天然富硒区广西壮族自治区桂平市水稻土壤线虫群落结构特征及其指示意义

Selenium is one of the essential trace elements for humans. Adequate intake of Se may reduce the body risk of some types of cancer and protect the liver and resist oxidation. Agricultural products are the main source of selenium for the human. Therefore, the development of selenium-rich agriculture is of great significance to improving human health. However, no research on ecological security assessment in selenium-rich soils has been carried out yet. Soil organisms are the primary regulators of the soil material cycle and energy flow process. Soil fauna has been gradually used in soil environmental quality monitoring with widespread attention to the diversity of soil fauna and its ecological importance. Nematode is the most abundant metazoan in soil, and its community structure and diversity indicate energy flow and environmental quality in soil ecosystem. In this study, natural Se-rich paddy soils (100-900 μg/kg Se) in Guiping City, Guangxi Zhuang Autonomous Region were classified into three groups (low Se group, medium Se group and high Se group) for nematode communities analysis. Non-metric multidimensional scaling ordination of nematode community showed that soil nematode community structure in different groups was significantly different. A total of 31 genera of nematodes were found in all the samples, and the sensitive nematode genera (Acrobeloides, Filenchus, etc.) exhibited different distribution among the different groups. Compared with the low Se group, the density of nematodes in medium Se group and high Se group increased while the relative abundance of cp-2 nematodes, the relative abundance of fungivores, the F/B value and structural index SI decreased significantly. Correlation analysis showed that nematode density, the relative abundance of Chronogaster and Prismatolainus increased with the increase of soil Se contents, while the relative abundance of Acrobeloides, the relative abundance of fungivores, F/B value and SI decreased. In conclusion, selenium increased nematode density but simplified soil food web with inhibited sensitive genera. Our study primarily demonstrated that a high soil selenium level might bring a negative effect on nematode community in paddy soil. It is necessary to regulate soil selenium levels to protect soil biodiversity when utilizing natural selenium-rich soil or fertilizers to produce selenium-rich agricultural products. Additionally, considering the sensitive response to selenium, nematode could be used as a bioindicator for natural selenium-rich paddy soil management. This study provides a reference for the scientific evaluation of ecological security of natural selenium-rich paddy soil. For further research in the indication of nematodes on soil selenium, biological and abiotic factors of the soil should be taken into account in this system.