title: Seasonal and Spatial Variations of Bulk Nitrogen Deposition and the Impacts on the Carbon Cycle in the Arid/Semiarid Grassland of Inner Mongolia, China.
abstract: Atmospheric nitrogen (N) deposition is an important component that affects the structure and function of different terrestrial ecosystem worldwide. However, much uncertainty still remains concerning the magnitude of N deposition on grassland ecosystem in China. To study the spatial and temporal patterns of bulk N deposition, the levels of N (NH4+-N and NO3--N) concentration in rainfall were measured at 12 sites across a 1200 km grassland transect in Inner Mongolia, China, and the respective N deposition rates were estimated. The inorganic N deposition rates ranged from 4.53 kg N ha-1 to 12.21 kg N ha-1 with a mean value of 8.07 kg N ha-1 during the entire growing season, decreasing steadily from the eastern to the western regions. Inorganic N deposition occurred mainly in July and August across meadow steppe, typical steppe, and desert steppe, which corresponded to the seasonal distribution of mean annual precipitation. A positive relationship was found between inorganic N deposition and mean annual precipitation (R2 = 0.54 ~ 0.72, P < 0.0001) across the grassland transect. Annual estimation of inorganic N deposition was 0.67 Pg yr-1 in Inner Mongolia, China based on the correlation between N deposition rates and precipitation. N deposition was an important factor controlling aboveground biomass and ecosystem respiration, but has no effect on root biomass and soil respiration. We must clarify that we used the bulk deposition samplers during the entire sampling process and estimated the dissolved NH4+-N and NO3--N deposition rates during the entire growing season. Long-term N deposition monitoring networks should be constructed to study the patterns of N deposition and its potential effect on grassland ecosystem, considering various N species, i.e., gaseous N, particle N, and wet N deposition.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, JiangSu, China.|College of Global Change and Earth System Science, Beijing Normal University, Beijing, China.|Joint Center for Global Change Studies, Beijing, China.
authors.forename: Xianglan
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Huiqiu
authors.initials: H
authors.lastname: Shi
authors.affiliation: University of Chinese Academy of Sciences, Beijing, China.|State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China.
authors.forename: Wenfang
authors.initials: W
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: College of Global Change and Earth System Science, Beijing Normal University, Beijing, China.|Joint Center for Global Change Studies, Beijing, China.|Earth System Science Interdisciplinary Centre, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Xiujun
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing, China.
authors.forename: Longyu
authors.initials: L
authors.lastname: Hou
authors.affiliation: College of Global Change and Earth System Science, Beijing Normal University, Beijing, China.|Joint Center for Global Change Studies, Beijing, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China.
authors.forename: Wenping
authors.initials: W
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing, China.
authors.forename: Linghao
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, JiangSu, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
mesh_terms: D018533:Biomass; D002681:China; D065948:Grassland; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D012621:Seasons
chemical_list: D009584:Nitrogen