title: The effects of warming and nitrogen addition on soil nitrogen cycling in a temperate grassland, northeastern China.
abstract: BACKGROUND
  Both climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood.
  
  
  RESULTS
  A field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland.
  
  
  CONCLUSIONS
  Interactions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem.
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Xiangshan, Beijing, China.
authors.forename: Lin-Na
authors.initials: LN
authors.lastname: Ma
authors.forename: Xiao-Tao
authors.initials: XT
authors.lastname: Lü
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Ji-Xun
authors.initials: JX
authors.lastname: Guo
authors.forename: Nan-Yi
authors.initials: NY
authors.lastname: Zhang
authors.forename: Jian-Qin
authors.initials: JQ
authors.lastname: Yang
authors.forename: Ren-Zhong
authors.initials: RZ
authors.lastname: Wang
mesh_terms: D002681:China; D057231:Climate Change; D017753:Ecosystem; D009584:Nitrogen / Q000737:chemistry*; D058458:Nitrogen Cycle; D012987:Soil / Q000737:chemistry*; D013696:Temperature
chemical_list: D012987:Soil; D009584:Nitrogen
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