中文摘要：

为探究半干旱区湿地-干草原生态交错带的边界及影响其植被空间分布格局的主要环境因子,以宁夏哈巴湖荒漠湿地自然保护区内的四儿滩湿地为例,采用样线调查法获得植被与环境数据：首先利用游动分割窗技术对研究区进行交错带定量判定,将其分为旱生带、交错带、湿生带并计算沿不同生境梯度β多样性变化趋势;然后,采用典范对应分析法对研究区植被数据矩阵和环境数据矩阵进行排序,同时进行排序轴与土壤环境因子间的秩相关分析。结果表明：采用游动分割窗技术判定四儿滩湿地-干草原交错带最适窗口宽度为6~8个样方;不同生境带β多样性指数存在明显梯度变化;典范对应分析结果显示,植被在CCA排序图上的分布与游动分割窗技术的划分结果相吻合,含盐量（质量分数）、含水量是影响四儿滩植被空间分布的主要环境因子,对含盐量和含水量有较高适应值的物种集中分布于土壤盐渍化严重的湿生带。研究结果将为四儿滩湿地的恢复和保护提供参考。

英文摘要：

[Background] Siertan Wetland is the largest wetland of Habahu Desert Wetland Nature Reserve in Yanchi County,Ningxia Autonomous Region. Through the annual vegetation investigation which has been carried out for 11 years,we found that the area of Siertan Wetland is shrinking year by year. Many researchers concluded that the ecotone is very sensitive to the change of environment,thus it can be used to predict the change of the ecological environment in advance. This study is to quantitatively determine the ecological ecotone boundary and the main environmental factors that affect the spatial distribution pattern of the species. [Methods] Firstly we used moving split-window technique to quantitatively determine the ecological ecotone. Use of the moving split-window technique required that：we chose an appropriate even number of representative samples as a whole window,then divided the whole window in half and calculated their dissimilarity coefficient. We continuously moved the window right to the next sampling point and repeated the operation above again,until the right window reached the final sampling points. We then draw a scatter diagram of the dissimilarity coefficient changes by quadrats. Further,according to the result of determination we divided the research area into wetland regions,ecotone and arid region,and analyzed characteristics of beta diversity in the three different habitats of the four different sample lines. Finally,Canonical Correspondence Analysis（ CCA） was used to determine which environmental factors contributed most to the distribution of the vegetation. [Results]The results showed that ecotone was determined clearly by moving split-window technique under 6- 8quadrats,the optimal window width of east transect line was 6 quadrates,the optimal window width of west,south and north transect line was 8 quadrates. Beta diversity index showed significant differences in different habitats. The result of CCA indicated that the total salt content and moisture content were the main environmental