title: Warming decreased and grazing increased plant uptake of amino acids in an alpine meadow.
abstract: Organic nitrogen (N) uptake by plants has been recognized as a significant component of terrestrial N cycle. Several studies indicated that plants have the ability to switch their preference between inorganic and organic forms of N in diverse environments; however, research on plant community response in organic nitrogen uptake to warming and grazing is scarce. Here, we demonstrated that organic N uptake by an alpine plant community decreased under warming with (13)C-(15)N-enriched glycine addition method. After 6 years of treatment, warming decreased plant organic N uptake by 37% as compared to control treatment. Under the condition of grazing, warming reduced plant organic N uptake by 44%. Grazing alone significantly increased organic N absorption by 15%, whereas under warming condition grazing did not affect organic N uptake by the Kobresia humilis community on Tibetan Plateau. Besides, soil NO 3-N content explained more than 70% of the variability observed in glycine uptake, and C:N ratio in soil dissolved organic matter remarkably increased under warming treatment. These results suggested warming promoted soil microbial activity and dissolved organic N mineralization. Grazing stimulated organic N uptake by plants, which counteracted the effect of warming.
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Ma
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota Northwest Institute of Plateau Biology Chinese Academy of Sciences Xining 810008 China.
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Resource and Environment University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Rongxiao
authors.initials: R
authors.lastname: Che
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China.
authors.forename: Hanke
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Resource and Environment University of Chinese Academy of Sciences Beijing 100049 China ; Huairou Ecological and Environmental Observatory Chinese Academy of Sciences Beijing 101408 China.
authors.forename: Haishan
authors.initials: H
authors.lastname: Niu
authors.affiliation: Laboratory of Alpine Ecology and Biodiversity Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100101 China ; CAS Center for Excellence in Tibetan Plateau Earth Science Beijing 100101 China.
authors.forename: Shiping
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Life Sciences University of Chinese Academy of Sciences Beijing 100049 China ; Huairou Ecological and Environmental Observatory Chinese Academy of Sciences Beijing 101408 China.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Cui
keywords: 13C–15N‐glycine; Qinghai–Tibetan Plateau; amino acid uptake; grazing; plant community; warming