中文摘要：

植被空间分布格局深受环境影响。分析植被与环境之间的关系一直是植物生态学的中心问题，论文从黄土高原自然植被恢复问题出发．引出植被恢复的参照标准-潜在自然植被。依据气象站和雨量站观测资料，建立气温降水与海拔高度和地理位置的统计方程，以GIS为技术支撑．对两大环境变量进行空间化．通过野外观测取样，结合气温降水的空间分布，界定祖厉河流域不同草地覆盖度的生境空间。根据生境空间边界函数，对整个流域内的潜在草地植被分布进行模拟。草地分布现状与潜在草地分布对比发现，低覆盖草地南北向南扩展，占潜在中覆盖草地面积的37139％．占潜在高覆盖草地面积的34．98％。中覆盖草地也在此向南部区域和北部山地扩展，占潜在高覆盖草面积的11．51％。高覆盖草地收缩到南部和北部山地狭小地带．仅占其应有区域的4．84％。

英文摘要：

There has been an increasing use of predictive spatial distribution of main communities or dominant species at the regional scale for ecological restoration planning, biodiversity conservation planning and regional management decisions on the Loess Plateau. Understanding the spatial distribution of main communities at the regional scale is also essential in assessing the impacts of environmental change or human impacts on vegetation distribution. Based on the investigation of steppe cover that correlates with its habitat, this study focused on the prediction of steppe distribution in the Zulihe River watershed of the west-central Loess Plateau. First, we investigated the cover of steppe of 365 samples. Secondly, important variables （annual mean precipitation and annual mean temperature） that affect vegetation distribution were spatialized as functions of elevation and horizontal coordinates via a GIS. Thirdly, the niche spaces of steppe were determined by incorporating the spatially-distributed main variables with the steppe cover that came from field investigation and remote sensing data （Landsat TM image）. The niche spaces defined then were extrapolated over the study area. Comparing the distribution of predicted steppe with its present distribution, we found that the natural vegetation in the region has been destroyed and disturbed by human activities. As a result, soil erosion has been aggravated. The ecological conditions in the study area have been progressively degraded by human-accelerated soil erosion. The object of the study is to provide important baseline for ecological restoration in the Zulihe River watershed.