title: Effects of warming and grazing on soil N availability, species composition, and ANPP in an alpine meadow.
abstract: Uncertainty about the effects of warming and grazing on soil nitrogen (N) availability, species composition, and aboveground net primary production (ANPP) limits our ability to predict how global carbon sequestration will vary under future warming with grazing in alpine regions. Through a controlled asymmetrical warming (1.2/1.7 degrees C during daytime/nighttime) with a grazing experiment from 2006 to 2010 in an alpine meadow, we found that warming alone and moderate grazing did not significantly affect soil net N mineralization. Although plant species richness significantly decreased by 10% due to warming after 2008, we caution that this may be due to the transient occurrence or disappearance of some rare plant species in all treatments. Warming significantly increased graminoid cover, except in 2009, and legume cover after 2008, but reduced non-legume forb cover in the community. Grazing significantly decreased cover of graminoids and legumes before 2009 but increased forb cover in 2010. Warming significantly increased ANPP regardless of grazing, whereas grazing reduced the response of ANPP to warming. N addition did not affect ANPP in both warming and grazing treatments. Our findings suggest that soil N availability does not determine ANPP under simulated warming and that heavy grazing rather than warming causes degradation of the alpine meadows.
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008 China. wangship2008@yahoo.cn
authors.forename: Shiping
authors.initials: S
authors.lastname: Wang
authors.forename: Jichuang
authors.initials: J
authors.lastname: Duan
authors.forename: Guangping
authors.initials: G
authors.lastname: Xu
authors.forename: Yanfen
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Zhang
authors.forename: Yichao
authors.initials: Y
authors.lastname: Rui
authors.forename: Caiyun
authors.initials: C
authors.lastname: Luo
authors.forename: Burenbayin
authors.initials: B
authors.lastname: Xu
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Zhu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Chang
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Cui
authors.forename: Haishan
authors.initials: H
authors.lastname: Niu
authors.forename: Xinquan
authors.initials: X
authors.lastname: Zhao
authors.forename: Wenying
authors.initials: W
authors.lastname: Wang
mesh_terms: D000818:Animals; D018533:Biomass; D057231:Climate Change; D017753:Ecosystem; D005308:Fertilizers; D009584:Nitrogen / Q000737:chemistry* / Q000378:metabolism; D063245:Plant Development; D010944:Plants / Q000145:classification* / Q000235:genetics; D012987:Soil / Q000737:chemistry*; D013045:Species Specificity; D013997:Time Factors
chemical_list: D005308:Fertilizers; D012987:Soil; D009584:Nitrogen