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.