The rise rate of Arctic air temperature is twice as high as that of global warming rate. To date, the response of microbial functional compositions to long-term warming is still obscure in Arctic ecosystem. Therefore, we adopt GeoChip to examine how microbial functional compositions at six soil depth intervals (i.e, 5-15 cm,15-25 cm, 25-35 cm, 35-45 cm, 45-55cm, 55-65 cm) respond to nine years’ warming in Permafrost Heating Research site, Alaska. Experimental warming was achieved by snow fences set up in every winter since 2008, which act as an insulator. ANOVA was used to determine the warming effect on soil environmental variables and relative abundances of microbial functional genes. Microbial functional community response was examined by Permutational multivariate analysis of variance using distance matrices, principal component analysis and non-metric multidimensional. In addition, the linkages between microbial communities and environmental variables were analyzed using canonical correspondence analysis and Mantel tests. The correlations between microbial functional abundances and environmental variables was conducted by linear regression.
Results/Conclusions
Nine-years’ warming significantly increased permafrost thaw depth from 66.08 cm to 98.70 cm but decreased the biomass of Vaccinium Vitis-idaea (VVI). The main effect of soil depth and the interaction of soil depth and warming were significant on overall microbial functional compositions, while warming altered microbial functional compositions only at 15-35 cm and 45-55 cm depths. Most functional genes associated with carbon (C) degradation decreased in relative abundance under warming at 15-25 cm. But warming only decreased the abundances of a few C degradation genes at 25-65 cm. Microbial functional compositions at 15-25 cm was significantly linked to thaw depth and biomass of VVI and Rubus chamaemorus. Microbial functional composition at 45-55 cm was significantly linked to biomass of Oxycoccus Microcarpus. Similarly, the abundances of microbial functional genes associated with C degradation at 15-25 cm depth positively correlated with thaw depth and biomass of VVI (r > 0.70, P < 0.05). However, the correlations were not observed in deeper soils (35-65 cm). We conclude that permafrost ecosystem is sensitive to warming, while thaw depth and plant species may have accounted for the various responses of microbial functional compositions to long-term warming.