采用增温棚模拟增温的方法,对比研究了青藏高原腹地的风火山地区典型的高寒沼泽和高寒草甸在两种增温梯度条件下的土壤养分状况、微生物生物量碳氮和酶活性对温度升高的响应。结果表明:(1)模拟增温显著提高了增温棚内的气温和5 cm土壤温度,高寒沼泽草甸区不封顶增温棚平均气温和5 cm土壤温度分别较对照升高2.54℃和0.68℃,封顶增温棚平均气温和5 cm土壤温度分别较对照提高4.99℃和1.43℃;高寒草甸区内不封顶和封顶增温棚5 cm土壤平均温度分别较对照提高0.31℃和3.93℃。(2)模拟增温对两种草甸土壤养分含量的变化表现不一致,高寒沼泽草甸中开顶和封顶式增温棚0~5 cm土层中土壤有机碳和全氮含量降低,5~20 cm土层中却增加;相反的,高寒草甸中开顶和封顶式增温棚0~5 cm土层中土壤有机碳和全氮含量增加,5~20 cm土层中减少。(3)模拟增温显著提高了土壤微生物生物量碳、氮的含量,但由于封顶式增温棚增温幅度过大,抑制了微生物的代谢活动,导致微生物生物量碳、氮降低。(4)模拟增温使土壤过氧化氢酶、脲酶和蛋白酶的活性在两种草甸中均有不同程度的提高,碱性磷酸酶活性减小,蔗糖酶活性在两种草甸中表现出不一致的变化情况。同时,封顶增温棚内的过氧化氢酶、脲酶和蛋白酶活性增加的幅度,蔗糖酶和碱性磷酸酶减少的幅度均小于开顶式增温棚内的酶活性。两种草甸土壤有机碳和全氮含量的变化对模拟增温的响应情况不一致,这与不同类型草甸中土壤理化性质、水热状况、土壤代谢、植物种类及土壤生物(动物和微生物)区系、数量和生物多样性等因子有关。

To investigate effects of warming on soil nutrients,microbes and soil enzyme activities in alpine meadow and alpine swamp meadow in the hinterland of the Qinghai-Tibet Plateau of China,an experiment was carried out from August 2006 to September 2008 using open-top chambers and capped chambers for comparison.Results show that(1) in alpine swamp meadow,warming increased the average air temperature by 2.54 ℃,and the soil temperature within the depth of 5 cm by 0.68℃ in the open-top chambers and by 4.99℃ and by 14.3℃,respectively,in the closed chambers;while in alpine meadow,it increased soil temperature by 0.31℃ and by 3.93℃ in the open-top chambers and closed chambers,respectively.(2) soil nutrients in the two meadows responded differently to warming.In the alpine swamp meadow,soil organic carbon and total nitrogen decreased in the soil layer 0~5 cm in depth,but increased in the soil layer 5~20 cm in depth in both chambers,while in the alpine meadow,they increased in the soil layer 0-5cm in depth,but decreased in the soil layer 5~20 cm in depth.(3) warming significantly increased carbon and nitrogen contents in soil microbial biomass,but the greater magnitude of the temperature rise in the closed chambers suppressed metabolism of soil microbes,thus leading to decrease in carbon and nitrogen contents in microbial biomass.(4) The activities of catalase,urease and proteinase increased to a various extent in two meadow soils,but the activity of alkaline phosphatase decreased,and saccharase responded differently between the two meadow soils.The increase in activities of catalase,urease and proteinase and the decrease in saccharase and alkaline phosphatase in the closed chambers were less in magnitude than in the open-top chamber,which is similar to the variation trend of the population of soil microbes.The different responses of soil organic carbon and total N to warming is attributed to difference between the two meadows in soil properties,hydrothermal regime,soil metabolism,vegetation,soil fauna(animal and microbe),population and micro-biodiversity.