基于GIS的宁夏中部干旱带土地利用生态安全动态评价

土地利用生态安全评价是区域可持续发展关注的重要内容之一。以宁夏中部干旱带为例,针对研究区实际生态问题,基于RS和GIS技术,构建"隐患—状态—免疫"生态安全评价指标体系,采用熵权法与综合指数模型,实现了30m×30m栅格水平可视化的土地利用生态安全综合评价。结果表明:2004—2014年,研究区土地利用变化和区域政策的实施结果一致。草地、林地面积急剧扩大,旱地和未利用地面积持续下降,建设用地和水域面积变化不大,水浇地面积呈缓慢增加趋势。结合已有研究成果与研究区实际,采用聚类法,将研究区土地利用安全分为5个等级:生态安全区(Ⅰ)、生态较安全区(Ⅱ)、生态临界安全区(Ⅲ)、生态不安全区(Ⅳ)和生态极不安全区(Ⅴ)。研究区土地利用生态安全指数从2004年的-0.12上升为2014年的0.03,整体状态呈变好趋势,但ESI指数仍小于0.1,处于临界安全状态。具体表现为:Ⅰ级乡镇从4个增加为5个、Ⅱ级区从10个增至11个、Ⅲ级乡镇从13个减少为12个、Ⅳ级乡镇从5个减少为4个、Ⅴ级乡镇从8个减少为7个,针对评价结果分析其动态演变机制。通过对宁夏中部干旱带土地利用生态安全动态评价,以期为宁夏境内生态移民区选址和生态环境保护提供数据支撑。

Land Use Change and Ecological Security Assessment of the Central Arid Zone in Ningxia Based on GIS

The assessment of land use is one aspect of the studies on sustainable development.In order to testify these views,a case study was conducted in the central arid zone in Ningxia.The existing ecological problems and major ecological processes were analyzed,as well as land use/cover change and its effect on soil erosion,ecological water requirement and biodiversity were explored by using RS and GIS techniques combining with field investigation in this study.We analyzed land use change in the central arid zone in Ningxia from 2004 to 2014,and then established an evaluation index system on the basis of Hazard-State-Immune model.Entropy methods were used for determining index weights,for evaluating ecological security on 30 m× 30 m grid scale in the period from 2004 to 2014.The results of the study were as follows.The change of land use followed the regional policy,the areas of grassland,woodland expanded largely,the areas of farmland and unused land kept decreasing,construction land and water area were almost same,irrigated land increased slowly.Combined with the existing research results and practical situation,based on cluster analysis methods,ecological security assessment grade in the research area can be divided into five levels:the area of very security(Ⅰ),relative security area(Ⅱ),critical security area(Ⅲ),relative insecurity area(Ⅳ),very insecurity area(Ⅴ).From 2004 to 2014,the land ecological composite index showed the increasing trend,but the ESI index was still less than 0.1 and showed critical security state.The area of very security towns increased from four to five,relative security villages increased from ten to eleven,critical security towns decreased from thirteen to twelve,relative insecurity town decreased from five to four,very insecurity towns decreased from eight to seven with respect to the evaluation results to analyze its dynamic evolution mechanism.The study results may provide the data support and basis for choosing the ecological immigration sites and ecological environment protection in Ningxia.