三峡库区生态敏感区土地生态安全预警测度与时空演变——以重庆市万州区为例

Measures of land ecological security early warning and its spatial-temporal evolution in the ecologically sensitive area of the Three Gorges reservoir area: A case study of Wanzhou District,Chongqing City

以三峡库区生态敏感区典型区万州区为研究对象,基于压力-状态-响应(P-S-R)框架构建土地生态安全预警指标体系,运用熵值法进行土地生态安全预警分析,并通过空间统计学方法对研究区土地生态安全警度的空间分布特征、变异规律及空间关联格局进行研究分析,旨在为区域土地资源利用的规划、管理及其生态保护提供决策参考。结果表明:(1)研究区2000-2014年土地生态安全警度呈连续上升趋势,土地生态安全警度较高区域由万州区中心城区不断向四周扩散,但2000-2009年期间研究区土地生态安全警度提升幅度比2009-2014年期间更为明显,2000-2009年期间是区域土地生态安全警度变化的关键时段。(2)研究区2000-2014年C_0/(C_0+C)呈不断上升趋势,表明非结构性因素对区域土地生态安全警度的影响程度在不断加大,这与研究区14年来经济高速发展、人类对土地资源利用强度加剧以及区域自然灾害频发的实际情况相符。(3)研究区2000年、2009年、2014年全局Moran's I值分别为0.7823、0.7772、0.775,表明土地生态安全预警指数在空间上存在较强的正相关关系,区域土地生态安全警度在空间上具有较强聚集性。(4)研究区"高-高"、"低-低"值区均呈现出2000-2009年范围逐渐增加,而2009-2014年范围逐渐缩小的趋势;且"高-高"值区主要集中分布在中心城区及其邻近区域,"低-低"值区则主要集中分布在研究区西北部和东南部等土地利用程度相对较弱、植被覆盖相对较好地区;中心城区周边的"低-高"值区将是城市发展中优先被占用的区域,在未来的土地利用中,尤其需加强对区域"低-高"值区的重点保护。

The ecologically sensitive area of the Three Gorges reservoir area is located in the throat area of the ecological barrier in the Yangtze River Basin, which is one of the key areas for biodiversity conservation in China. It is also the western hub of the economic belt of the upper Yangtze River. The contradiction between resource protection and economic development has become increasingly prominent, and thus, the problem of an early warning for land ecological security is worthy of attention. Because of the considerable significance of understanding and finding a solution to current problems concerning the national ecological security strategy, there is a certain reference value for determining the degree of early warning for land ecological security and examining its temporal and spatial evolution in the ecologically sensitive area of the Three Gorges reservoir area, thereby further improving the regional warning for land ecological security. An early warning indicator system for land ecological security was established based on a pressure-state-response （PSR） framework. An entropy method was then used to analyze the early warning for the ecological security of land in the Three Gorges reservoir area, Wanzhou District. In addition, using spatial statistical methods, the spatial distribution and variation, and spatial correlation pattern of the degree of alarm for land ecological security in the study area were evaluated and analyzed. The aim of the study was to provide a decision-making reference for the planning, management, and ecological protection of regional land resource utilization. The results obtained were as follows. （1） The warning degrees for land ecological security in the study area in the period 2000-2014 showed a continuous upward trend, and the area with a higher land ecological security alarm continued to spread from the central city to the surrounding Wanzhou District. However, improvement in the range of the land ecological security alarm in the period 2000-2009 is more obvious than that in the period 2009-2014. It is, therefore, clear that 2000-2009 is the key period for the change in land ecological security. （2） The ratio of C0/（C0＋C） in the study area increased from 2000 to 2014, indicating that the impact of non-structural factors on regional land ecological security continues to increase. This is consistent with the rapid economic development, the intensified use of land resources, and the frequent occurrence of regional natural disasters in the past 14 years. （3） The global Moran＇s I of the study area in 2000, 2009, and 2014 was 0.7823, 0.7772, and 0.775, respectively, which indicates that there is a significant positive correlation among the land ecological security warning index on a spatial scale, and that the degree of regional land ecological security warning has a strong clustering at the spatial scale. （4） The areas of ＂high-high＂ and ＂low-low＂ in the study area showed a gradually increasing trend from 2000 to 2009 and a decreasing trend from 2009 to 2014. Furthermore, the ＂high-high＂ areas are mainly distributed in the central city and the adjacent areas, whereas the ＂low-low＂ areas are mainly located in the northwest and southeast regions of the study area, where the extent of land use is relatively low and vegetation coverage is better than that in other areas. The ＂low-high＂ areas around the central city will be a priority area for urban development. In terms of future land use, it will, therefore, be necessary to strengthen the protection of the ＂low-high＂ areas.