Abstract: Peat bogs are the most effective terrestrial ecosystems for long-term carbon storage. Hydrologic characteristics and micro-topography may affect carbon storage in peatlands by regulating the composition and function of microbial communities. In the site located in the peat bog of Jinchuan in Changbai Mountain, we collected soil samples in hummock and hollow of Carex schmidtii from eight different levels of the depth to water table (-10, -1, 0, 4, 10, 13, 14 and 18 cm), to explore the effects of depth to water table and microtopography on soil microbial biomass carbon and nitrogen, enzyme activity, and methane functional genes. Results showed that the effects of the depth to water table on the content of microbial biomass carbon and nitrogen differed across different soil layers, with a significant positive correlation with microbial biomass carbon and nitrogen in the 30-45 cm soil layer of hummock and the 0-15 cm soil layer of hollow. The activities of enzymes (β-1,4-glucosidase and β-1,4-Nacetylglucosamine glycosidase) related with soil carbon and nitrogen cycling were significantly positively correlated with the depth to water table and regulated by soil layer, while the phosphatase activities were not correlated with the depth to water table. In addition, the depth to water table had a significant negative correlation with the abundance of methanogenesis bacteria (the copy number of mcrA functional gene per gram dry soil), and a significant positive correlation with the abundance of methaneoxidizing bacteria (the copy number of pmoA functional gene per gram dry soil), with a stronger effect of the depth to water table on the abundance of methanogenesis bacteria. The microtopography significantly affected microbial biomass carbon and nitrogen, with higher microbial biomass carbon and nitrogen in hummock than in hollow at the same 15-30 cm soil layer and higher microbial biomass carbon in 15-30 cm soil layer of hollow than in 0-15 cm soil layer of hummock. Themicro topography significantly affected the abundance of methaneoxidizing bacteria, which was higher in hummock than in hollow in the same 15-30 cm soil layer. Our results indicated that the spatial heterogeneity of peatlands would affect microbial activity, which should be fully considered in scaling up the results from local to large scale.

Key words: microbial biomass carbon and nitrogen, enzyme activity, mcrA gene, pmoA gene.