title: Stoichiometry and large-scale patterns of leaf carbon and nitrogen in the grassland biomes of China.
abstract: Nitrogen (N) and carbon-nitrogen (C:N) ratio are key foliar traits with great ecological importance, but their patterns across biomes have only recently been explored. We conducted a systematic census of foliar C, N and C:N ratio for 213 species, from 41 families over 199 research sites across the grassland biomes of China following the same protocol, to explore how different environmental conditions and species composition affect leaf N and C:N stoichiometry. Leaf C:N stoichiometry is stable in three distinct climatic regions in Inner Mongolia, the Tibetan Plateau, and Xinjiang Autonomous Region, despite considerable variations among co-existing species and among different vegetation types. Our results also show that life form and genus identity explain more than 70% of total variations of foliar N and C:N ratio, while mean growing season temperature and growing season precipitation explained only less than 3%. This suggests that, at the biome scale, temperature affects leaf N mainly through a change in plant species composition rather than via temperature itself. When our data were pooled with a global dataset, the previously observed positive correlation between leaf N and mean annual temperature (MAT) at very low MATs, disappeared. Thus, our data do not support the previously proposed biogeochemical hypothesis that low temperature limitations on mineralization of organic matter and N availability in soils lead to low leaf N in cold environments.
authors.affiliation: Department of Ecology, College of Environmental Sciences and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, 5 Yiheyuan Rd., 100871 Beijing, China. jshe@pku.edu.cn
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: He
authors.forename: Jingyun
authors.initials: J
authors.lastname: Fang
authors.forename: Zhiheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Dali
authors.initials: D
authors.lastname: Guo
authors.forename: Dan F B
authors.initials: DF
authors.lastname: Flynn
authors.forename: Zhi
authors.initials: Z
authors.lastname: Geng
mesh_terms: D000704:Analysis of Variance; D002244:Carbon / Q000032:analysis*; D002681:China; D017753:Ecosystem; D005843:Geography; D009584:Nitrogen / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry*; D006109:Poaceae / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature
chemical_list: D002244:Carbon; D009584:Nitrogen