不同施氮玉米田土壤线虫群落特征及对土壤质量的指示作用

Indicative Effect of Soil Nematode Community Characteristics on Soil Quality in Maize Field Under Nitrogen Application

在甘肃省玉米生产中存在长期过量施用氮肥的问题,导致农产品品质下降、地下水污染、耕地土壤质量退化等问题,土壤线虫作为指示生物能在一定程度上反映出土壤生态系统的质量状况。在甘肃省榆中县玉米田进行了0(CK)、5、10、15 g N/(m^(2)·a)4个不同施氮水平的处理,分析了各处理对土壤线虫群落的多度、属丰富度、成熟度指数、富集指数、结构指数等生态指数及复合代谢足迹的影响。采用非度量多维尺度法分析了土壤线虫的群落组成情况,并采用置换多元方差分析检验了不同施氮处理间土壤线虫群落组成的差异。结果表明,适量施氮使线虫的总多度、食细菌线虫和植食线虫的多度显著增加,使食真菌线虫和杂食捕食线虫多度显著减少,进而导致线虫群落的组成发生了显著性变化,同时也使线虫群落的属丰富度显著降低。此外,随着施氮水平的逐渐增加,线虫的体型呈逐渐减小趋势,基础指数显著升高,结构指数、成熟度指数、复合代谢足迹显著降低,反映出施氮后线虫群落逐渐不稳定,施氮导致土壤食物网的连通性降低、食物链变短,食物网分解途径由以真菌途径为主转变为以细菌途径为主,食物网能量流动总体变慢。

In the practise of maize cultivation in Gansu province,long-term excessive application of nitrogen fertilizer causes the degradation of soil quality and some other problems.Soil nematodes,an indicator organism,can reflect the status of soil ecosystem.In this study,three nitrogen treatments(5、10、15 g N/(m^(2)·a)and 0 g N/(m^(2)·a)ascontrol treatments(CK)were gathered from in the maize planting field of Yuzhong county,Gansu province.The effects of each treatment on the ecological indexes and metabolic footprints of soil nematode community,such as abundance,richness,maturity index,enrichment index and structure index,were analyzed.The community composition of soil nematodes was investigated by non-metric multidimensional scale analysis,and the differences of community composition among different treatments were tested by Permutational multivariate analysis of variance.The results demonstrated that nitrogen application significantly increased the total abundance of nematodes,bacteria-eating nematodes and herbivorous nematodes,and significantly decreased the abundance of fungus-eating nematodes and omnivorous nematodes,leading to an obviously change in the composition of nematode community,and significantly reduced the genus richness of nematode community.In addition,with the increase of nitrogen application concentration,the body size of nematodes decreased gradually,the basal index increased significantly,and the structure index,maturity index and metabolic footprint decreased significantly.The results showed that the nematode community became unstable after nitrogen application,the connectivity of soil food web was reduced and the food chain was shortened due to fertilization,the decomposition pathway of food web was changed from fungal pathway to bacterial pathway,and the overall energy flow of food web was slowed down.