“土岛”对荒漠草原植被恢复的作用与机理研究

By wind erosion and desertification, "soil islands" which are fragmented habitat with the features of sierozem and its parent material have became the reserved area of zonal plants, species provenance and reference of vegetation recovery in desertified steppe. Therefore seeking the ecological value of soil islands has a great significance to the bio-diversity protection and the ecological restoration in this region. In order to evaluate the similarity of plant and seek a similar gradient sequence on the scale of soil island by the index of Jaccard, we will conduct a research that plant and abiotic factors will be investigated in large sample size on the typical areas distributing many soil islands. Taking the survey of line transect with geostatistics method we will study the spatial heterogeneity of plant and abiotic factors on single soil island which belong to different scales confirming the dominant affecting factors of zonal plant and the its diffusion ability based on redundancy analysis. And then the cumulative function of water and nutrient in soil-plant system and the suitability of combinating of zonal plant and soil island will be evaluated based on the field investigation and the method of stepwise for different patches of single excellent population such as Stipa brievflora, Agropyron mongolicum and Lespedeza potaninii. At last , the ecological value and the effect in vegetation restoration of soil island will be assessed in desertified steppe by the combinating the characteristic and spatial variability of the patches for single excellent plant and the feature of plant community in different soil islands

由于风蚀沙化，残留在荒漠草原的灰钙土或其母质片断化生境- - 土岛- - 成为地带性植物保留地、植被恢复的种源地和参照系统，挖掘其生态价值对于本区生物多样性保护和生态恢复具有重大意义。本项目选择土岛分布较多的典型区域，通过大样本量土岛植物和环境因子调查，运用Jaccard指数评价土岛的植物相似性，建立不同尺度等级的土岛序列；采用样线调查结合统计学和地统计学方法，研究不同尺度等级中单个土岛的植物和环境因子空间异质性，并用冗余分析确定影响地带性植物种的主要环境因子及其扩散性能；进而针对针茅、沙芦草、牛枝子等单优种群斑块，运用野外观测法和逐步回归法，评价其植物-土壤系统的水分和养分蓄积功能，探讨地带性植物与土岛结合的适宜性；最后将单优植物斑块的特性、空间异质性与大小不同土岛的植物群落特点结合，评价土岛的生态价值及其在荒漠草原植被恢复中的作用。

由于风蚀沙化，残留在荒漠草原的灰钙土和沉积母质型片断化生境——土岛成为地带性植物保留地、植被恢复的种源地和参照系统，挖掘其生态价值对于本区的生物多样性保护和生态恢复具有重大意义。本项目选择土岛分布较多的典型区域，通过大样本量土岛植物和环境因子调查、Pleiades1A卫星影像解译和形状特征测量，研究了土岛特征及其成因；利用无人机、空间抽样技术等，选择具有大、中、小土岛的3个重复开展土岛特征的详细调查和长期监测，研究土岛与周边沙化土地的水分、土壤、植被差异及其影响因子，典型地带性植物扩散作用；通过原位试验和采样分析，研究以针茅为代表的土岛上地带性植物的养分积聚功能。研究发现，（1）黄土地貌和风沙地貌交错带的土岛是一个水蚀切开地表、风蚀全过程主导、崩塌和人类活动（牲畜踩踏）促进的多因素作用结果，风蚀是主要成因。（2）土岛与外围的土壤呈现明显的土-沙二元结构。主要体现在质地、紧实度和水分等物理特征方面。（3）土岛内部与外部沙化土地均显示原生针茅群落与沙生猪毛蒿群落明显空间分异，两者互相作用的机率较小；随着土岛面积的逐渐减小，土岛界面与沙地界面的作用机率增加。多元统计分析结果表明：土壤粒径、土壤有机碳、土壤含水量能够很好的解释土岛内外植物多样性的差异。（4）土岛内针茅个体的扩散首先表现为中心针茅个体的退化或老化，随后呈现跳跃式扩散方式。变差分解结果表明，环境过滤和扩散限制共同调控土岛群落物种组成。（5）老年较大针茅丛具有降低根系空间pH和CaCO3含量的作用。在实际工作中要加意保护面积大于200m2以上、草原植被结构良好的土岛。