Pattern of soil methanotrophs on the natural vertical zones of the North Tianshan Mountain

Methane is one of the most important greenhouse gases and plays an essential role in atmospheric chemistry. Knowledge about methanotrophs and their diversity is important to understand the microbial mediation of the greenhouse gas CH4 under climate change. The methanotrophs is one of main functional microbial groups in soil mediating methane cycles of terrestrial ecosystem. The purpose of this study was to explore spatial distribution pattern of methanotrophs diversity and the major factors affecting soil methanotrophs diversity along an elevation gradient on vertical natural belt of the North Tianshan Mountains, soil samples were collected at six sites in 2010, which were desert grassland belt (H1), Mountain grassland belt (H2), Mountain forest belt (H3), sub-alpine cushion belt (H4), alpine cushion belt (H5), alpine tundra vegetation (H6). Methanotrophs diversity in six sites from the North Tianshan Mountain were assessed with terminal restriction fragment length polymorphism (T-RFLP).The carbon–nitrogen ratio was significant difference under different vertical natural belt, ranged from 10.34 to 20.10, soil organic carbon were lowest in alpine tundra vegetation and highest in Mountain forest belt, those numbers of belts ranging from H1 to H3 were increased, with increasing elevation, then H3 to H6 were decreased. The total number of Terminal Restriction Fragments (T-RFs) derived from all those soil samples was 233, indicating high genetic diversity of methanotrophs on vertical natural belt of the North Tianshan Mountains. Microbial communities of T-RFs 55 bp, 242 bp, 376 bp represented the dominant species in sampling sites. However, some of the T-RFs were more sensitive to environment, such as 79 bp, 176 bp and 250 bp. Methanotrophs diversity index and T-RFs numbers were lowest in mountain forest belt and highest in subalpine cushion belt. Along the elevation gradient, the trendency of those numbers are as follows, H1>H2>H3

H5>H6. Cluster analysis revealed that the samples could be separated into two groups, H4, H5 and H6 clustered into one group, while H2 and H3 clustered into other group.The community shifts were further investigated by Principle component analysis (PCA). The first PCA axis, which is related to the main compositional variation, separated the communities of the different sites. The main variation was mainly caused by changes in the relative abundance of the 58 bp, 87 bp, 137 bp, 243 bp and 248 bp T-RFs.Based on canonical correspondence analysis (CCA), Shannon index(H) of methanotrophs was positively correlated with soil pH and C/N ratio and negatively correlated with elevation, content of total nitrogen and total phosphorus; and Simpson index (D) and Evenness (E) were positively correlated with soils’ C/N ratio, soil surface temperature, pH and organic carbon, and negatively with elevation, total nitrogen and total phosphorus; indicating that plant communities and soil nutrients influence the soil microbial structure.Our research showed that soil methanotrophs was high genetic diversity along the elevation gradient on vertical natural belt in the North Tianshan Mountain. Soil microorganisms were positively correlated with vegetation, soils pH, C/N ratio, and soil moisture, total nitrogen, these parameters might be the main factors controlling soil methanotrophs diversity.