Abstract: Exploring land use changes and their terrain gradient effects can provide a scientific basis for the rational planning and sustainable utilization of land resources. With the Red River Basin in Yunnan Province as the research area, we used land use data of 2015 and 2020, crop data from 2017 to 2020, digital elevation model (DEM) data, distribution index and terrain position index to investigate land use and crop cultivation changes as well as their terrain gradient effects, and further conducted functional zoning. Our results showed that forests dominated the basin, accounting for more than 62.8% of the total area. From 2015 to 2020, the areas of water and built-up land increased by 118.55 km² and 69.68 km², respectively, while other land types decreased. Between 2017 and 2020, maize had the largest planting area and showed an increasing trend, expanding by 270.30 km² in total, the planting areas of single cropping rice and sugarcane fluctuated, whereas rapeseed planting decreased. Cultivated land, built-up land, and water bodies were concentrated at low terrain positions (level of terrain position index was 1-3), whereas forests were concentrated at high terrain positions (level of terrain position index was 8-10), grasslands occurred predominantly at mid-to-low positions (level of terrain position index was 1-5). Single-cropping rice tended to expand toward higher terrain positions. Maize was distributed relatively evenly at mid positions. Sugarcane and rapeseed were concentrated at mid and low terrain positions, respectively. The basin could be divided into four functional zones: urban-agricultural coordinated development zone, transitional agro-pastoral composite zone, ecological forestry and steep-slope management zone, and natural ecological conservation zone. The findings would provide a scientific basis for regional land use planning and agricultural structural adjustment.

Key words: land use, crop planting, terrain position, functional zoning, Red River Basin of Yunnan Province