Spatial conflict and zoning optimization of cultivated land and orchard land in the hilly and mountainous areas based on coupling of topographic gradient and cultivated land quality

Spatial conflict between cultivated and orchard land can refer to the cultivated-orchard land. It is often required for food security, ecological sustainability, and rural development in the hilly and mountainous regions. Driven by economic incentives, the orchards can encroach onto high-quality cultivated landin plains, described as "orchard moving downhill". The "cultivated land moving uphill" was termed as the simultaneous reclamation of ecologically vulnerable steep slopes (>25°) for the compensatory cultivation. There was also substantial environmental degradation, including the fertile soil loss, water erosion, and ecosystem deterioration. The field test was carried out in Ganzhou City, a typical hilly and mountainous area in southern Jiangxi Province, China. The data was collected from the multi-temporal land use (2009–2023), digital elevation model (DEM), and cultivated land quality classification. An integrated "terrain niche index (TPI)–cultivated land suitability" coupling model was developed to combine the spatial analysis techniques—including kernel density estimation, spatial autocorrelation (Global Moran’s I and Getis–Ord Gi*). An entropy-weighted TOPSIS was utilized to assess the land quality. A systematic investigation was also made to explore the mechanisms of the Farmland-to-Orchard conversion conflict from the dual perspectives of terrain gradient and cultivated landquality. The results demonstrate that: (1) The total area of the Farmland-to-Orchard conversion in Ganzhou reached 20 513.81 hm², accounting for 4.06% of the total. There was a significant and persistent transformation of agricultural land. Spatially, a distinct pattern was the "denser in the east and sparser in the west, with the higher rates in the south and the lower in the north". Ruijin City and Xunwu County were identified as the critical conflict hotspots. There was a strong correlation with the intensive cultivation of the high-value crops, such as the navel oranges and tea oil camellia. (2) The conversion exhibited a strong constraint of the terrain gradient, which predominantly occurred in the flat and gently sloping areas—specifically, valley plains (9 614.69 hm², 46.87%) and low-mountain gentle slopes (9 085.67 hm², 44.29%). (3) Quality analysis revealed that the converted land was predominantly high-quality farmland, where the Grades 1-3 land constituted 17 030.50 hm² (80.7% of total conversion). The conversion was selectively targeted to accelerate the loss of the prime agricultural land. (4) Conflict analysis was carried out using a matrix integrating terrain gradient zones and cultivated land quality grades. There were the strong-conflict zones with the 15 217.75 hm² (74.18% of total converted area), which were concentrated primarily in valley plains with the superior farming conditions. Medium-conflict zones accounted for 3 718.88 hm² (18.13%), located mainly on the gentle slopes with medium-quality land. The conflict of Farmland-to-Orchard conversion occurred predominantly in the areas with the gentler topography and higher-quality soil. A differentiated regulatory strategy was proposed using dual terrain-quality thresholds. A scientific framework was offered to balance the cultivated landprotection with the characteristic forest and fruit industries in southern China's hilly and mountainous regions. A differentiated regulation strategy was proposed under the dual threshold constraint of 'terrain-quality'. The finding can also provide a scientific paradigm to protect the cultivated land and the development of characteristic forest and fruit industry in the hilly and mountainous areas of southern China.