Functional and structural responses of bacterial and methanogen communities to 3-year warming incubation in different depths of peat mire

Global warming is expected to have greater impacts on northern peatlands in coming decade than most other ecosystems. Bacterial and methanogen communities in peatlands play a role in greenhouse gas emissions, and provide a feedback to global climate change. We investigated 3-degree warming effects on gas emissions (CO2 and CH4) and bacterial and methanogen communities in different depths of peat mire for 3 growing seasons. Warming doubled CO2 fluxes from the warming treatments compared to that from the control (P=0.08). Although CH4 fluxes were higher in the warming treatment, it was not a significant increase. Warming caused a shift in the composition of bacterial communities in the surface (1-3 cm, P<0.01) and middle layers (9-11 cm, P < 0.01), but not in the deep layer (17-19 cm). There were few changes in the diversity indices and quantity of bacterial communities due to the warming treatments. Warming significantly decreased the richness. Shannon diversity index, and quantity of methanogens. However, the composition was hardly related to temperature. The ratios of methanogens to bacteria in terms of gene copy numbers significantly decreased by a factor of 2-6 due to elevated temperature. The composition and diversity of bacteria and methanogens, respectively, were significantly related to soil depth. Temperature and soil depth interacted significantly on the bacterial diversity (P=0.01). The results suggest that warming is likely to influence the function and structure of microbial communities in peat lands. However, warming effects would be different with the type of microbial community and soil depth. Warming could favor bacterial communities over methanogens, which may induce changes in balance between CO2 and CH4 emissions from peatlands. (C) 2012 Elsevier B.V. All rights reserved.