【作者】 支德娟；

【导师】 李红玉；

【作者基本信息】 兰州大学 ， 生物化学与分子生物学， 2009， 博士

【摘要】 本文对沙坡头人工固沙区不同结皮、不同固沙年限、灌区与非灌区、不同固沙植物的线虫群落特征以及沙坡头人工固沙区线虫营养类群的空间异质性分布进行了研究,最后以红卫天然固沙区为参考点,对土壤线虫群落的演变趋势进行了探讨。本文的研究目的在于评价沙坡头土壤线虫群落对其栖居环境的指示作用,为继续加强固定沙丘的管理、保护和监测提供科学依据。结果表明:在沙坡人工固沙区,土壤线虫呈明显的表聚集,其主要食物源为微生物,且通常以细菌降解通路占优势,偶见以真菌降解通道占优势,如在秋季藻类结皮和藓类结皮的部分土壤样品。植食性线虫尤其是Rotylenchus在降雨后成为优势属。在沙坡头人工固沙区不同类型的结皮中,捕食者百分比、线虫数量,所鉴定的线虫属数和成熟度指数随结皮的发育而增高。主要响应曲线(PRC)揭示了土壤线虫群落沿早期结皮包括流动沙丘在内的物理结皮和藻类结皮向晚期结皮苔藓结皮演替的环境梯度发育,线虫群落的发育与生物结皮的发育平行。随着沙丘的固定,线虫丰度,食真菌线虫、杂食性线虫和捕食性线虫的百分比、成熟度指数、香农指数、均匀度指数和结构指数受沙丘固定年限的影响,这些指标同土壤物理化学性质呈不同程度的相关。冗余分析(RDA)显示了两个明显的环境梯度:沙丘的固定初始和沙丘固定的早晚。沙丘的初始固定效应可以由人工植被的输入得到解释;而沙丘固定的早晚效应则由维管束植物和隐花植物的演替以及固定沙丘土壤物理化学性质的不断变化得到解释。沙坡头人工固沙区的灌区与非灌区,线虫总数、植食性和杂食性线虫相对丰度、cp类群和多样性指标受有无植被输入或有无灌溉添加的不同程度的影响;主成分分析(PCA)得到了沿第一轴有无植被输入的环境梯度和沿第二轴有无灌溉添加的环境梯度。土壤线虫可以指示沙丘固定方法,即有无人工植被输入和灌溉添加与否。聚类分析结果按照植被输入的有无将线虫群落划分为二个主要的类群。这表明植被的输入比灌溉添加对线虫群落发育更为重要。在沙坡头26龄和51龄人工固沙区,线虫总数和各营养类群空间异质性分布特征为上层土壤(0-10cm)强于下层土壤(10-20cm)。除植食者外,较晚固定沙丘线虫总数和营养类群的空间异质性高于较早固定的沙丘。线虫群落本身内在的固有性质和植被的介导作用是导致土壤线虫空间分布格局的原因。人工固沙植物的种类和功能类群分别介导了其下土壤线虫群落的差异。与浅根系的油蒿相比,深根系的柠条和花棒下0-10cm土层线虫的Fu和Fu%,Pr,线虫通路比值,多样性指标存在显著差异:不同种类的人工固沙植物引起其下的土壤线虫群落在0-10cm土层线虫的营养类群多样性不同,10-20cm土层各线虫属线虫的数量、线虫分类单元总数、P1、Om和丰富度指数在柠条和油蒿之间存在显著差异。固沙植物的功能类群比其种类的不同在某种程度上对线虫群落有更大的影响。沙坡头人工固沙区在0-10cm土壤深度,随着固沙年限的延长,栖居其下的土壤线虫群落有与红卫天然固沙参考点有趋同的倾向,而在10-20cm土壤深度,沙坡头人工固沙区土壤线虫群落与红卫天然固沙参考点的土壤线虫群落相差很大。结皮的盖度、植被的组成和土壤物理化学性质的恢复状态是解释沙坡头人工固沙区土壤线虫群落趋同存异的因素。由于固定沙丘仍然尚处于其早期发育阶段,成熟度指数的敏感度不足以显示土壤环境变化。或者说,土壤环境的差异在成熟度指数的检测限以下。成熟度指数仅在春季采集的土壤样品中藓类结皮显著高于藻类结皮;较晚固定的沙丘和较早固定的沙丘间相比差异不显著;在灌区和非灌区也不受灌溉或植被输入的影响,它在本研究体系中不是一个灵敏的指标。结构指数同时考虑了线虫营养类群和生活史,这一指数随固定沙丘年限的延长而显著升高。在评价沙丘固定年限过程中比成熟度指数灵敏,它可以有效地指示固定沙丘的演替。PRC,RDA,PCA和聚类分析在分析土壤线虫群落对不同类型的结皮、不同年限的固定沙丘、灌区与非灌区人工固定沙丘中的响应时,它们给出了满意的结果。以线虫群落的种属组成为数据基础的群落分类与排序方法是反映沙坡头人工固沙区线虫群落对其栖居环境变化的灵敏方法。更多还原

【Abstract】 The characteristics of nematode communities and their composition were investigated under various crusts, in artificial vegetation belt with or without irrigation, along an age sequence after sand dunes stabilized, under assisted re-vegetation plant of Caragana korshinskii Kom., Hedysarum scoparium Fisch. and Artemisia ordosica Krasch. at Shapotou in the Tengger Desert. In contrast to native vegetation sites at Hongwei, evolution characteristics of the nematode communities were also investigated. Additionally, spatial distribution of nematode trophic groups was also studied in stabilized sand dunes at early and late stage. The objective is to evaluate whether nematodes could be as an indicator of their inhabitats during ecological reclaimation after sand dunes stabilized at Shapotou.Our results showed that soil nematodes distributed mainly at the upper soil layer in sand dunes at Shapotou, and bacterivores and fungivores were dominant in our system, indicating that the principal food source for nematodes was microbial. Especially, bacterivores were predominant in most observed sites, it suggested decomposition processes in our system were often bacterial based energy channel, occasionally fungal based channel in algal crusts and moss crusts in autumn, althougy they were dependent ultimately on the plants. In addition, plant feeders i.e. Rotylenchus could get dominant after rainfall.The abundance of nematodes (N), the proportion of predators, maturity index (MI), the number of nematode taxa identified (S) and Shannon index (H’) were affected significantly by crust type. Bare soil, physical soil crusts, algal crusts and moss crusts also were comprised of differing community composition as indicated by principal response curves (PRC) analysis. These results indicate that nematode communities develop parallel to crust development during the assisted re-vegetation of migrating sand dunes.N, the proportion of fungivores, omnivores and predator, MI, H’, evenness and structure index were affected significantly by the age of stabilized sand dunes, and were correlated with soil physical and chemical properties on different degrees. There were differences on N, the proportion of fungivores, H’ and evenness between the shifting dunes and the stabilized dunes, but not within the different succession stages of the stabilized dunes. The result of redundancy analysis (RDA) using data on nematode community composition showed that shifting sand dunes were clearly separated from stabilized sand dunes, and younger sand dunes stabilized for 16 years and 26 years were also separated from older dunes stabilized for 43 years and 51 years to a lesser degree. Those results indicated that changes on nematode communities could predict the initial sand dune stabilization due to the planting of artificial vegetation, and clearly differentiate sand dune succession accompanied by the vegetation succession and the variation of soil properties.In bare soil between vegetation and soil under the vegetation in Shapotou, N, the relative abundance of plant feeders, S, species richness (SR) and cp groups responded to vegetation. The relative abundance of omnivores, S, H’, dominance, SR, cp3-5 were significantly affected by irrigation supplements. Principal component analysis (PCA) revealed that a vegetation gradient from bare soil between vegetation to soil under vegetation along the first axis, while an irrigation gradient along the second axis. Similarly, classification analysis based on all cased involved indicated that two-main group of nematodes was distinguished by their habitats under vegetation from bare soil. Those results suggested that vegetation input might play a more important role on nematode community composition than irrigation supplements for stabilization of shifting sand dunes.The abundance of nematode and trophic groups aggregated stronger in depth of 0-10 cm than that in depth of 10-20 cm in sand dune stabilized for 26 years and 51 years. Nematode communities were more spatial heterogenous in late than in early successional sand dunes since stabilization except plant feeders. The spatial heterogenous distribution patterns can be explained by the intrinsic nematode population process and mediated by vegetation patterns.Assisted re-vegetation plant species and function groups affect nematode communities. The abundance of fungivores and predators, relative abundance of fungivores, nematode channel ratio and diversity index diffentiated significantly between shallow rooted shrub of Artemisia ordosica and deep rooted shrub of Caragana korshinskii and Hedysarum scoparium at 0-10 cm soil depth. The plant species induced trophic diversity different significantly at upper soil layer, and the abundance of nematode genera, plant feeders, omnivores, S and SR at lower soil layer. Assisted re-vegetation plant function groups may play a more important role than plant species.Nematode communities along dune age at 0-10 cm soil depth in Shapotou region developed towards the level of a reference site of Hongwei native vegetation region. However, nematode communities at 10-20 cm soil depth differentiated significantly between those two region. Those could be due to crust coverage, plant vegetation and the reclamation status of soil physical and chemical characteristics.MI was only higher significantly under moss crusts than beneath algal crusts in April, it was affected by age for sand dune stabilization, irrigation and plant input. MI may be a poor indicator of changes in nematode communities under various inhabitat in our system. Whereas structure index increased significantly with dune age and it could act as robust indicators of stabilized sand dune succession. Multivariate methods of PRC, RDA, PCA and classtification analysis could be discriminatory for subtle differences, and these methods are sensitive to respond changes in nematode inhabitat conditions in Shapotou.更多还原