基于GIS和几何平均数模型的流域生态安全评估及在各因子中的分异特征——以星云湖流域为例

结合几何平均数模型和GIS技术,选取海拔高程、坡度、土壤侵蚀强度、地质灾害易发性、土地利用类型、植被覆盖度、距自然生态保护区距离、距离建设用地、人口密度和距水源距离10个指标对星云湖流域生态安全进行评价,分析了该区域生态安全的空间分异规律和形成机理。研究表明:星云湖流域平均生态安全指数为2.33,中度安全面积占流域总面积的42.34%,高度安全占22.84%,较低安全占26.43%,不安全面积为32.117km~2,占8.39%,说明流域生态安全总体以中度安全为主,生态系统健康一般;从空间上,流域生态安全较低区主要集中分布于北部、东部和南部以及城市建筑密集区,除了城市建筑密集区受人类干扰较强外,其余地区坡度和地形起伏较大,景观较为破碎,水土流失较为严重且有过地质灾害发生,这些地区是生态保护和建设的重点区域。生态安全等级在综合评价下的结果与单因子评价下的结果存在较大差异,区域生态安全受多重因素的综合影响,单因子评价难以精确全面反映区域生态安全的空间分异规律特征和成因机理,各因子之间存在相互促进和相互抑制的作用关系,流域自然环境要素坡度、水资源环境和水土流失以及人类活动干扰要素土地利用格局、距离建设用地远近等因子是形成流域生态安全格局的主要因素。

An Assessment on Basin Ecological Security and Its Variation Characteristics in Factors Based on GIS Technique and Geometric Mean Model——A Case in Nebula Lake Basin

The 10 factors includes elevation,slope,soil erosion intensity,prone to geological disasters,land use types,vegetation coverage,distance from the natural ecological protection zone,the distance of construction land,population density and the distance from the water were selected to evaluate the ecological security of Nebula Lake Basin.The spatial distribution and formation mechanism of regional ecological security was analyzed by using the geometric mean model and 3S technology tentatively.The study showed that the average ecological security index was 2.33 in Nebula Lake basin.From the aspect of area proportion of all security levels,the area of moderate security zone accounted for 42.34％,high security for 22.84％,the low security for 26.43％,the unsafe for 8.39％ of the total basin area,which illustrated that ecological security was mainly moderate security in the basin;from spatial distribution aspect,the zone of higher ecological security mainly distributed in the northern,eastern and southern and built-up zones in Nebula Lake basin where the slope gradients of land are great,terrain was undulated,the forest landscape was fragemental,land use was not reasonable,soil erosion was severe,and geological disasters has happened except that the city building intensive area was disturbed by the human,these regiions are the key areas of ecological protection and construction;there is a big difference between the two results that the regional ecological security is affected by multiple factors,single factor evaluation is difficult to accurately reflect the characteristics and mechanism of spatial differentiation of the regional ecological security through the comparison and analysis between the results of comprehensive evaluation and single factor evaluation.There is the relationship of mutual promotion and inhibition among each factor.The factors such as slope,water resource environment,soil and water loss and disturbance factors of human activities such as land use pattern,distance from construction land are the main factors to form the ecological security pattern of the basin.