快速城市化地区景观生态安全时空演化过程分析——以东莞市为例

依托“压力-状态-响应”概念框架模型,建立景观生态安全评价指标体系,以东莞市为例,研究区域景观生态安全时空发展变化过程,揭示快速城市化地区生态安全发展变化的规律.结果表明:1988、1997和2005年东莞市的平均生态安全综合指数分别为0.497、0.436和0.395,区域总体生态安全从中高安全状态逐步降低到中低安全状态;生态中低安全的区域空间上从“市中心-镇中心”沿“市中心-镇中心-道路”不断扩张.采用以像元为中心的公里网格滑动模板的指标作为像元的评价指标,可以有效解决景观结构指数等指标的计算,在生态安全等级划分时边界过度很平滑,景观尺度的生态安全评价可以为生态可持续发展政策的制定提供科学依据.

Landscape ecological security dynamics in a fast growing urban district: the case of Dongguan City

Based on the "pressure-state-response" conceptual framework, an evaluation system is proposed to study landscape ecological security dynamics from 1988 to 2005 in Dongguan City, a fast-growing city in Guangdong Province, China. The pressure index, which describes the pressure that human activities exert on the environment, consists of urban development intensity, population density, distance to major transportation routes, distance to nearest city center and distance to nearest town center. The landscape security state index, which relates to the quality of the environment, is composed of landscape patch density, ecological service value, and landscape vulnerability. The response index, which reflects the reaction of human beings to landscape dynamics, is defined as adjusted intensity of natural reserve districts, forest, park, and crop lands. The evaluation units are Landsat TM pixels and the fundamental data set is obtained by classifying raw TM data. Transportation and city-center location data are obtained from topographic maps. Population, environmental protection, planning, and other data are obtained from the Dongguan statistical yearbook and the Dongguan Department of Environmental Protection. The results for Dongguan City indicate that the pressure index was 0.317, 0.394, and 0.472 in 1988, 1997 and 2005 respectively, which means the landscape pressure increased from 1988 to 2005. The landscape security state indicator was 0.473, 0.406 and 0.365 in 1988, 1997 and 2005, which means landscape security became more insecure. The response to ecological security dynamics was steady from 1988 to 2005. The weighted sum of the pressure index, the landscape security state index, and the response index is the integrated ecological security index which was 0.497, 0.436 and 0.395 in 1988, 1997 and 2005. In short, ecological security declined from 1988 to 2005. The districts with middle-low ecological security expanded outwards from primarily town center locations in 1988 to outlying urban areas and along major transportation routes by 2005. The high ecological security districts, which consist of reservations, forest land, parks, and rivers, were steady from 1988 to 2005. The study indicates that the pixel evaluation unit based on 1 km×1 km neighborhoods is useful for calculating urban development intensity and landscape patch density, and in smoothing the ecological security grade boundary.