Abstract: This study was aimed to investigate the effects of nitrogen deposition on soil nutrient and community biomass in alpine marsh meadows. The experiment was carried out in Fenghuoshan site. Soil nutrient and plant community biomass were studied under three nitrogen addition treatments (0,5 and 10 g N·m^-2·a^-1). The results showed that:The addition of exogenous nitrogen tended to acidify the soil of alpine swamp meadow,and changed the soil organic carbon and total nitrogen content,and significantly affected the absorption and utilization of soil nutrients by plants. Except for the significant increase of soil available nitrogen in the breeding season,the soil organic carbon and total nitrogen content decreased significantly in other periods. The aboveground biomass of the community increased;the total biomass and underground biomass decreased obviously in other periods except for the significant increase in the return green stage;However,the distribution proportion of the underground biomass in the whole growing season decreased with the increase of the nitrogen addition level. Correlation analysis showed that soil available nitrogen content was significantly correlated with plant community biomass and its distribution(P<0.01). In conclusion,Soil available nitrogen and plant community biomass in alpine swamp meadow in the headwaters region of the Yangtze River are sensitive to the change of soil nitrogen status. Adding nitrogen to alpine swampy meadow with lack of available nutrients can promote the growth of plant aerial part,thus chang the distribution pattern of photosynthetic products.

Key words: Nitrogen addition, Alpine swamp meadow, Soil nutrient, Community biomass, Biomass allocation

摘要： 为探讨氮沉降对高寒沼泽草甸土壤养分及其群落生物量的影响，本研究对风火山地区3种氮添加处理下（0，5和10 g N·m^-2·a^-1）土壤养分及植物群落生物量展开研究。结果显示：外源氮素添加使得沼泽草甸土壤趋向酸化、土壤有机碳及全氮含量发生改变，显著影响了植物对土壤养分的吸收利用，除繁殖期土壤有效氮显著增加外，其他时期显著降低；外源氮素添加使得群落地上生物量增加，总生物量与地下生物量除返青期显著增加外，其他时期明显减少；整个生长季地下生物量的分配比例随施氮的增加而下降；土壤有效氮含量与植物群落生物量及其分配均显著相关（P<0.01）。综上所述，长江源区高寒沼泽草甸土壤有效氮和植物群落生物量对土壤氮素状况的变化反应敏感，在有效养分匮乏的高寒沼泽草甸添加氮素能够促进植物地上部分的增长，从而改变其自身光合产物的分配模式。

关键词: 氮素添加, 高寒沼泽草甸, 土壤养分, 群落生物量, 地上、地下生物量分配