沙地榆树疏林草原地上植被与土壤线虫的关系及其对干扰的响应

As the intrazonal succession climax in semi-arid region, sandy Elm-sparse grassland plays a very important role in maintaining biodiversity, landscape construction and ecological function expression. In this study, three elm-sparse grasslands under disturbance including grazing, enclosure, enclosure plus reseeding measure are chosen. We mainly focus on species diversity, functional traits and functional groups, and the characteristics of soil nematode in community composition and their diversity. We analyze the dynamics between species diversity and soil nematode in horizontal distribution, and between soil nematode and soil properties in vertical distribution. We try to clarify their relationship and the effects of sparse Elm trees on their distribution pattern at community level. we quantified the attribute data and effectively integrated the sparse Elm with vertical heterogeneity and herb with horizontal heterogeneity into the whole ecosystem. Then we discuss the dynamical relationship between functional diversity and soil nematode, and their collaborative or divergent responses to different disturbance at ecosystem level. Our study not only make up the lack of functional diversity in above-ground and soil nematode in under-ground, but also effectively select sensitive plant species, functional traits, soil nematode types and functional groups. That would help us to judge the ecosystem development trend and provide scientific support for the ecosystem protection and management in the future.

沙地榆树疏林草原作为隐域性植被演替顶级群落，在半干旱风沙区物种多样性维持、景观构建和生态功能表达中具有重要作用。本项目选择放牧、围封、围封+补种三种干扰类型的沙地榆树疏林草原为对象，系统研究植物的物种多样性、功能性状和功能群多样性，以及土壤线虫群落组成和功能群团特征。通过物种多样性和土壤线虫在水平空间分布、土壤线虫与土壤理化性质在垂直空间分布变化研究，在群落层面上阐明地上植被与土壤线虫关系以及稀疏榆树对二者分布格局的影响。通过功能性状量化过程将具有垂直空间异质性的榆树和水平空间异质性的草本植物有效整合，在生态系统层面上讨论植物功能多样性和土壤线虫的变化关系、以及二者对干扰响应的协同性或差异性。本研究不仅弥补了沙地稀疏榆树草原地上植被-土壤线虫关系研究的缺失，而且能筛选出对干扰措施响应敏感的植物种和功能性状、土壤线虫种类和功能群团，为预测沙地榆树疏林草原的发展趋势和制定管理措施提供科学依据。

由于过度放牧导致沙地榆树疏林草原退化严重，为了能够维持该顶级群落的可持续发展，本项目采用围封、围封+补播的方式与放牧地进行对比分析，分析干扰后生态系统内植被的变化、土壤线虫的变化和土壤理化性质的变化。结果表明：短期围封对植被密度、盖度、高度和生物量等植被生长指标的促进作用显著，围封使榆树疏林草地植物群落Shannon-Wiener物种丰富度指数和FRic功能丰富度指数显著高于放牧样地。放牧、围封、围封+补播处理和土层差异均显著影响了土壤线虫总数、各营养类群的相对丰富度和多度、部分生态指数等。围封使得土壤线虫、植物种类和土壤理化性质的相关性增加，如铵态氮、土壤全磷和速效磷对线虫和植物种类的影响均较大。在现有的研究中，在放牧样地内可将黄蒿、虎尾草作为响应较敏感的植物种类；将具脊垫刃属、拟鞘属、峡咽属等线虫属作为指示生物。在围封样地中，把糙隐子草、马齿苋作为响应较敏感的植物种类；将拟丽突属和鹿角唇属作为该样地的指示线虫。通过该项目的研究，已确定围封可恢复沙地榆树疏林草原植被，同时显著影响土壤线虫和土壤理化性质，短期围封有利于区域内植被恢复。