基于土地利用变化的辉南县生态脆弱性时空变化分析

摘要

山区平原过渡地带因其地质、地貌的特殊性而担负着自然地域界面的作用，并表现出更高的生态环境脆弱性，研究其脆弱性变化对山区平原生态安全预警非常重要。特别是从土地利用方式改变评价其生态脆弱性，对于土地利用方式调整和规划具有重要指导意义。本文以地处山区平原过渡区的辉南县为例，在分析其土地利用变化基础上，参照生态价值评估体系并结合周围生态环境敏感因子，建立生态脆弱性综合评价指标，对研究区1986年以来环境脆弱性的时空变化进行评价和分析。评价结果如下：（1）从不同用地类型看，生态综合指数大小顺序依次为林地、草地、水域、未利用地，其次是耕地和建设用地。（2）脆弱性时间变化特征：由于土地利用变化，特别是林地减少和耕地、建设用地增加，导致生态贡献指数、生态稳定性指数和生态综合指数显著下降，分别由1986年的2.999、3.324和6.322减小为2006年的2.828、3.032和5.861。（3）空间变化特征：全区范围内生态环境综合指数下降显著，表现为低值区域范围扩大，高值区域范围明显减小。高值区范围由1986年的33217.95ha缩小为2006年的1283.40ha，而低值区的范围则由1986年的86550.87ha扩大为2006年的98084.83 ha。（4）地区差异性：虽然三个生态指数在整体上呈现下降，但是不同子流域其变化表现出显著的差异性，总体上呈现东南山区减小，而西北平原区呈现不明显的增加特点。本文研究结果表明，导致研究区生态脆弱性的主要原因为林地减少和耕地增加。从保护生态环境角度，控制耕地增加和林地减少是有效防范措施。%The ecological environments in mountain plain transi-tion zones appear more vulnerable considering the transitional geology and geomorphology conditions. It is vital to study the eco-vulnerability of this special zone for the whole zone's ecologi-cal safety. Especially from land use to understand the eco-vulner-ability, it is feasible to plan land use and land cover in order to protect the eco-environments. The Huinan County which locates in this zone is taken as study area, based on the analysis of land-use changes, the spatial-temporal characteristics on ecological vulnerability are assessed by using ecological synthetical index which is built according to the evaluation system of ecological value and sensitive factors. The results show that:1) According to the types of land-use, the order of ecological synthetical index is forest land, grass land, water body, unused land, cultivated land and construction land. 2) During the past 20 years, because of the great change of land cover, especially the decreased forest and the increased cultivated land & construction land the value of land use contribution index, land use stability index and ecological synthetical index decreased markedly, from 2.999,3.324 and 6.322 to 2.828,3.032 and 5.861 respectively. 3) The spatial characteris-tics on ecological vulnerability change markedly, the mild vulnera-bility area increase while the severe vulnerability area decrease obviously, detailed description listed as follows: the mild vulnera-bility area increases from 86550.87 to 98084.83 and the severe vulnerability area decreases from 33217.95 to1283.40 during the past 20 years. 4)all the three ecological indexes of the whole study area decrease. However, great different changes vary obviously in different catchments, which decrease in the southeast region while increase in the northwest ones obviously. From the results we are told that forest land decrease and arable land increase are the main reasons which cause the eco -vulnerability. Reasonable measures for land use plan could be taken to control the land use changes.