基于GIS格网模型的银川市土地生态安全评价研究

为探索市域范围内土地生态安全的粒度特性及其空间效应,论文结合PSR理论框架构建评价指标体系,以公里格网为评价单元,采用熵权法计算区域土地生态安全综合指数。银川市的实证分析表明,2014年整个区域土地生态安全指数为0.488 2,市域范围内土地生态安全存在着空间异质性和结构功能分化的双重特征。从宏观行政区划层面来看,3个中心辖区表现相对较为均衡,2个郊区县差异性较大,仅有贺兰县(0.557 7)高于全市均值;从微观格网尺度来看,北部和城市中心的综合指数较高且呈离散分布,城市边缘区较低且呈集聚分布;从土地利用功能区的角度来看,农业区、城市建城区、湿地和自然保护区的核心区域综合指数较高,而功能边缘区与交叉区较低,土地生态安全和土地利用方式存在耦合关系。通过ESDA空间分析表明,格网尺度下土地生态安全全局Moran’s I指数为0.780 4,生态安全的空间格局表现出空间连续性和聚集效应。因此,从空间建构的视角来看,应充分利用"高高聚集"区的空间扩散和溢出效益,并通过逐步改善影响"低低聚集"区的限制性因子,实现区域内部土地生态安全格局的优化配置。

Assessment of Urban Land Ecological Security in Yinchuan City Based on the Grid Method

To explore the spatial effect and scale characteristics of the land ecological system within the scope of the city, this paper constructs a scientific evaluation system of land ecosystem based on PSR model. The basic unit of the evaluation system is 1 km×1 km grid. Entropy method is used to calculate the regional land ecological security index. We assess the land ecological security index in Yinchuan city, and the results show that the regional land ecological index is 0.488 2 in 2015. The land ecological security has dual characteristics which includes structure function differentiation and spatial heterogeneity. From the macro perspective, the gaps among the three central districts are very small, while the difference between the two suburban counties is very large. Only the ecological security value of Helan County (0.557 7) is higher than the overall average in the city. From the micro perspective, there is a certain relationship between land ecological security and the way people use the land. At the micro level, the composite index in the north and center of the city was higher, while it is lower at the fringe of the city. From the view of land use function, the core composite indexes of agricultural areas, urban built-up areas, wetlands and nature reserves are higher, while the index in cross-functional areas is very low. There is coupling relationship between the land ecological security and the land use pattern. The important factors of land ecological security in Yinchuan include per capita arable land area, industrial structure and pollution control efforts, etc. By ESDA spatial analysis, the global Moran’s I of land ecological security in Yinchuan city is 0.780 4, which means inherent spatial correlation of ecological security. The land ecological security in Yinchuan city as a whole has characteristics of spatial continuity and spatial dependence. Therefore, we should make full use of the spatial diffusion and spillover benefits in high-high aggregation area, and improve the restriction factors in low-low aggregation area, so as to reduce the environmental risk and optimize the allocation of space.