高寒草地不同退化程度下土壤微生物及土壤酶活性变化特征

为探讨不同退化程度对高寒草地土壤微生物及土壤酶活性的影响,以青藏高原东北缘祁连山3种不同退化程度(轻度退化、中度退化、重度退化)高寒草地为研究对象,测定和分析土壤3大类微生物(细菌、真菌、放线菌)和氮素生理群(氨化细菌、好气性固氮菌、嫌气固氮菌、硝化细菌、反硝化细菌)数量、微生物量(碳、氮)及土壤酶活性(蔗糖酶、脲酶、磷酸酶、过氧化氢酶)变化特征。结果表明:(1)相同土层不同退化程度,土壤3大类微生物数量、氮素生理群、微生物量以及土壤酶活性随退化程度的加重总体呈减小的趋势,重度退化程度下各指标含量最小,中等退化程度可增加10—20cm土壤放线菌、氨化细菌及反硝化细菌数量和20—30cm土壤细菌、真菌、放线菌、好气性固氮菌、反硝化细菌数量;(2)不同土层相同退化程度,土壤3大类微生物数量、氮素生理群、微生物量以及土壤酶活性随土层深度的加深均逐渐减小。研究结果对评价草地退化程度提供了新思路,同时为高寒草地的恢复和重建提供了重要的理论依据。

Characteristics of Soil Microorganism and Soil Enzyme Activities in Alpine Meadows under Different Degrees of Degradation

To explore the effects of different degrees of degradation on soil microbes and soil enzyme activities in alpine meadows,lightly degraded grassland,moderate degraded grassland and severe degraded grassland of alpine grasslands in the Qilian Mountains of the northeastern Qinghai-Tibet Plateau were chosen as the research objects.Characteristic changes of the number of soil microbes (bacteria,fungus,and actinomycetes),soil nitrogen bacteria groups (ammonifier,aerobic nitrogen fixing bacteria,anaerobic nitrogen fixing bacteria,nitrifiers,and denitrifying bacteria),soil microbial biomass (soil microbial biomass carbon and soil microbial biomass nitrogen),and soil enzyme activities (sucrose,urease,phosphatase,and catalase) were determined and analyzed in alpine meadows under different degrees of degradation.The results showed that,for the same soil layer under different degrees of degradation,the number of soil microbes,soil microbial biomass,soil nitrogen bacteria groups,and soil enzyme activities decreased with the increase of degradation degree,and each index was the lowest under severe degradation.The number of actinomycetes,ammoniated bacteria,and denitrifying bacteria in the 10-20 cm soil layer,and the number of bacteria,fungi,actinomycetes,aerobic nitrogen fixing bacteria and denitrifying bacteria in the 20-30 cm soil layer increased in the moderate degraded grassland (p ＜ 0.05).For different soil layers under under the same degrees of degradation,the number of soil microbes,soil nitrogen bacteria groups,soil microbial biomass,and soil enzyme activities decreased with the increase of soil depth.These results provide a new method for assessing the degradation of grasslands,and thus offering important theoretical bases for the restoration of degraded alpine meadows.