[1] Stevens C J, Dise N B, Mountford J O, et al. Impact of nitrogen deposition on the species richness of grasslands[J]. Science, 2004, 303: 1876−1879. doi:  10.1126/science.1094678
[2] Clark C M, Tilman D. Loss of plant species after chronic low-level nitrogen deposition to prairie grasslands[J]. Nature, 2008, 451: 712−717. doi:  10.1038/nature06503
[3] Knapp A K, Beier C, Briske D D, et al. Consequences of more extreme precipitation regimes for terrestrial ecosystems[J]. Bioscience, 2008, 58(9): 811−821. doi:  10.1641/B580908
[4] Elser J J, Bracken M E S, Cleland E E, et al. Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems[J]. Ecology Letters, 2007, 10(12): 1135−1142. doi:  10.1111/j.1461-0248.2007.01113.x
[5] Sardans J, Rivas-Ubach A, Peñuelas J. The C: N: P stoichiometry of organisms and ecosystems in a changing world: a review and perspectives[J]. Perspectives in Plant Ecology, Evolution and Systematics, 2012, 14(1): 33−47. doi:  10.1016/j.ppees.2011.08.002
[6] Cox P M, Betts R, Jones C D, et al. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model[J]. Nature, 2000, 408: 184−187. doi:  10.1038/35041539
[7] Wright I J, Westoby M. Nutrient concentration, resorption and lifespan: leaf traits of Australian sclerophyll species[J]. Functional Ecology, 2003, 17(1): 10−19. doi:  10.1046/j.1365-2435.2003.00694.x
[8] Craine J M, Tilman D, Wedin D, et al. Functional traits, productivity and effects on nitrogen cycling of 33 grassland species[J]. Functional Ecology, 2002, 16(5): 563−574.
[9] Cernusak L A, Winter K, Turner B L. Leaf nitrogen to phosphorus ratios of tropical trees: experimental assessment of physiological and environmental controls[J]. New Phytologist, 2010, 185(3): 770−779. doi:  10.1111/j.1469-8137.2009.03106.x
[10] Matzek V, Vitousek P M. N: P stoichiometry and protein: RNA ratios in vascular plants: an evaluation of the growth-rate hypothesis[J]. Ecology Letters, 2009, 12(8): 765−771. doi:  10.1111/j.1461-0248.2009.01310.x
[11] Niklas K J, Owens T, Reich P B, et al. Nitrogen/phosphorus leaf stoichiometry and the scaling of plant growth[J]. Ecology Letters, 2005, 8(6): 636−642. doi:  10.1111/j.1461-0248.2005.00759.x
[12] Baldwin D S, Mitchell A M. The effects of drying and re-flooding on the sediment and soil nutrient dynamics of lowland river-floodplain systems: a synthesis[J]. Regulated Rivers: Research & Management, 2000, 16(5): 457−467.
[13] Heidari M, Karami V. Effects of different mycorrhiza species on grain yield, nutrient uptake and oil content of sunflower under water stress[J]. Journal of the Saudi Society of Agricultural Sciences, 2014, 13(1): 9−13. doi:  10.1016/j.jssas.2012.12.002
[14] Ali Q, Haider M Z, Iftikhar W, et al. Drought tolerance potential of Vigna mungo L. lines as deciphered by modulated growth, antioxidant defense, and nutrient acquisition patterns[J]. Brazilian Journal of Botany, 2016, 39(3): 801−812. doi:  10.1007/s40415-016-0282-y
[15] Koerselman W, Meuleman A F M. The vegetation N: P ratio: a new tool to detect the nature of nutrient limitation[J]. Journal of Applied Ecology, 1996, 33(6): 1441−1450. doi:  10.2307/2404783
[16] Aerts R, Chapin Ⅲ F S. The mineral nutrition of wild plants revisited: a re-evaluation of processes and patterns[J]. Advances in Ecological Research, 1999, 30: 1−67.
[17] Stevens M H H, Shirk R, Steiner C E. Water and fertilizer have opposite effects on plant species richness in a mesic early successional habitat[J]. Plant Ecology, 2006, 183(1): 27−34. doi:  10.1007/s11258-005-9003-5
[18] Sterner R W, Elser J J. Ecological stoichiometry : the biology of elements from molecules to the biosphere[M]. Princeton: Princeton University Press, 2002.
[19] Gǜ sewell S. N:P ratios in terrestrial plants: variation and functional significance[J]. New Phytologist, 2004, 164: 243−266. doi:  10.1111/j.1469-8137.2004.01192.x
[20] 宾振钧, 王静静, 张文鹏, 等. 氮肥添加对青藏高原高寒草甸6个群落优势种生态化学计量学特征的影响[J]. 植物生态学报, 2014, 38(3):231−237. doi:  10.3724/SP.J.1258.2014.00020

Bin Z J, Wang J J, Zhang W P, et al. Effects of N addition on ecological stoichiometric characteristics in six dominant plant species of alpine meadow on the Qinghai-Xizang Plateau, China[J]. Chinese Journal of Plant Ecology, 2014, 38(3): 231−237. doi:  10.3724/SP.J.1258.2014.00020
[21] 王长庭, 王根绪, 刘伟, 等. 施肥梯度对高寒草甸群落结构、功能和土壤质量的影响[J]. 生态学报, 2013, 33(10):3103−3113. doi:  10.5846/stxb201202200232

Wang C T, Wang G X, Liu W, et al. Effects of fertilization gradients on plant community structure and soil characteristics in alpine meadow[J]. Acta Ecologica Sinica, 2013, 33(10): 3103−3113. doi:  10.5846/stxb201202200232
[22] Dong J, Cui X, Wang S, et al. Changes in biomass and quality of alpine steppe in response to N & P fertilization in the Tibetan Plateau[J/OL]. PLoS One, 2016, 11(5): e0156146 [2019−04−14]. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156146.
[23] Wang J, Wang Z, Zhang X, et al. Response of Kobresia pygmaea and Stipa purpurea grassland communities in northern Tibet to nitrogen and phosphate addition[J]. Mountain Research and Development, 2015, 35(1): 78−87. doi:  10.1659/MRD-JOURNAL-D-11-00104.1
[24] Yang Y, Gao Y, Wang S, et al. The microbial gene diversity along an elevation gradient of the Tibetan grassland[J]. The ISME Journal, 2014, 8(2): 430. doi:  10.1038/ismej.2013.146
[25] Wang C, Long R, Wang Q, et al. Fertilization and litter effects on the functional group biomass, species diversity of plants, microbial biomass, and enzyme activity of two alpine meadow communities[J]. Plant and Soil, 2010, 331(1−2): 377−389. doi:  10.1007/s11104-009-0259-8
[26] Tang L, Han W, Chen Y, et al. Resorption proficiency and efficiency of leaf nutrients in woody plants in eastern China[J]. Journal of Plant Ecology, 2013, 6(5): 408−417. doi:  10.1093/jpe/rtt013
[27] Lü X T, Han X G. Nutrient resorption responses to water and nitrogen amendment in semi-arid grassland of Inner Mongolia, China[J]. Plant and Soil, 2010, 327(1−2): 481−491. doi:  10.1007/s11104-009-0078-y
[28] Zhao G, Shi P, Wu J, et al. Foliar nutrient resorption patterns of four functional plants along a precipitation gradient on the Tibetan Changtang Plateau[J]. Ecology and Evolution, 2017, 7(18): 7201−7212. doi:  10.1002/ece3.3283
[29] 张方月. 高寒草甸生态系统碳循环对降雨梯度的响应及机理研究[D]. 北京: 中国科学院地理科学与资源研究所, 2018.

Zhang F Y. Responses of ecosystem carbon cycle to precipitation gradient in an alpine meadow [D]. Beijing: Institute of Geographic Sciences and Natural Resources Research, 2018.
[30] Borer E T, Harpole W S, Adler P B, et al. Finding generality in ecology: a model for globally distributed experiments[J]. Methods in Ecology and Evolution, 2014, 5(1): 65−73. doi:  10.1111/2041-210X.12125
[31] Smith M, Sala O, Phillips R. Drought-Net: a global network to assess terrestrial ecosystem sensitivity to drought[EB/OL]. [2019−03−14]. http://asm2015.lternet.edu/working-groups/drought-net-global-network-assess-terrestrial-ecosystem-sensitivity-drought.
[32] Güsewell S. Responses of wetland graminoids to the relative supply of nitrogen and phosphorus[J]. Plant Ecology, 2005, 176(1): 35−55. doi:  10.1007/s11258-004-0010-8
[33] Chapin Ⅲ F S, Shaver G R, Giblin A E, et al. Responses of arctic tundra to experimental and observed changes in climate[J]. Ecology, 1995, 76(3): 694−711. doi:  10.2307/1939337
[34] Shaver G R, Bret-Harte M S, Jones M H, et al. Species composition interacts with fertilizer to control long-term change in tundra productivity[J]. Ecology, 2001, 82(11): 3163−3181. doi:  10.1890/0012-9658(2001)082[3163:SCIWFT]2.0.CO;2
[35] Mack M C, Schuur E A G, Bret-Harte M S, et al. Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization[J]. Nature, 2004, 431: 440−443. doi:  10.1038/nature02887
[36] DeMalach N, Zaady E, Kadmon R. Contrasting effects of water and nutrient additions on grassland communities: a global meta-analysis[J]. Global Ecology and Biogeography, 2017, 26(8): 983−992. doi:  10.1111/geb.12603
[37] Niklaus P A, Leadley P W, Stöcklin J, et al. Nutrient relations in calcareous grassland under elevated CO2[J]. Oecologia, 1998, 116(1−2): 67−75. doi:  10.1007/s004420050564
[38] Han W, Luo Y, Du G. Effects of clipping on diversity and above-ground biomass associated with soil fertility on an alpine meadow in the eastern region of the Qinghai-Tibetan Plateau[J]. New Zealand Journal of Agricultural Research, 2007, 50(3): 361−368. doi:  10.1080/00288230709510304
[39] Chaves M M, Maroco J P, Pereira J S. Understanding plant responses to drought:from genes to the whole plant[J]. Functional Plant Biology, 2003, 30(3): 239−264. doi:  10.1071/FP02076
[40] Klein J A, Harte J, Zhao X Q. Experimental warming causes large and rapid species loss, dampened by simulated grazing, on the Tibetan Plateau[J]. Ecology Letters, 2004, 7(12): 1170−1179. doi:  10.1111/j.1461-0248.2004.00677.x
[41] Bedia J, Busqué J. Productivity, grazing utilization, forage quality and primary production controls of species-rich alpine grasslands with N ardus stricta in northern S pain[J]. Grass and Forage Science, 2013, 68(2): 297−312. doi:  10.1111/j.1365-2494.2012.00903.x
[42] Li H, Zhang F, Li Y, et al. Thirty-year variations of above-ground net primary production and precipitation-use efficiency of an alpine meadow in the north-eastern Qinghai-Tibetan Plateau[J]. Grass and Forage Science, 2016, 71(2): 208−218. doi:  10.1111/gfs.12165
[43] He J S, Wang L, Flynn D F B, et al. Leaf nitrogen: phosphorus stoichiometry across Chinese grassland biomes[J]. Oecologia, 2008, 155(2): 301−330.
[44] Henry H A L, Cleland E E, Field C B, et al. Interactive effects of elevated CO2, N deposition and climate change on plant litter quality in a California annual grassland[J]. Oecologia, 2005, 142(3): 465−473. doi:  10.1007/s00442-004-1713-1
[45] Xia J, Wan S. Global response patterns of terrestrial plant species to nitrogen addition[J]. New Phytologist, 2008, 179(2): 428−439. doi:  10.1111/j.1469-8137.2008.02488.x
[46] Li J, Yang C, Liu X, et al. Inconsistent stoichiometry response of grasses and forbs to nitrogen and water additions in an alpine meadow of the Qinghai-Tibet Plateau[J]. Agriculture, Ecosystems & Environment, 2019, 279: 178−186.
[47] Liu P, Huang J, Han X, et al. Differential responses of litter decomposition to increased soil nutrients and water between two contrasting grassland plant species of Inner Mongolia, China[J]. Applied Soil Ecology, 2006, 34(2−3): 266−275. doi:  10.1016/j.apsoil.2005.12.009
[48] Wang C, Wan S, Xing X, et al. Temperature and soil moisture interactively affected soil net N mineralization in temperate grassland in northern China[J]. Soil Biology and Biochemistry, 2006, 38(5): 1101−1110. doi:  10.1016/j.soilbio.2005.09.009
[49] 范丙全, 胡春芳. 灌溉施肥对壤质潮土硝态氮淋溶的影响[J]. 植物营养与肥料学报, 1998, 4(1):16−21. doi:  10.3321/j.issn:1008-505X.1998.01.003

Fan B Q, Hu C F. Effects of irrigation and fertilization on nitrate leaching in loamy fluvo-aquic soil[J]. Plant Nutrition and Fertilizer Science, 1998, 4(1): 16−21. doi:  10.3321/j.issn:1008-505X.1998.01.003
[50] Scholefield D, Tyson K C, Garwood E A, et al. Nitrate leaching from grazed grassland lysimeters: effects of fertilizer input, field drainage, age of sward and patterns of weather[J]. Journal of Soil Science, 1993, 44(4): 601−613. doi:  10.1111/j.1365-2389.1993.tb02325.x
[51] Ding K, Zhong L, Xin X P, et al. Effect of grazing on the abundance of functional genes associated with N cycling in three types of grassland in Inner Mongolia[J]. Journal of Soils and Sediments, 2015, 15(3): 683−693. doi:  10.1007/s11368-014-1016-z
[52] Liu H, Mi Z, Lin L, et al. Shifting plant species composition in response to climate change stabilizes grassland primary production[J]. Proceedings of the National Academy of Sciences, 2018, 115(16): 4051−4056. doi:  10.1073/pnas.1700299114
[53] Luo X, Mazer S J, Guo H, et al. Nitrogen: phosphorous supply ratio and allometry in five alpine plant species[J]. Ecology and Evolution, 2016, 6(24): 8881−8892. doi:  10.1002/ece3.2587
[54] Zhang J, Yan X, Su F, et al. Long-term N and P additions alter the scaling of plant nitrogen to phosphorus in a Tibetan alpine meadow[J]. Science of the Total Environment, 2018, 625: 440−448. doi:  10.1016/j.scitotenv.2017.12.292
[55] Mamolos A P, Vasilikos C V, Veresoglou D S. Vegetation in contrasting soil water sites of upland herbaceous grasslands and N: P ratios as indicators of nutrient limitation[J]. Plant and Soil, 2005, 270(1): 355−369. doi:  10.1007/s11104-004-1793-z
[56] Rejmánková E, Macek P, Epps K. Wetland ecosystem changes after three years of phosphorus addition[J]. Wetlands, 2008, 28(4): 914−927. doi:  10.1672/07-150.1