【作者】 刘艳；

【导师】 任飞；

【作者基本信息】 青海大学 ， 生态学， 2023， 硕士

【摘要】 全球气候和环境变化背景下,青藏高原高寒草甸土壤氮、磷的可利用性正在发生快速变化,进而对高寒草甸相关的碳汇、养分循环和生态系统功能产生深刻影响。氮、磷可利用性增加对群落结构、组成及生产力影响的交互作用机制尚不清楚。本研究依托海北高寒草地生态系统国家野外科学观测研究站开展了多梯度的氮磷添加组合实验,设置氮添加梯度(0,50,100,150,200 kg·ha^-1·a^-1)、磷添加梯度(0,25,50,75,100 kg·ha^-1·a^-1),氮磷梯度相互组合共25个处理其中对照为（N0P0）,每个处理分别设置了4个重复（Block）,探讨了持续养分添加的第3年,高寒草甸群落、功能群水平多样性指数、植物性状及地上和地下生物量对多梯度氮磷添加的响应情况,主要结果如下:1)氮、磷添加会造成群落结构和组成的改变。氮添加、磷添加及氮磷混合添加均显著降低群落多样性（P<0.001）,氮、磷之间具有协同降低效应;不同功能群多样性指数对氮磷添加的响应虽存在差异,但整体均下降,较高的氮磷混合添加使群落趋于禾草化。2)氮、磷添加使群落植物性状发生改变。氮添加、磷添加及氮磷混合添加均会显著增加群落植物平均高度（P<0.001）,分别增加26.4%、37.6%、55.3%;降低群落植物总盖度（P<0.001）,降幅分别为3.7%、6.9%、48.4%;单独氮添加会使群落多度增加35.8%,而磷添加、氮磷混合添加会使群落多度分别降低23.8%、42.8%。3)群落氮磷养分及化学计量显著改变。氮添加显著提高植物全氮含量（P<0.001）,磷添加显著提高了植物全磷含量（P<0.001）,磷添加对植物氮磷比的负效应大于氮添加对氮磷比的正效应。4)氮添加、磷添加及氮磷混合添加均会显著增加群落地上生物量（P<0.001）,增幅分别为39.9%、25.2%、83.7%,氮、磷之间具有协同增效作用;磷添加使地下生物量增加约21.9%,氮添加使地下生物量降低8.8%,而氮磷混合添加使其降幅达27.7%;氮磷混合添加促使植物生物量分配向地上部分增加,地下部分减少,因而根冠比下降。5)群落平均高度与地上生物量呈显著的正相关关系,群落各多样性指数均与其呈显著负相关关系。6)群落中各功能群植物所受限制养分不同,青藏高原高寒草甸植物生长趋向于氮磷共同限制。更多还原

【Abstract】 Against the backdrop of global climate and environmental change,the availability of nitrogen and phosphorus in soil of alpine meadows on the Qinghai Tibet Plateau is rapidly changing,which in turn has a profound impact on carbon sinks,nutrient cycling,and ecosystem functions related to alpine meadows.The interactive mechanism of the increased availability of nitrogen and phosphorus on community structure,composition,and productivity is still unclear.This study conducted a multi gradient nitrogen and phosphorus addition combination experiment based on The Northwest Institute of Plateau Biology,Chinese Academy of Science.The control（N0P0）,nitrogen addition gradient(0,50,100,150,200 kg·ha^-1·a^-1),and phosphorus addition gradient(0,25,50,75,100 kg·ha^-1·a^-1)were set up,with a total of 25 treatments of nitrogen and phosphorus gradient combinations.Each treatment was set up with 4 replicates（Blocks）,Explored the response of alpine meadow communities,functional group level diversity index,plant traits,and aboveground and underground biomass to multi gradient nitrogen and phosphorus addition in the third year of continuous nutrient addition.The results indecated that:1)The addition of nitrogen and phosphorus can cause changes in community structure and composition。Nitrogen addition,phosphorus addition,and nitrogen phosphorus mixed addition all significantly reduced community diversity（P<0.001）,there is a synergistic reduction effect between nitrogen and phosphorus;Although there are differences in the response of diversity indices of different functional groups to nitrogen and phosphorus addition,the overall decrease is observed.The higher nitrogen and phosphorus mixed addition leads to the community tending towards grassification.2)The addition of nitrogen and phosphorus causes changes in plant traits in the community。Nitrogen addition,phosphorus addition,and nitrogen phosphorus mixed addition all significantly increased the average height of community plants（P<0.001）,increasing by 26.4%,37.6%,and 55.3%,respectively;Reduce the total plant coverage of the community（P<0.001）by 3.7%,6.9%,and 48.4%,respectively;Single nitrogen addition can increase community abundance by 35.8%,while phosphorus addition and nitrogen phosphorus mixed addition can reduce community abundance by 23.8%and42.8%,respectively.3)Significant changes in community nitrogen and phosphorus nutrients and stoichiometry。nitrogen addition significantly increased the total nitrogen content of plants（P<0.001）,while phosphorus addition significantly increased the total phosphorus content of plants（P<0.001）.The negative effect of phosphorus addition on plant nitrogen phosphorus ratio was greater than the positive effect of nitrogen addition on nitrogen phosphorus ratio.4)The addition of nitrogen,phosphorus,and mixed nitrogen and phosphorus significantly increased the aboveground biomass of the population（P<0.001）,with an increase of 39.9%,25.2%,and 83.7%,there is a joint promoting effect between nitrogen and phosphorus;Phosphorus addition increased underground biomass by about 21.9%,nitrogen addition reduced underground biomass by 8.8%,and mixed nitrogen and phosphorus addition reduced it by 27.7%;The mixed addition of nitrogen and phosphorus promotes an increase in plant biomass distribution towards the aboveground part and a decrease in the underground part,resulting in a decrease in root to shoot ratio.5)The average height of the community is significantly positively correlated with aboveground biomass,while the diversity indices of the community are significantly negatively correlated with it.6)Different functional groups of plants are subject to different limiting nutrients,and the growth of alpine meadow plants in the Qinghai Tibet Plateau tends to be jointly limited by nitrogen and phosphorus.更多还原