中文摘要：

采用熏蒸-提取法、微生物培养法,研究了荒漠灌区不同种植年限紫花苜蓿（Medicagosativa L.‘Gannong No.3’）草地0～60cm土层土壤微生物量和数量,从土壤微生物的角度对荒漠灌区苜蓿的退化机理、人工草地管理做出了评价。结果表明,不同种植年限苜蓿草地土壤微生物量碳、氮及微生物（细菌、真菌、放线菌）数量均呈现随土层深度的增加而减小的趋势;随苜蓿种植年限的增加,土壤微生物量碳、氮,细菌和放线菌数量均呈增加-降低-增加的变化趋势,真菌数量呈先增加后降低的变化趋势;土壤微生物群落以细菌占绝对优势（70.72%）,真菌最少（0.18%）,微生物总数量和微生物生物量均大于撂荒地,且5年生苜蓿地微生物总数最多,是其他各种植年限的1.58～6.17倍,且微生物生物量碳、氮与细菌、放线菌数量呈极显著正相关。微生物生物量及数量表现出明显的季节动态,除土壤真菌数量最大值出现在9月份之外,其余指标最大值均出现在7月份,最小值在4月份。

英文摘要：

Using fumigation extraction method and microbial culture method, this paper investigated the microbial biomass and soil microbial quantities of alfalfa field in 0~60 cm soil layer with different growing years （0,3,4,5,7,10 years） in desert irrigation area. Meanwhile, the relationships between soil microbial biomass and soil microbial quantities were studied by correlation analysis, and alfalfa with different plant- ing years was evaluated from the aspect of soil microbes. The results indicated that soil microbial biomass carbon, soil microbial biomass nitrogen, and 3 main categories of soil microorganisms （fungi, bacteria and actinomycetes） decreased significantly with the increase of soil depth; soil microbial biomass carbon, soil microbial biomass nitrogen, bacteria and actinomycetes increased firstly, and then decreased, and then in- creased with the increase of cropping years~ fungi increased, and then decreased with the increase of crop- ping years. The number of bacteria was the highest （70.72%） and fungi was lowest （0.18~） among the microorganisms. Contrasted with abandoned land, the total microbial count and microbial biomass were all increased in various cropping-year alfalfa field, and were the highest in five-year alfalfa field. The seasonal dynamic of soil microbial biomass and soil microbial quantities was apparent. The maximum number of soil microbial biomass and soil microbial quantities was observed in July, and the minimum in April, except for fungi, which the maximum number was observed in September.