Abstract: We studied the nematode community characteristics at different soil depths under Caragana microphylla shrub canopies versus in open areas. The results showed that the quantity and diversity of soil nematodes under shrub canopies were higher than those in open areas. There were decreasing trends for both quantity and diversity of soil nematodes as soil depth increased,which indicated obvious surface aggregation patterns for the vertical distributions of soil nematode communities. Under shrub canopies,the mature index (MI) at the top layer of soil (0-10 cm) was the lowest,which indicated that there was a relatively stable soil environment in this soil layer. For both the maturity index of plant parasitic nematodes (PPI) under shrub canopies and in open areas,there were decreasing trends as soil depth increased. At the top layer of soil under shrub canopies,the abundance of free-living nematodes was the highest;the enrichment index (EI) was relatively high;the structure index (SI) was the largest,which indicated that there was a stable environment with low levels of disturbances. The channel index (CI) at the top layer of soil under shrub canopies was less than 50. In contrast,the CI values in other treatments were all greater than 50,which indicated that the decomposition pathways of organic matters for nematodes at the top layer of soil under shrub canopies were mainly bacterial channels. The abundance of microbivorous nematodes under shrub canopies was significantly greater than that in open areas. The proportion of predatory omnivorous nematodes under shrub canopies was not significantly different from that in open areas,suggesting that shrub canopies did not affect the complexity of soil food webs. In conclusion,C. microphylla shrub canopies affected the composition,diversity and functionality of soil nematode communities in the desert steppe via influencing soil recourses.

Key words: Caragana microphylla, Soil nematodes, Vertical distribution, Diversity, Functionality

摘要： 本研究比较了小叶锦鸡儿灌丛内外部及不同土层土壤线虫群落特征。结果表明：灌丛内土壤线虫数量和多样性高于灌丛外，且随土壤深度增加均呈下降趋势，土壤线虫群落垂直分布具有明显表聚性。灌丛内表层土自由生线虫成熟度指数最低，这说明灌丛内表层土具有相对稳定的土壤环境；随土壤深度的增加，灌丛内外植物寄生线虫成熟度指数均呈下降趋势。表层土自由生活线虫丰富度最大，富集指数相对较高，结构指数最大，说明灌丛内表层土环境稳定，受干扰程度较低；灌丛内表层土土壤线虫通道指数小于50，其余处理通道指数均大于50，说明灌丛内表层土土壤线虫分解有机物以细菌通道为主。灌丛内食微线虫丰富度明显大于灌丛外，捕食杂食类线虫比例没有显著变化，说明灌丛并未影响土壤食物网的复杂性。小叶锦鸡儿灌丛通过影响灌丛土壤资源影响土壤线虫的群落组成、多样性和功能性。

关键词: 小叶锦鸡儿, 土壤线虫, 垂直分布, 多样性, 功能性