快速城镇化地区土地利用变化的地形梯度特征分析——以榆次区为例

为探讨快速城镇化地区——山西省晋中市榆次区不同地形梯度上的土地利用变化特征,本研究以2000年、2008年和2016年3期影像和ASTERGDEM为数据源,分析2000—2016年间土地利用变化的时空特征,选用坡向、坡度变率、地形起伏度、地形位指数和土地利用类型分布指数对土地利用的地形梯度分布特征和变化过程进行分析。结果表明:1)2000—2016年,榆次区建设用地主要向西北方向扩张,主要分布在地形起伏度30m、坡度变率2°、阳坡和半阳坡及地形位为1～3级的地区。土地利用以建设用地、耕地和未利用地为主,其中耕地所占面积最大,2000年、2008年和2016年的平均比例为46.91%。2000—2008年建设用地面积增加43.07 km2,未利用地面积减少37.33 km2; 2008—2016年未利用地面积减少221.00 km2,而耕地面积和建设用地面积分别增加170.61 km2和37.36 km2。2)在坡度变率、地形起伏度和地形位梯度上,建设用地、耕地和水域主要分布于低梯度带,而林地和未利用地分布于中高梯度带;建设用地和耕地在平地、阳坡和半阳坡呈分布优势,林地在阴坡和半阴坡具有分布优势,而未利用地的优势分布区为阳坡和半阳坡;2000—2016年耕地的主要分布区向地形起伏度30 m、坡度变率为2°～15°、地形位为4～11级的区域扩张。榆次区土地利用变化地形梯度差异明显,地形因素、人类活动、政策因素、交通和区位为其主导因素。该研究结果为区域城镇化过程中的土地合理规划利用提供科学依据,为生态环境治理提供决策支持。

Land use change with topographic gradients in the Yuci District rapid urbanization area

The influence of topographic factors on land use change is significant for land use and cover change research. In order to explore the characteristics of land use change with different topographic gradients, in this study, ASTER GDEM data and remote sensing data of Yuci District in 2000, 2008, and 2016 were used to analyze the spatio-temporal characteristics of land use change from 2000 to 2016. The distribution characteristics and varying development of each land use type with aspect gradient, slope change rate, landform relief, and terrain niche were analyzed. The results showed the following: 1) from 2000 to 2016, construction land expanded primarily to the northwest and was mainly distributed in areas with a landform relief less than 30 m, a slope change rate less than 2°, a sunny slope or semi-sunny slope, and a terrain niche grade area of 1-3. The land uses of Yuci District were mainly construction, crop land, and unused land, which accounted for more than 93% of the research area. The crop land area is the largest, accounting for an average 46.91% of total land area in 2000, 2008, and 2016. The land use change was characterized by a decrease in unused land area and an increase in crop and construction land areas. The construction land area increased by 43.07 km², while the unused land area decreased by 37.33 km² from 2000 to 2008. However, from 2008 to 2016, the unused land area decreased by 221.00 km², while the crop and construction land areas increased by 170.61 km² and 37.36 km², respectively. 2) Construction land, crop land, and water were mainly distributed on low gradients of landform relief, slope change rate, and terrain niche. Conversely, forest land and unused land were mainly distri­buted on middle and high gradients of the three topographic factors. The construction land and crop land was predominantly distri­buted on flat land, with sunny or semi-sunny slopes, while forest land was predominantly distributed along shady and semi-shady slopes. The distribution of unused land was predominantly along sunny and semi-sunny slopes. From 2000 to 2016, the main distribution area of crop land gradually expanded to areas with a landform relief greater than 30 m, a slope change rate of 2°-15°, and a terrain niche of 4-7 grade area. There were evident differences in the topographic gradient of land use change as a result of topographic factors, human activity, policy factors, transportation, and location. Therefore, this study provides a scientific basis for rational planning and utilization of land in the process of regional urbanization and decision support for ecological environment management.