宁南山区不同植被恢复方式下土壤线虫群落特征:形态学鉴定与高通量测序法比较

线虫是土壤食物网的重要组分, 也是土壤健康与生态系统恢复的重要指示生物, 因此准确测定线虫群落特征是发挥其生态指示作用的基础。传统线虫学研究多采用形态学鉴定方法, 但高通量测序技术近年来也逐渐受到重视。然而, 关于这两种方法的对比研究目前仍比较缺乏。本研究同时采用形态学鉴定和高通量测序法, 在黄土高原宁夏南部山区, 对不同植被恢复方式下(农田、自然恢复草地、柠条(Caragana korshinskii)人工林地和苜蓿人工草地)土壤线虫的数量、群落格局和生态指数进行了测定和比较。结果表明: (1)高通量测序仅能提供线虫类群的相对多度, 而形态学鉴定法能够测定土壤线虫的绝对多度, 后者测定结果表明3种植被恢复样地, 特别是自然恢复草地和柠条人工林地, 较农田具有更高的土壤线虫多度; (2)高通量测序法检获的线虫类群数(3纲4目26科42属)高于形态学鉴定法的测定结果(2纲3目18科27属), 但两种方法仅检获15个共有线虫属, 前者检测到的植物寄生线虫属数(22属)较后者(7属)显著增加, 而食细菌线虫和杂食-捕食线虫则相反; (3)在两种方法下, 相比农田, 3种植被恢复样地尤其是自然恢复草地和柠条人工林地, 其食微线虫的相对多度均显著下降, 而植物寄生线虫和杂食-捕食线虫的相对多度大幅上升, 这也导致线虫成熟度指数(MI)和植物寄生线虫指数(PPI)的提高及瓦斯乐卡指数(WI)的显著下降; (4)相比形态学鉴定法, 高通量测序法能检测到更丰富多样的植物寄生线虫, 在该方法下土壤线虫群落的组成、结构和生态指数在植被恢复样地与农田之间的差异也更为显著。综上所述, 采用形态学鉴定和高通量测序法测定的不同植被恢复方式下的线虫群落特征具有显著差异。

Characteristics of soil nematode community under different vegetation restoration approaches in the mountainous region of southern Ningxia: A comparative study based on morphological identification and high-throughput sequencing methods

Aims Nematodes are considered as an important part of the soil food web, and their community characteristics are an effective indicator of soil health and ecosystem restoration. The accurate measurement of soil nematode communities is necessary to better understand their ecological function. Historically, comparisons in nematode morphology has been used to understand nematode community characteristics. In recent years, the use of high-throughput sequencing (HTS) methods has become more popular. However, relatively little is known about how these two methods compare when analyzing soil nematode communities. Methods Here, we used morphological identification and HTS methods to simultaneously analyze soil nematode abundance, community composition and structure, and ecological indexes, under different vegetation restoration approaches (cropland, naturally restored grassland, Caragana korshinskiiplantation and Medicago sativaartificial grassland) in the mountain area of southern Ningxia in the Loess Plateau region. Result We found that morphological identification is a more accurate method to determine the absolute abundance of soil nematodes, while HTS can only obtain relative abundance data. In our study, the morphological method showed higher abundance of soil nematodes in the sites under vegetation restoration, especially in the naturally restored grassland and C. korshinskiiplantation. The HTS method, on the other hand, detected more nematode genera (42 genera belonging to 3 classes, 4 orders, and 26 families) than morphological method (27 genera belonging to 2 classes, 3 orders, and 18 families). However, only 15 genera were simultaneously identified with both methods, because the HTS method detected more plant-parasitic nematode genera (22) but fewer genera of bacterial-feeding nematodes and omnivores-predators than the morphological method. One major result indicated by both methods showed that the relative abundance of microbial-feeding nematodes greatly decreased, while those of plant parasites and omnivores-predators substantially increased, in all the sites under vegetation restoration when compared with nematodes in the farmland. This was especially the case in the naturally restored grassland and C. korshinskiiplantation, accompanied with the increases of maturity index (MI) and plant-parasitic index (PPI) and a decrease in the Wasilewska index (WI). When compared with the morphological method, the HTS method could detect more abundant and diverse plant parasites. Therefore, more significant differences were found in the composition, structure and ecological indexes of soil nematode communities when the HTS method was applied. Conclusion Overall, the characteristics of soil nematode communities and their response patterns to vegetation restoration highly depended on the applied methodology, which greatly influences the understanding and evaluation of how vegetation restoration impacts the soil ecosystem.