Abstract: In order to explore the specific distribution characteristics of terrain factors in purple soil region, based on ASTER GDEM(30 m resolution ratio), this paper extracted and analyzed the distribution characteristics of terrain factors, including slope gradient, slope length, slope and length factor (LS factor) and gully density, etc. terrain factors by spatial analysis tools of ArcGIS. The results showed that the proportion of steep slope (>15°) was 58% in the whole region, that in Qinba mountain region was the largest, reaching 80%; that in the regions with slope length within the scope of 0~40 cm took 60%, mainly concentrated in Sichuan and Chongqing mountain hilly regions. The proportion with LS factor value >15 was 55%, mainly distributed in Qinba mountain region and Wuling mountain and hilly regions, with the same slope distribution. The gully density of purple soil region was 0.69 km/km2, that in Sichuan and Chongqing mountain and hilly regions were the least, only 0.57 km/km2, being inferior to 17.39% of the average scale gully density value. The results provided scientific basis for soil erosion assessment, soil erosion prediction, and ecological repair and reconstruction in the purple soil regions.

Key words: terrain factor, characteristic, GIS, purple soil region, statistic analysis

摘要： 为探索紫色土区地形因子的具体分布特点，基于ASTER GDEM（30 m分辨率），利用ArcGIS软件的空间分析等工具，提取并分析紫色土区坡度、坡长、坡度坡长因子（LS因子）、沟壑密度等地形因子的分布特征。结果表明：全区＞15°的陡坡占比达58％，其中秦巴山山地区陡坡占比最大，达80%；坡长在0~40 m范围内占比达60%，主要集中在川渝山地丘陵区；LS因子值>15的陡坡占比达55%，主要分布在秦巴山山地区与武陵山山地丘陵区，与坡度分布一致；区域尺度的沟壑密度为0.69 km/km2，其中川渝山地丘陵区沟壑密度最小（0.57 km/km2），低于区域尺度沟壑密度均值的17.39%。研究结果可为紫色土区水土流失评价、土壤侵蚀预报及生态修复与重建提供科学依据。

关键词: 地形因子, 特征, GIS, 紫色土区, 统计分析