长期以来，由于不合理的土地利用、掠夺式的经营方式以及林草植被的过度开垦，黄土丘陵沟壑区已经成为一个生态环境脆弱，社会经济落后，人地矛盾十分突出的地区。安塞县地处黄土丘陵沟壑区，梁峁起伏，沟壑纵横，地表支离破碎。该地区长期以来人地矛盾突出，土地资源的稀缺性以及土地利用过程中的不合理性是造成当地水土流失、生态环境恶化的重要原因。因此，根据该区域的土壤流失特性，优化调整土地利用格局，有助于提出适合该地区的土地可持续利用模式，改善区域的生态系统服务功能，提高区域生态安全，为今后开展区域综合治理和土地利用规划提供科学依据。本研究选取土壤侵蚀评价指数（SL 指数）作为评价模型，在探讨县域尺度SL 指数的GIS 实现技术基础上，对安塞县1981-1989 年土壤侵蚀进行了定量评价，分析得出了该地区土壤侵蚀评价指数及其空间分布特征，识别出该区域内土地利用格局重点优化区域。在此基础上，采用线性规划和元胞自动机对安塞县土地利用格局进行调整优化，模拟出2010 年安塞县土地利用格局。主要结论如下：(1) GIS 技术能够为土壤侵蚀定量评价提供强大、有效的技术支持。通过ArcGIS 软件对DEM 数据、土地利用数据和空间数据库的处理，在分析各土壤侵蚀因子的基础上，计算出土壤侵蚀评价指数，能够很好地反映出土壤侵蚀在安塞县范围内的空间分布特征。(2) 安塞县1981 年-1989 年间多年平均降雨侵蚀力约为9510.27MJ·km-2·h-1·a-1。安塞县所处地区降雨季节变异十分显著，降雨主要集中在7、8 两月，其降雨侵蚀力均在2400MJ·km-2·h-1·a-1 以上，而汛期以外8 个月份的降雨侵蚀力之和仅为1400MJ·km-2·h-1·a-1左右，仅占全年降雨侵蚀力的15.3%。同时，安塞县降雨分布有明显的方向性，总体来说安塞县范围内降雨侵蚀力从北向南是逐渐增大的。(3) 基于坡面尺度土壤流失比率和降雨侵蚀力的季节分布，通过尺度上推计算出县域尺度植被覆盖与管理因子，其全县平均值约为0.36，在空间分布上东部略微比西部高，这与土壤流失比率的空间分布特征相似。(4) 通过对各侵蚀因子的空间叠加分析，计算得到安塞县全县平均土壤侵蚀评价指数为0.36。根据此结果采用总分频率曲线法，对安塞县地区进行土地利用格局重点调整区域的识别，将安塞县划分为三类地区：SL≤0.28，0.28 ﹀

Because of irrational land use, plunderous utilization and excessive reclamation of forest and grass vegetation for a long time, the hilly and gully area of the Loess Plateau has become an area with fragile ecological environment, behindhand society and economy, and severe conflict between population and land resource. Located in the hilly and gully area of the Loess Plateau, Ansai County has a hypsographic feature, crisscross gulley and fragmented landform. At the same time, this region has a long history of land development, but with a thousand-years plunderous reclamation system and deforestation, forest and grass vegetation sharply decreased, as well as severe soil and water loss these years. Therefore, according to the soil loss characters of the region, optimization for land use pattern will help to put forward a way of land sustainable use pattern, to improve regional ecosystem service function, to enhance regional ecological security, and offer a scientific basis for regional comprehensive treatment and land use planning in the future. Soil loss evaluation index was chosen as the evaluation model in this essay. Based on the GIS implementation technology of county scale model, soil erosion of Ansai County form 1981 to 1989 was evaluated quantitatively. Soil loss evaluation index and its spatial distribution characters of this region were analyzed. It was identified the key optimize region of land use pattern. On the basis, using linear planning and cellular automata, study optimized and adjusted land use pattern of Ansai County, and simulated land use pattern of Ansai County in 2010. The main conclusions were as followed: (1) GIS technology can make a strong and efficient technological support for land erosion quantitative evaluation. Using ArcGIS software to process DEM data, land use data and spatial database, calculating soil loss evaluation index based on analyzing soil erosion factors, can reflect the spatial distribution of soil erosion well in the range of Ansai County.(2) The rainfall erosivity mean between 1981 and 1989 in Ansai County fluctuated every year, was about 9510.27MJ•km-2•h-1•a-1. Seasonal rainfall changed remarkably in Ansai County , where rainfall was mainly in June and July, with rainfall erosivity of over 2400MJ•km-2•h-1•a-1, while the sum of rainfall erosivity in eight months beyond flood season was about 1400MJ•km-2•h-1•a-1, accounting for 15.3 percent of the whole year’s rainfall erosivity. In the meantime, rainfall distribution had an obvious directivity. Generally speaking, the rainfall erosion force was increased form north to south in the range of Ansai County.(3) Based on the method of calculating C value in the slope scale, which was weighted average calculated by the soil loss rate and seasonal rainfall erosivity. cover-management factor in county scale were calculated by upscaling, which average value was about 0.36. In the spatial distribution aspect, eastern value was higher than western, which was similar to soil loss rate spatial distribution.(4) By spatial overlay analysis of every erosion factors, soil loss evaluation index mean of Ansai County was 0.36. According to this result, using total frequency curve method, find out the area where land use pattern should be mainly adjusted. And Ansai County was divided into three area: SL≤0.28, 0.28 ﹀