环京津贫困带土地利用变化的地形梯度效应分析

地形因素与土地利用变化的关系研究是土地利用/覆被变化研究的重要内容。该文以环京津贫困带为研究区,选取1985年、1995年、2000年和2010年Landsat TM影像为数据源,运用地学图谱分析法,从地形起伏度、坡度变率、坡向和地形位角度,系统分析了环京津贫困带土地利用变化的地形梯度特征,探讨了土地利用变化的地形梯度效应及其成因。结果表明:1)1985-2010年环京津贫困带土地利用类型分布呈现明显的层级性。耕地、水域和建设用地的优势分布区集中于低地形梯度区,草地优势分布区集中于中高、高地形梯度区,林地和未利用地优势分布区集中于高地形梯度区。2)研究区土地利用变化以稳定型图谱和反复变化型图谱为主,林地、耕地和草地是主要的土地利用类型,林地向耕地转换再又转换为林地是反复变化型图谱的主要类别。1985-2000年人地矛盾突出,土地利用变化以"林地-耕地"、"草地-耕地"和"未利用地-耕地"为主,耕地向较高地形梯度区扩展;2000年后社会经济发展和退耕还林政策的实施,土地利用变化以"耕地-建设用地"、"耕地-林地"和"草地-林地"为主,耕地在原优势地形位的优势度增大、草地和未利用地的优势分布区向更高级地形位集中,林地优势分布区向较低地形位扩张。3)土地利用变化地形梯度分布特征及分异效应是自然因素、社会经济因素和政策因素共同作用的结果,自然因素是基础,社会经济因素和政策因素是重要推动力。该文为研究区土地利用动态优化配置和生态环境建设提供了科学依据和决策支持。

Terrain gradient effect analysis of land use change in poverty area around Beijing and Tianjin

Abstract: Being the core of the study on global environment change and sustainable development, land use/cover change (LUCC) gains more and more attention. The pattern of land use and its spatial-temporal change plays an important role in the study on land use/cover change. As global environment deteriorates, the study on land use change and its driving forces becomes an important research subject in the field of land science. The relationship between terrain variables and land use has become an important part of land use/cover change. Based on the remote sensing data of TM images in 1985, 1995, 2000, and 2010, we took the poverty area around Beijing and Tianjin as an example to analyze the terrain gradient characteristics of land use change by geo-informatics map analysis. In order to provide some recommendations on land use planning and land use management, we also explored the impact of topography on the selection of land use pattern and the causes of the terrain gradient effect of land use change. The results showed that 1) From 1985 to 2010 the land use types mainly distributed on the area of terrain relief under 200 m as well as slope of slope (SOS)) less than 15°. During the past 25 years, arable land, forestland and grassland were the dominant land use types. The areas of arable land, grassland and unused land decreased constantly, while the areas of forestland and construction land increased gradually. 2) The hierarchy was shown obviously in the distribution of land use types along the terrain gradient in poverty area around Beijing and Tianjin. Arable land, water area, construction land mainly were distributed on the area of low terrain gradient. The grassland mainly was distributed on the area of medium and high terrain gradient, while forestland and unused land mainly covered the high terrain gradient. 3) The construction land was obviously confined by the terrain niche, which was mainly located in the low terrain gradient area. While arable land acted as the main resources for transforming to construction land in the same area, it expanded to higher terrain gradient area in order to make up the area occupied by the construction of infrastructure facilities. The forestland was well restored in the area of higher terrain gradient, which expanded to mid-high terrain gradient area with the project of returning arable land to forestland. In addition, the predominant distribution area of unused land and grassland became gradually diminished. 4) The terrain gradient effect of land use change was the result of comprehensive effect of natural, socio-economic and policy factors. The natural factors played a key role in the formation of the terrain gradient effect of land use change. Socio-economic factors and policy factors were important push-drivers, such as human migration, construction of infrastructure facilities, and the project of returning arable land to forestland. This research was important in easing the conflict between human and the surrounding environment, and it was meaningful to the sustainable development of land resources in order to keep the ecological balance of the studied region. The study provided some alternatives for the dynamic optimal allocation of land use and the construction of eco-environment of the poverty area around Beijing and Tianjin.