在三江源区研究了不同施肥梯度对高寒矮嵩草草甸群落结构、功能;土壤全量养分、速效养分;土壤有机碳和微生物生物量碳的影响,以揭示矮嵩草草甸群落特征;土壤养分和土壤微生物活性对施肥梯度的响应。结果表明:1)随着施肥量的增加,不同功能群的盖度响应各异,其中禾本科植物的响应较大,而豆科和杂类草植物盖度明显降低,莎草科盖度变化不明显;施肥量增加到一定程度,如施氮40 g/m~2时,各功能群植物的盖度逐渐降低。生物量随施肥梯度呈单峰曲线变化,不施肥时生物量最低,施肥20 g/m~2或32 g/m~2时生物量最高。2)土壤全量养分和速效养分在施肥量为20 g/m~2或32 g/m~2时较高,施肥量增加到40 g/m~2时土壤资源逐渐降低。3)不同施肥梯度矮嵩草草甸土壤有机碳和微生物生物量碳在0-10 cm土层明显较高,且随着施肥量的增加,分布在0-40 cm土层的土壤有机碳含量呈单峰曲线变化。施肥20 g/m~2或32 g/m~2时土壤有机碳和微生物量碳含量最高。4) 30 g/m~2施肥量可作为高寒草甸最佳施氮水平。施肥梯度下土壤有机碳和微生物量碳含量可作为衡量土壤肥力和土壤质量变化的重要指标。高施肥量(≥40 g/m~2)视为影响高寒草甸生态系统结构与功能、土壤养分及土壤微生物活性的阈值。

In order to explain the alpine meadow plant community characteristics and the response of soil nutrient and soil microbial activity to fertilizer gradients in Kobresia humilis meadow. Effects of different fertilizer gradients on the structure,function of plant community,contents of total soil nutrients and available nutrients,soil organic carbon and microbial biomass carbon in the K. humilis meadow were studied in Three-river Headwater Areas of Qinghai-Tibetan Plateau,China. The results showed that. 1) With the increase of fertilizer application,the coverage in different functional groups response differently. Among which the coverage of grasses function group increased a lot,while legumes and forbs function group coverage decreased obviously,there were no obvious variation in the coverage of sedges function group; however,the coverage of each plant function group will be reduce gradually when fertilizer application increased to a certain degree,for example,when N fertilizer application reached 40 g/m~2. Plant function group biomass showed unimodal curve changes with different fertilizer gradients and the biomass reached the minimum under unfertilizing conditions and the maximum when 20 g/m~2 or 32 g/m~2. 2) The contents of total soil nutrients and available nutrients are higher when fertilizer application is 20 g/m~2 or 32 g/m~2 and soil resource will be reduced gradually when soil application increase to 40 g/m~2. 3) Soil organic carbon and microbial biomass carbon of different fertilizer gradients in the K. humilis meadow were obviously higher at 0-10 cm soil layer,and the contents of the soil organic carbon at 0-40 cm soil layer showed unimodal curve variation with increasing N fertilizer application. The highest value of soil organic carbon and microbial biomass carbon were occurred in 20 g/m~2or 32 g/m~2 conditions. 4) Fertilizer application with 30 g/m~2 can be the best nitrogen level to alpine meadow. The contents of soil organic carbon and microbial biomass carbon under fertilizer gradients can be an important indicator to evaluate soil fertility and soil quality variation. The content N fertilizer application (≥40 g/m~2) which is used as a threshold to influence ecosystem structure,function,soil nutrient,and soil microbial activities in alpine meadow.