title: [Impact of land-use type changes on soil nitrification and ammonia-oxidizing bacterial community composition].
abstract: A comparative study was conducted to determine nitrification potentials and ammonia-oxidizing bacterial (AOB) community composition in 0-20 cm soil depth in adjacent native forest,natural grassland, and cropland soils on the Tibetan Plateau, by incubation experiment and by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA, respectively. Cropland has the highest nitrification potential and nitrate concentration among the three land-use types (LUT), approximately 9 folds and more than 11 folds than that of the forests and grasslands, respectively. NO3(-) -N accounted for 70%-90% of inorganic N in cropland soil, while NH4(+) -N was the main form of inorganic N in forest and grassland soils. Nitrification potentials and nitrate concentrations showed no significant difference between native forest and grassland soils. The native forest showed the lowest nitrification potentials and the lowest AOB diversity and community composition among the three LUT. Conversions from natural grasslands to croplands remarkably decreased the AOB diversity and composition, but croplands remain high similarity in AOB community composition compared with grasslands. The minimal and the lowest diversity of AOB in native forests directly resulted to the lowest nitrification potentials compared to natural grasslands and croplands. From the fact of the highest nitrification potentials and nitrate concentrations in croplands indicated that there were the most substantial AOB with higher activity and priority. The results provide evidence that changes of land-use type can affect both soil nitrogen internal cycling process, the diversity, community and activity of AOB, which further affect soil environment quality and the long-term sustainability of ecosystems.
authors.affiliation: Key Laboratory of Agricultural Water Resources, Center for Agricultural Research Resources, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021, China. yangllin@sjziam.ac.cn
authors.forename: Li-Lin
authors.initials: LL
authors.lastname: Yang
authors.forename: Ren-Zhao
authors.initials: RZ
authors.lastname: Mao
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Liu
authors.forename: Xiao-Jing
authors.initials: XJ
authors.lastname: Liu
mesh_terms: D000383:Agriculture; D000531:Altitude; D001419:Bacteria / Q000145:classification / Q000254:growth & development / Q000378:metabolism*; D058465:Nitrification; D009576:Nitrobacter / Q000254:growth & development / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D006109:Poaceae / Q000254:growth & development; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D018609:Tibet; D014197:Trees / Q000254:growth & development
chemical_list: D000644:Quaternary Ammonium Compounds; D012987:Soil; D009584:Nitrogen