Abstract: Nitrogen(N) and phosphorous(P) influence the growth,development,structure and function of any terrestrial ecosystem.Ecological stoichiometry of plant N and P provides the dominant means for investigating plant nutrient utilization.Leaf N and P stoichiometry of main species in typical steppes of China was reported through systematic census of 33 dominant species within 132 research sites along a grassland transect.Transect includes the main grassland types in both northern temperate zones and Tibet Plateau of China.Results showed the average of N,P,N/P for all species was 18.18±6.16mg·g^-1,1.25±0.64 mg·g^-1 and 16.75±6.67,respectively.N and P were significantly positive correlation(P<0.05).No significant difference was found in either N or P content between C₃ and C₄ species(P<0.05).Nitrogen and phosphorus content of dicotyledons,forbs,legumes and mesad were higher than that observed for monocotyledons,gramineae,nonlegumes and siccocolous.The N/P of C₃,dicotyledons,gramineae,legumes and siccocolous were higher than that of C₄,monocotyledon,forbs,nonlegume and mesad.In general,N and P content of alpine steppes were higher while the N/P was lower than that of temperate steppes.Systemic studies of leaf nitrogen and phosphorus in different plant functional groups may provide a valuable reference for investigations of limited elements and adaptation strategies of grassland ecosystem.

Key words: N, P, Stoichiometry, Plant functional types, Temperate steppes, Alpine steppes

摘要： 氮(N)和磷(P)影响陆地生态系统的植物生长、发育和系统的结构和功能等,而植物氮磷(NP)生态化学计量特征为研究植物的养分利用状况提供了重要的手段,不同功能群植物叶片N、P元素的系统研究将为草地生态系统植被的限制元素及其对环境的适应策略提供参考依据。因此,以涵盖中国北方温带草原区和青藏高原区主要草地类型的草地样带为平台,通过系统采集该样带上132个采样点的33个主要优势植物叶片,分析了中国典型草地植物叶片N和P的生态化学计量学特征。结果表明:样带上主要物种的N含量、P含量、N/P的均值分别为18.18±6.16 mg·g^-1、1.25±0.64 mg·g^-1和16.75±6.67。其中,N和P存在显著的正相关关系(P<0.05);C₃植物和C₄植物的N、P含量无明显差异;双子叶植物、非禾本科植物、豆科植物、中生型植物的N、P含量分别高于相应的单子叶植物、禾本科植物、非豆科植物、旱生型植物;C₃植物、双子叶植物、禾本科植物、豆科植物、旱生植物的N/P分别高于相应的C₄植物、单子叶植物、非禾本科植物、非豆科植物、中生植物。总之,高寒草地植物的N、P含量高于温性草地植物,但其N/P却低于温性草地。

关键词: 氮, 磷, 化学计量学, 功能群, 温性草原, 高寒草原