Information extraction and characteristic analysis of cultivated land abandonment in karst rocky desertification mountainous areas based on time-series vegetation index

Due to the influence of rocky desertification, the phenomenon of abandoned farmland is serious in karst mountainous areas. The accelerated urbanization process, the transfer of rural labor force, and the obstruction of agricultural mechanization have aggravated the abandonment of cultivated land. Curbing the large-scale abandonment of cultivated land is of great significance to regional food security and sustainable agricultural development. Taking a typical karst rocky desertification mountainous area as an example, using Sentinel-2 A remote sensing images, the NDVI time series change detection coupling joint detection method was used to extract the abandoned land in Guanling County from 2019 to 2022, and its desertification degree and spatial heterogeneity were analyzed. The results show that: (1) The OA of the identification results of abandoned land and non-abandoned land from 2019 to 2022 is 0.86, and the Kappa coefficient is 70%, with good identification effect; (2) The abandoned area in Guanling County continued to increase from 2019 to 2022, but most of them were abandoned for two to three years, and a few were abandoned for four years. There were phenomena of recultivation and sudden abandonment of farmland; (3) Abandonment mostly occurred under conditions of no obvious desertification, mild desertification and moderate desertification, and the abandonment rate gradually decreased with the increase of desertification; (4) The abandoned land in Guanling County was mainly distributed in the direction of "northwest-southeast", with high fragmentation, low spatial aggregation and strong heterogeneity. The study extracted information on abandoned farmland in karst desertification mountainous areas to provide a data basis for food security and protection of farmland quantity.