氮添加对贝加尔针茅草原土壤线虫群落特征的影响

摘要

The community characteristics of soil nematodes in a Stipa baicalensis steppe in Inner Mongolia under different nitrogen treatments (0,15,30,50,100,150,200,300 kg N hm-2 a-1) were studied by field investigation and sample analysis using the morphological classification method.In total,52 genera were identified in all the samples.The dominant species were Helicotylenchus,Acrobeles,and Aphelenchus.Soil nematodes showed an obvious surface convergence phenomenon,and their relative density was not significant.Based on the functional groups,the addition of Bacterivores nematodes and Predators/Omnivores showed a negative correlation with the increase in nitrogen application level.The ecological indices such as abundance (SR),diversity (H'),and evenness (J') of soil nematodes increased with the increase in nitrogen application level,reaching their maximum values at N50.In all treatments,the pathway index was less than 0.75,indicating that fungi decomposed organic matter in the soil.The ecological indicators showed that nitrogen application at ＜ N50 can improve the soil environmental condition and reduce the effects of plant parasites on plant communities and productivity.When the amount of nitrogen applied was ＞N100,the soil pH value decreased significantly,the nitrate nitrogen and ammonium nitrogen contents increased significantly,the soil life history k countermeasures were significantly reduced,and r countermeasures were significantly increased,significantly altering the soil nematode community structure.%以内蒙古贝加尔针茅草原为研究对象,通过氮素添加(0、15、30、50、100、150、200、300 kg N hm-2 a-1)模拟氮沉降的控制实验,研究氮沉降对内蒙古贝加尔针茅草原土壤线虫的群落结构和多样性的影响.结果表明,在本实验所有样品中共鉴定出52个属,优势类群为螺旋属(Helicotylenchus)、丽突属(Acrobeles)和真滑刃属(Aphelenchus).土壤线虫具有明显的表聚现象,相对密度变化不显著.从功能类群上看,随着氮素添加水平的增加,食细菌类群(Bacterivores)线虫和捕食类群/杂食类群(Predators/Omnivores)线虫氮素添加水平均成负相关.从生态指标来看,在＜N50施氮范围内对土壤线虫的丰富度(SR)、多样性(H')、均匀度(J')等生态指标有促进作用;通路指数在试验的所有处理中都小于0.75,表明土壤中的有机质分解途径是以真菌为主;瓦斯乐思卡指数表明,少量施氮可以改善土壤的环境状况,减少植物寄生类群(Plant parasites)线虫对植物群落及生产力的影响.当施氮量＞N100时,土壤pH值显著降低,硝态氮和铵态氮显著增加,土壤中生活史k对策者的线虫显著减少,r对策者显著增加,世代交替加快,土壤线虫群落结构显著变化.