中文摘要：

通过稀释平板法和常规化学分析法,对伊犁河谷地区3种龄级（5年、10年、15年）的速生杨欧美黑杨（Populus×euramericana）人工林的土壤微生物数量、组成和土壤养分变化进行了研究。结果表明,3种不同林龄林地土壤微生物集中分布在10-40cm土层,数量和种类组成随季节变化有明显差异。随着林龄的增长,土壤微生物总数、细菌数量减少,真菌和放线菌数量在10年生人工林最高,这一规律随季节变化。三大类土壤微生物的组成比例相对稳定,不随季节变化而变化。土壤有机碳、氮含量主要集中在0-20cm土层,随土壤深度的增加逐渐减少,其含量及分布受季节和土壤深度不同程度的影响。土壤有机碳含量随林龄的增长而逐渐增高,有机氮则先减后增。相关分析表明,土壤微生物总数与土壤有机碳呈负相关,真菌数量与土壤有机氮呈正相关。3种林地土壤有机C/N比与土壤细菌数量/真菌数量比例一致,说明速生杨人工林在一定生长年龄内能提高土壤的固碳能力,改善土壤肥力。

英文摘要：

Aims Our objective was to better understand the distribution and seasonal dynamics of soil microorganisms and soil nutrients of fast-growing Populus （Populus × euramericana） plantations of different ages （5,10 and 15 years） in Yili Xinjiang,China.Methods We investigated the number and species composition of soil microorganisms and organic carbon/nitrogen by means of plate count and conventional chemical methods,respectively.Important findings The three plantation forests were significantly different in microbial numbers and species compositions as affected by soil depth and season.The soil microbes were mainly distributed at 10-40 cm,and bac-teria accounted the largest proportion.The total number of microorganisms and bacteria decreased with age,but the 15-year forest had the highest number of fungi and actinomycetes.The ratio of three kinds of microbial communities was relatively stable in soil and did not change with season.The content of soil organic carbon and nitrogen was mainly concentrated at 0-20 cm,decreased with increasing soil depth and responded differently to change of seasons and soil depth.Soil organic carbon increased with stand age,while nitrogen decreased and then increased.The cor-relation between soil microbes and soil organic carbon was negative,and the correlation between number of fungi and soil organic nitrogen was positive.The ratio of soil organic C/N was consistent with the ratio of bacteria num-ber/actinomycetes number,illustrating poplar plantation forests fix carbon and improve soil fertility.