title: [Plant N status in the alpine grassland of the Qinghai-Tibet Plateau: base on the N: P stoichiometry].
abstract: Plants from different functional groups show distinct response to nitrogen (N) addition, however, the patterns and underlying mechanisms across the natural N availability gradient remain unexplored. In present studies, effects of soil N fertility on aboveground N pools and production were examined, and the N: P stoichiometry was compared among forbs, graminoids, and legumes on an alpine grassland located in northeast of Qinghai-Tibet Plateau. Mean N: P ratios of the whole community in 2008 and 2009 were 9. 83 and 11.57, respectively, indicating that the sub-alpine grassland was mainly N-limited. The partial redundancy analysis (partial RDA) showed that the biomass percentage of forbs increased, while those of legumes and graminoids decreased with the soil N availability. It suggested that legumes and graminoids were more competitive than forbs in the natural N-limited grassland, which may be due to the N2-fixation ability and high nutrient use efficiency, respectively. Under the projected increasing N deposition, the vegetation tended to shift from graminoids and legumes to forbs. Significant relationships were found between the percentage of legumes biomass and N: P (phosphorus) ratio for the whole community and non-legumes, indicating that legumes could improve the community N status as well as non-legumes N status on the alpine grassland.
authors.forename: Ren-Yi
authors.initials: RY
authors.lastname: Zhang
authors.forename: Dang-Hui
authors.initials: DH
authors.lastname: Xu
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Chen
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
mesh_terms: D018533:Biomass; D065948:Grassland; D009584:Nitrogen / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D010944:Plants / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D018609:Tibet
chemical_list: D012987:Soil; D010758:Phosphorus; D009584:Nitrogen