title: Soil bacterial communities shaped by geochemical factors and land use in a less-explored area, Tibetan Plateau.
abstract: BACKGROUND
  As the largest low-latitude permafrost region, the Tibetan Plateau (TP) is an important part of the earth's terrestrial ecosystem and one of the most vulnerable areas to climate change and human activities. However, to the best of our knowledge, the bacterial communities in TP soils and their roles in biogeochemical cycles remain limited.
  
  
  RESULTS
  In this study, we report the bacterial community structure and function as well as their correlation with environmental factors in TP major ecosystems (farmland, alpine meadow and oligosaline lake) by using metagenomic approaches. Compared with other soil samples in various environments, TP soils share a core set of microorganisms with a distinct abundance and composition. Among TP soil samples, the taxonomic and functional composition of bacterial communities among the upper (3-5 cm) and lower (18-20 cm) soils of farmland sites were highly similar, whereas the dissimilarities within alpine meadow samples were significantly greater than among farmland samples. A similar pattern was observed in elements cycles and pathways associated with adaption to environment and land use types. Canonical correlation analysis revealed that the bacterial communities in most of farmland and alpine meadow soil samples were also significantly correlated with geogenic variables. Specifically, the root-nodule bacteria are negatively correlated with the soil moisture and pH, while Thiobacillus associated with sulfur cycles show potential responses to low temperature and intense UV radiation.
  
  
  CONCLUSIONS
  These findings indicate that the bacterial community structure and functions in TP soils were influenced by both human activities and soil environmental properties, and that the bacterial communities appeared to be more homogenized in the farmland soils compared with pristine alpine meadows.
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Guan
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.forename: Ximing
authors.initials: X
authors.lastname: Luo
authors.affiliation: Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, China. feiliu@cugb.edu.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Fangqing
authors.initials: F
authors.lastname: Zhao
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D004777:Environment; D055593:Geological Phenomena; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013696:Temperature; D018609:Tibet
chemical_list: D012987:Soil