三峡库区重庆段土地生态状况时空格局演变特征

以三峡库区重庆段为研究对象,基于“基础-结构-效益-胁迫”框架构建了土地生态状况评估指标体系,利用变异函数理论模型对研究区2000年、2009年、2014年土地生态状况综合指数进行了拟合分析,通过空间自相关、冷热点分析及转移矩阵分析方法,分析了2000—2014年研究区域土地生态状况的时空演化规律。结果表明:(1)研究区土地生态质量呈现出库区腹地、库区中部、库区尾部依次降低的分布特征,且2000—2014年呈现出快速恶化-缓慢逆转的变化过程。(2)研究区2000—2014年C0/(C0+C)先减后增,呈中等空间自相关,表明结构性因素引起的空间异质性起主要作用;但随机性因素对土地生态状况的空间分异影响亦不可忽视,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)从Moran′sI值判断,2000—2014三峡库区重庆段的土地生态状况在区域上一直处于较高的集聚状态,2000—2009年集聚增强,2009—2014年集聚减弱。(4)从冷热点分析结果来看,2000—2014年,热点区域、冷点区域范围总体上均呈现出逐渐增加的趋势,但在空间上表现出了一定的分异特征:库区尾部的热点区域不断拓展,而库区腹地的热点区域则表现出逐年减小的趋势;且研究区热点区域主要集中分布在库区尾部的主城区和库区腹地万州区的中心城区,冷点区域主要分布在库区腹地的巫山县、巫溪县、奉节县、开州区和库区中部的石柱县、丰都县、武隆区等土地利用程度相对较弱、植被覆盖相对较好地区。

Spatiotemporal variation in the ecological status of the Three Gorges Reservoir area in Chongqing, China

The Three Gorges Reservoir Area (TGRA) of Chongqing 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. The ecological environment of the TGRA is directly related to the safety of the Three Gorges Project, stability of millions of immigrants, ecological security of the Yangtze River Basin, and sustainable development of the region''s social economy. The study on the characteristics of the spatiotemporal evolution of land ecological status in the TGRA of Chongqing has certain reference value for further strengthening the regional land ecological environment protection, which is of great significance for the understanding and solution of the current national ecological security strategy issues that are highly concerned. The aim of the present study was to develop an index system for assessing the land ecological status of the TGRA of Chongqing using the "basic-structure-benefit-stress" framework, to use a theoretical model of variation to fit and analyze the comprehensive index of land ecological status in 2000, 2009, and 2014, and to use spatial autocorrelation to perform hot and cold spot analysis and transfer matrix analysis of the spatiotemporal evolution of land ecological status in the study area from 2000 to 2014. (1) The quality of the land ecological status in the study area shows the distribution characteristics of the inner section of the TGRA > the middle sections of the TGRA > the end sections of the TGRA, and the process of rapid deterioration-slow reversal was exhibited in the TGRA of Chongqing from 2000 to 2014.(2) The C₀/(C₀+C) ratio initially decreased but then increased from 2000 to 2014, thereby indicating medium spatial autocorrelation and that spatial heterogeneity caused by structural factors played a major role in the spatial differentiation of land ecological status. However, the impact of random factors on the spatial heterogeneity of land ecological status cannot be neglected, which is consistent with rapid economic development, intensified use of land resources, and frequent occurrence of regional natural disasters during the past 14 years. (3) The evaluation of Moran''s I values indicated that the land ecological status of Chongqing''s TGRA during 2000-2014 has been in a high state of agglomeration, which increased during 2000-2009 and decreased during 2009-2014. (4) The areas of both the hot and cold spots generally increased from 2000 to 2014 but differed in spatial differentiation. The hot spots in the end section of the TGRA continuously increased, whereas the hot spots in the inner section of the TGRA continuously decreased. The hot spots were mainly concentrated in the main urban area in the end section of the TGRA and central urban area in the Wanzhou District, the inner section of the TGRA. The cold spots were mainly distributed in the inner sections of the TGRA in Wushan County, Wuxi County, Fengjie County, and the Kaizhou District and in the middle section of the TGRA in Shizhu County, Fengdu County, and the Wulong District, where the extent of land use is relatively low and vegetation coverage is relatively high. To some extent, the cluster characteristics of the hot and cold spots in the land ecological quality status reflect the differentiated land resource utilization policies and different regional development strategies of the TGRA of Chongqing.