Soil Microbial Activities in Beech Forests Under Natural Incubation Conditions as Affected by Global Warming

Microbial activity in soil is known to be controlled by various factors. However, the operating mechanisms have not yet been clearly identified, particularly under climate change conditions, although they are crucial for understanding carbon dynamics in terrestrial ecosystems. In this study, a natural incubation experiment was carried out using intact soil cores transferred from high altitude（1 500 m） to low（900 m） altitude to mimic climate change scenarios in a typical cold-temperate mountainous area in Japan. Soil microbial activities, indicated by substrate-induced respiration（SIR） and metabolic quotient（q CO2）, together with soil physicalchemical properties（abiotic factors） and soil functional enzyme and microbial properties（biotic factors）, were investigated throughout the growing season in 2013. Results of principal component analysis（PCA） indicated that soil microbial biomass carbon（MBC） andβ-glucosidase activity were the most important factors characterizing the responses of soil microbes to global warming. Although there was a statistical difference of 2.82 ℃ between the two altitudes, such variations in soil physical-chemical properties did not show any remarkable effect on soil microbial activities, suggesting that they might indirectly impact carbon dynamics through biotic factors such as soil functional enzymes. It was also found that the biotic factors mainly controlled soil microbial activities at elevated temperature,which might trigger the inner soil dynamics to respond to the changing environment. Future studies should hence take more biotic variables into account for accurately projecting the responses of soil metabolic activities to climate change.