不同水分条件天鹅湖高寒湿地土壤线虫群落结构对氮沉降的响应

Response of soil nematode community structure to nitrogen deposition in the alpine wetland of Swan Lake under different water conditions

为探究氮沉降对干旱区高寒湿地土壤线虫群落结构的影响,本研究以天山中部的巴音布鲁克天鹅湖高寒湿地为样地,选取2个不同水分条件区域,分别喷施3个不同浓度氮素,开展野外原位模拟氮沉降控制试验,研究不同水分条件土壤线虫群落结构对氮沉降的响应。结果表明:地表季节性积水条件土壤线虫群落的优势属主要为前矛线属(Prodorylamus,29.30%),地表常年干燥条件土壤线虫群落的优势属是前矛线属(Prodorylamus,18.69%)、Laimydorus(20.21%)和螺旋属(Helicotylenchus,33.48%);在土壤水分和氮添加的共同作用下,杂食/捕食类线虫(OP)和食真菌类线虫(FU)丰度升高,植物寄生类线虫(PP)丰度降低;地表常年干燥条件下,氮添加对土壤线虫群落各生态指数影响不显著。在地表季节性积水条件下,随着氮添加浓度上升,富集指数(EI)和成熟度指数(PPI)先下降后上升,但氮添加对土壤线虫群落香农威尔指数(H)和优势度指数(λ)无显著影响,20 kg·hm^(-2)·a^(-1)氮添加会促进干旱区高寒湿地土壤有机质分解途径由细菌向真菌分解途径发展。土壤含水量、土壤电导率和碱解氮是影响土壤线虫群落结构的主要因素。研究表明,氮沉降增加会影响土壤线虫群落中不同营养类群的丰度,但对土壤线虫群落结构多样性和干旱区高寒湿地土壤生态系统稳定性影响较小。

The effect of nitrogen deposition on soil nematode community structure in an arid alpine wetland was determined in this study.The Bayanbulak Swan Lake alpine wetland in central Tianshan Mountains was taken as the sample site.Two areas with different water conditions were sprayed with three different concentrations of nitrogen.The response of soil nematode community structure to nitrogen deposition in the different water conditions was studied by in-situ simulated nitrogen deposition control experiments.Prodorylamus(29.30%)was the dominant genus of the soil nematode community under seasonal surface water conditions.The dominant nematodes in perennial dry soil were Prodorylamus(18.69%),Laimydorus(20.21%),and Helicotylenchus(33.48%).Under the combined effect of soil water and nitrogen,the abundance of omnivorous/predatory nematodes(OP)and fungivorous nematodes(FU)increased,while the abundance of plant parasitic nematodes(PP)decreased.In perennial dry soil,nitrogen deposition did not significantly affect these ecological indices in soil nematode communities.Under seasonal surface waterlogged conditions,the enrichment(EI)and maturity(PPI)indices initially decreased then increased with increasing nitrogen concentration.However,nitrogen addition had no significant effect on the shannon index(H)and dominance(λ)indices in soil nematode communities.It was observed that addition of 20 kg·hm^(-2)·a^(-1)nitrogen promoted the development of the organic matter decomposition pathway by bacteria and fungi in the alpine wetland soil of the arid area.Soil water content,soil conductivity,and alkali-hydrolyzed nitrogen were the main factors affecting soil nematode community structure.The findings indicate that increased nitrogen deposition can affect the abundance of different trophic groups in soil nematode communities but has little impact on the structural diversity of soil nematode communities and stability of the alpine wetland ecosystem in arid areas.