天然高寒草地转变为燕麦人工草地对土壤线虫群落的影响

为查明高寒草地上种植燕麦(Avena sativa)对土壤线虫群落的影响,于2014年7、9月用土钻法和湿漏斗法(Baermann法)对西南民族大学青藏高原畜牧业高科技研发示范基地内燕麦地(Oat grassland,OG)和天然草地(Natural grassland,NG)的土壤线虫群落进行调查。共分离土壤线虫10179条,隶属于2纲8目50科143属,平均密度477条/100g干土。燕麦地与天然草地土壤线虫群落结构具有明显差异,影响群落结构的主要类群为拟丽突属(Acrobeloides)、原杆属(Protorhabditis)、丝尾垫刃属(Filenchus)和盘旋属(Rotylenchus),但不同月份间存在差异。燕麦地的土壤线虫群落密度、食细菌线虫密度、食真菌线虫密度和自由生活线虫成熟度指数(MI)均显著高于天然草地(P0.01;P0.05;P0.001;P0.01),植物寄生线虫成熟度指数(PPI)则显著低于天然草地(P0.05)。两种草地7月份的土壤线虫群落类群数和香农多样性指数(H′)均显著低于9月(P0.05),仅燕麦地7月份的食细菌、食真菌线虫密度和Simpson优势度指数(C)显著高于9月(P0.05;P0.001;P0.01)。典范对应分析(Canonical correspondence analysis,CCA)及回归分析结果表明,土壤pH、有机质、全氮、速效磷和含水量是影响线虫群落的主要环境因子。研究结果表明,高寒草地种植燕麦后在短期内改变了线虫群落结构,增加了线虫群落密度以及食细菌和食真菌线虫在群落中的比例,以植物寄生线虫为主的群落营养结构转变为以食细菌线虫为主,同时也增加了线虫群落不同月份间的差异。

Effects of the transformation from natural alpine grassland to artificial oat grassland on the soil nematode communities

The aim of this study is to disentangle the effects of planting artificial oat grassland in the natural alpine grassland on soil nematode communities on Qinghai-Tibetan Plateau. Investigations were respectively performed on the soil nematode communities in an oat grassland (OG) cultivated for two years and a natural grassland (NG) in Hongyuan County, northwest Sichuan, in July and September 2014. Soil nematodes were extracted from soil samples using Baermann method in the laboratory. A total of 10179 soil nematodes were extracted and affiliated with 2 classes, 8 orders, 50 families, and 143 genera. The community abundance was 477 individuals 100 g^-1 dry soil. The taxonomic composition of the soil nematode communities in OG differed from those in NG driven by the determining genera of Acrobeloides, Protorhabditis, Filenchus and Rotylenchus. The abundance of nematode communities, functional groups of bacterivores and fungivores, the maturity index (MI) were significantly higher in OG than those in NG (P<0.01; P<0.05; P<0.001; P<0.01), whereas an opposite pattern was observed for the plant parasitic index (PPI) (P<0.05). Taxonomic richness and Shannon-Weiner index were both strongly enriched in September for OG and NG, compared to those in July (P<0.05). However, a higher Simpson index and larger abundance of bacterivores and fungivores were observed in July (P<0.05; P<0.001; P<0.01) for OG. The results of canonical correspondence (CCA) analysis and multiple regression analysis showed that soil characteristics (pH, soil organic matter, total N, available soil P and soil water content) exerted an overriding influence on the soil nematode communities. Overall, the study indicated that the transformation from natural alpine grassland into artificial oat grassland led to an enrichment in the overall soil nematode community abundance and a clear variation in the community structure. Specifically, the relative abundances of the bacterivores and fungivores increased, and the trophic structure was dominated by bacterivores rather than plant-parasites. In addition, the temporal stability of soil nematode communities decreased along the transformation.