青藏高原不同牧草人工草地对土壤线虫群落的影响

Abstract

为缓解草蓄矛盾，青藏高原人工草地得到快速发展。土壤线虫对环境变化敏感，是草地生态系统的重要组成部分。然而，不同牧草人工草地对土壤线虫群落的影响尚不明确。2016年7月，对多年生禾本科（垂穗披碱草Elymus nutans Griseb.、老芒麦Elymus sibiricus L.、早熟禾Poa annua L.和羊茅Festuca ovina L.）、一年生禾本科燕麦Avena sativa L.和多年生豆科紫花苜蓿Medicago sativa L.等6种单播牧草人工草地（建植期4年）和天然草地（对照）的土壤线虫群落进行了调查。结果表明：（1）土壤线虫隶属于2纲8目32科58属，平均密度为1754个/100 g干土；紫花苜蓿样地的线虫密度最低，为949个/100 g干土；燕麦样地最高，为3267个/100 g干土；（2）与天然草地相比，燕麦样地的线虫群落总密度、多样性以及植食性和杂食-捕食性线虫密度显著增加，而其他人工草地的线虫群落密度、多样性以及植食性、食真菌和食细菌线虫密度均无显著变化；（3）土壤线虫总密度以及各营养类群密度在不同人工草地间差异显著，且均在燕麦样地最高；（4）建植人工草地改变了土壤线虫的群落组成，冗余分析（RDA）表明土壤全钾、碳氮比、全磷和有效钾是影响线虫群落组成的重要因子。研究表明青藏高原建植人工草地通过改变植物群落和土壤理化性质对土壤线虫群落产生影响，其中种植燕麦短期内可显著提高土壤线虫群落的密度和多样性。青藏高原生态环境脆弱，在大面积建植人工草地前应对地下生态过程进一步深入研究。;Artificial grassland with higher productivity has developed rapidly in recent years in order to balance available pasture and stocking rates on the Qinghai-Tibetan Plateau. Soil nematodes are sensitive to environmental changes, which are important components of grassland ecosystems. However, little is known about the effects of the artificial grasslands with the different forage species on the diversity of soil nematode communities. Soil nematode communities in the natural grasslands (control) and artificial grasslands were investigated in July 2016. Four perennial grass (Elymus nutans Griseb., Elymus sibiricus L., Poa annua L., and Festuca ovina L.), one annual grass (Avena sativa L.), and one perennial legume (Medicago sativa L.) were selected. Forages were grown for four years in monoculture in this study. Soil nematodes were extracted from 50 g of fresh soil using Baermann funnels for each composite soil sample. The composite samples were comprised of three soil cores taken from the upper 0-15 cm soil. Soil nematodes were identified into 2 classes,8 orders,32 families,and 58 genera. The results showed that:(1) the average nematodes abundance was 1754 ind./100 g dry soil, ranging from 949 ind./100 g dry soil in the M. sativa to 3267 ind./100 g dry soil in the A. sativa. (2) The total abundances, taxonomic richness, Shannon diversity index of the soil nematodes communities, and the abundances of herbivores and omnivores-predators were significantly higher in the A. sativa grasslands compared to the natural grasslands. However, no significant difference was observed in the total abundances and diversity of the nematode communities and the abundances of fungivores, bacterivores and omnivores-predators between the rest artificial grasslands and natural grasslands. (3) The abundances of the soil nematode communities and each trophic group differed significantly among the different artificial grasslands, with the maximum values occurring in the A. sativa grasslands. (4) Redundancy analysis results showed that soil total K, C/N, total P and available K were the important factors affecting the composition of the soil nematode communities. The results suggested that establishing artificial grasslands with changes in plant communities and soil physico-chemical properties led to the change of soil nematode communities on the Qinghai-Tibetan Plateau, and the abundances and diversity of soil nematode communities were significantly increased by planting A. sativa. Given the vulnerability of ecological environment on the Qinghai-Tibetan Plateau, the changes in soil nematode communities depicted here indicate that underground process should be further studied before the area of artificial grasslands has been greatly increased.