湘乡市生态安全评价研究

Ecological security evaluation of Xiangxiang city

以位于湖南省中部的典型低山丘陵区县级市——湘乡市为研究对象,从高程、坡度、地形起伏度、土地利用类型、NDVI、到河流距离、到公路距离、降雨量、生物多样化、土层厚度、粮食产量等14个指标构建生态安全评价指标体系,提出基于随机森林(RF)的生态安全评价模型,结合GIS技术以50 m×50 m栅格作为评价单元识别出湘乡市生态安全水平极其重要影响因素。结果表明,湘乡全市生态安全水平处于中低水平,中低水平的栅格占比为84.33%。生态安全水平空间分布不均,整体呈现西、北部地区高于东、南部地区,丘陵区高于平原,山区高于城区的特点。影响湘乡市生态安全水平的主要因子按重要性程度依次是生物多样性、到公路距离,到河流距离和土地利用类型;土层厚度、土壤可蚀性、石漠化程度等因子对生态安全等级评价的影响相对较小。本研究构建的随机森林生态安全评价模型的样本训练精度为98.01%,测试精度为95.53%,具有较高准确率。

Xiangxiang city,a typical county-level city located in the central part of Hunan province,was taken as the research ob⁃ject,and the ecological security evaluation index system was constructed from 14 indexes,such as elevation,slope,topographic re⁃lief,land use type,NDVI,distance to river,distance to highway,rainfall,biodiversity,soil thickness,grain yield,etc.An ecological security evaluation model based on random forest(RF)intelligent algorithm was proposed,which combined with GIS technology to evaluate the ecological security of 50 m×50 m grid was used as the evaluation unit to identify the extremely important factors affecting the ecological security level of Xiangxiang city.The results showed that the ecological security level of Xiangxiang city was in the mid⁃dle and low level,and the proportion of low and medium level grid was 84.33%.The spatial distribution of ecological security level was uneven,which was higher in the west and north than in the east and south,higher in the hilly area than in the plain,and higher in the mountainous area than in the urban area.The main factors affecting the level of ecological security in Xiangxiang city were biodiver⁃sity,distance from highway,distance from river and land use type in order of importance.Soil thickness,soil erodibility,rocky desert⁃ification degree and other factors had relatively little influence on the evaluation of ecological security level.The sample training accuracy of the random forest ecological security evaluation model was 98.01%,and the test accuracy was 95.53%,which had a high accuracy.