贵州中部岩溶山区坡耕地时空演变特征及驱动因素分析

坡耕地是中国西南岩溶山区粮食安全和生态保护的重要保障,深入研究其时空演变特征具有重要意义。该研究选用2004－2020年高精度遥感影像和数字高程模型,从地形位指数、核密度、耕地利用动态指标分析典型岩溶山区普定县坡耕地时空演变在不同地形位等级上的响应,并对坡耕地演变的驱动机制进行探究。结果表明：1）2004－2020年,研究区坡耕地在空间上呈"东南多、东北少、西部较少"的分布特征。坡耕地分3个阶段收缩：急剧收缩阶段（2004－2009年）高地形位坡耕地撂荒收缩速度最快,缓慢收缩阶段（2009－2015年）中地形位坡耕地收缩速度最快,加速收缩阶段（2015－2020年）低地形位坡耕地收缩速度最快;2）第一级、第三级地形位范围内坡耕地变化面积最大,高地形位劣质坡耕地向林草地转型占总体转型面积的69.67%,低地形位坡耕地向园地及建设用地转型占总体转型面积的38.14%;3）坡耕地演变由陡坡向缓坡转移、由高海拔向低海拔转移,聚集度下降,高地形位坡耕地转型提高区域生态效益,中、低地形位坡耕地转型实现区域生态经济双赢效益;4）自然地理环境是坡耕地时空演变的基础支撑,社会经济是主导因素,政策是外在拉力,不同梯度地形位坡耕地影响的主导因素差异明显。研究结果可为西南岩溶山区不同地形土地利用优化及生态保护提供科学参考。

Spatiotemporal evolution and driving factors of slope cultivated land in karst mountainous areas of central Guizhou Province, China

Slope cultivated land has been the major grain production base to ensure food security and ecological protection in the mountainous karst areas of southwest China. It is necessary to clarify the spatiotemporal evolution characteristics of the slop cultivated land at present. In this study, a quantitative analysis was performed on the spatiotemporal evolution of slope cultivated land in different terrain gradients using high-precision remote sensing images and Digital Elevation Models (DEM) from 2004 to 2020. Puding County in the typical karst mountainous areas of central Guizhou Province, China was selected as the study area. The driving mechanism was proposed for the slope cultivated land evolution from the terrain niche index, kernel density, and dynamic indicators of cultivated utilization. The results show that: 1) There were the typical characteristics of "more in the southeast and less in the northeast" for the slope cultivated land in the study area from 2004 to 2020. The distribution of slope cultivated land in 2020 mainly belonged to the low-density area of kernel density, followed by the medium-density area, while the high-density area occupied an ever-decreasing small proportion of the area. 2) The contraction of slope cultivated land was classified into three stages: the sharp contraction (2004-2009) with the highest abandonment rate of high terrain slope cultivated land, the slow contraction (2009-2015) with the highest contraction speed of medium terrain slope cultivated land, and the accelerated contraction (2015-2020) with the highest contraction speed of low terrain slope cultivated land. There were spatiotemporal differences in the different terrain gradient ranges in the slope cultivated land. 3) There was the largest area of slope cultivated land in the first and third terrain gradient ranges. 69.67% of the overall transformation area was converted from the low-quality slope cultivated land in the high terrain into forest and grassland. 38.14% of the overall transformation area was shifted from the slope cultivated land with the excellent production conditions in the low terrain to the garden and construction land. 4) The slope cultivated land evolved from the steep to the gentle slope, and from the high to low elevation, indicating the decrease in the aggregation degree. The slope cultivated land in the high terrain was also transformed to improve the regional ecological benefits. The slope cultivated land in the middle and low terrain greatly contributed to the regional ecological-economic benefits. 5) The multiple factors were attributed to the spatiotemporal evolution of slope cultivated land. Specifically, the natural and geographical environment was the basic support, while the social and economic factors were the leading factors, and the policy factors were the external pull. The path of "agricultural restructuring - slope cultivated land transformation" was attributed to the evolution of slope cultivated land in the low terrain gradient, while the "policy-driven - labor migration - slope cultivated land abandonment" was for the middle terrain gradient, and the "resource endowment - slope cultivated land transformation" was for the high terrain. There were different dominant influencing factors of slope cultivated land in the different gradient terrain. The finding can also provide a scientific reference for land use optimization and ecological protection in the mountainous karst areas in southwest China.