Changes of permafrost microbial communities in response to climate warming in Alaska
Permafrost stores about 50% of the total soil organic carbon of the world and is believed to respond actively to global warming. The intense degradation and release of previously stored organic carbon could potentially form positive feedbacks to warming. Microbial activity plays a crucial role in determining C loss in permafrost ecosystems, yet this process is poorly understood. We studied the microbial community changes after being subjected to experimental warming for 4 years in CiPEHR (Carbon in Permafrost Experimental Heating Research) project site, Alaska, by combining comprehensive functional gene analysis using the GeoChip 5.0 and 16s and ITS rRNA amplicon analysis. In addition, statistical analysis such as ANOVA, dissimilarity test and Mantel test were conducted to study the shift of microbial community and major environmental factors.
Genes involved in biogeochemical cycling of C and N were enriched under warming, e.g. labile carbon degradation, C fixation, methane production, N fixation and denitrification. In particular, the significant enrichment of genes involved in Methanogenesis suggested that methane release could be potentially increased under warming. Also, nitrous oxide could be induced due to the induced gene coding enzyme norB which reduces NO to N2O. 16s rRNA analysis showed the composition of microbial community changed in response to warming. Verrucomicrobia, Firmicutes and Chlorobi were increased while Actinobacteria and Armatimonadetes were decreased, which indicate that microbial community was shifted under warming. In addition, both Mantel test and CCA(Canonical Correspondence Analysis) showed these changes in function and diversity could be largely explained by three environmental factors, plant growth, temperature and moisture.