摘要:在野外调查的基础上，采用干筛法和改良的Baermann漏斗法，研究植茶年限（19年、26年、34年和56年）对土壤团聚体线虫群落结构的影响。本研究共捕获线虫6602条，隶属于46属，以Acrobeloides为优势属，食细菌线虫为优势营养类群。线虫总数和大多数营养类群数量均随植茶年限的延长先升高后降低，在植茶26年时数量达到最高，且随粒径的减小而减少。线虫类群数则随着植茶年限的延长，虽随着粒径的减小而减少，但对 > 2 mm粒径团聚体中响应不敏感。线虫结构指数（Structure index，SI）多数小于50，富集指数（Enrichment index，EI）均大于50。随着植茶年限的延长，茶园生态系统土壤食物网逐渐退化；与大粒径团聚体相比， < 0.25 mm粒径团聚体中食物网受扰动相对较小。以上结果表明，植茶26年土壤更适合线虫繁殖且大粒径团聚体更有利于线虫生存；随着植茶年限的延长，土壤食物网退化， < 0.25 mm粒径团聚体受到的干扰较少，这一结果有助于揭示茶园土壤团聚体中线虫群落变化和土壤食物网对植茶年限的响应特征。



Abstract:This study began in July 2018 at Zhongfeng long-term agricultural research site of Sichuan Agricultural University in Ya'an, Sichuan, China. The prevailing climate surrounding the study site is a subtropical monsoon climate. Mean annual temperature is 15.4℃, with the lowest and highest mean daily temperatures of 4.3℃ and 35.2℃, respectively. Mean annual precipitation is 1500 mm with 72.6% of the precipitation occurring during July and September. The layer being exposed belongs to sedimentary rock predominantly formed since the Mesozoic age, with the soil being Luvisols with a texture of clay loam. "Sichuan tea" has been cultivated since 1950s, forming a large-scale tea plantation with different ages. As a useful approach, the space-for-time substitution method is often used to monitor soil changes occurring along a tea plantation chronosequence that has developed with similar soils and similar climatic conditions. Establishment of tea plantations at different times creates an opportunity for elucidating the tea planting process because the geomorphologic processes can determine soil conditions before tea planting. In order to explore the effects of tea plantation age on the soil nematode community characteristics within soil aggregate and provide theoretical basis for formulating scientific and reasonable soil management measures in tea plantations, soil samples were obtained from tea plantations with different ages (19, 26, 34 and 56 a). The four tea plantations were collected on similar geomorphologic units, slope direction and gradient, and fertilization practices Soil aggregates were separated into four fractions:large (> 2 mm), medium (2-1 mm), small macro-aggregates (1-0.25 mm), and micro-aggregates (< 0.25 mm). The nematodes were extracted from 50 g fresh soil by a modified Baermann funnel methodology. In this study, a total of 6602 nematodes were captured, which belonged to 46 genera and the mean density was 421 ind·100g^-1 dry soil. Acrobeloides was the dominant genus and bacterial nematodes were the dominant trophic group. Soil aggregate-associated total nematode abundance decreased significantly with decreasing of aggregate size regardless of the tea plantation age. Additionally, the abundance of different trophic groups (including bacterivores, plant-parasites and fungivores) showed a trend similar to the abundance of total nematodes within different aggregates. In the macro-aggregates, the abundance of total nematodes as well as different trophic groups, with the exception of omnivores-predators, was significantly higher in the 26a tea plantation compared to that in other plantations. In the micro-aggregates, on the contrary, no significant differences were observed among the different aged tea plantations. Nematode structure index (SI) was less than 50, and enrichment index (EI) was more than 50. In this tea plantation ecosystem, the soil food web gradually degraded alongside plantations. Compared with the large macro-aggregates, the structure of soil food web was relatively less disturbed in the micro-aggregates. Notably, the degradation of soil food web alongside plantations underscores the need for sustainable soil management practices that would maintain soil health in the hilly area of western Sichuan in China.





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