the environmental conditions, suggesting that CUE was primarily determined by soil environmental variables while the microbial community structure played a minor role. Short-term plant transplantation rarely affected soil physicochemical or microbial variables, suggesting the changes in the boreal forest understory are insufficient to detectably affect microbial functions within a year. Our results show that soil environmental variables and microbial community structure can both affect the soil functions underpinned by microbial physiological rates, while the partitioning of C between respiration and growth (the microbial CUE) is dominantly controlled by environmental conditions.