Permanent prime farmland demarcation in city periphery in peninsula hill areas: A case of Haiyang City in Shandong Province

The red lines of prime farmlands constitute the top priority of the "Tri-Line" demarcation of general land use planning. The demarcation of permanent prime farmlands in city periphery has been of great significance for controlling city unlimited sprawl, stabilizing farmland area and ensuring food security of the country. Using Haiyang City in Shandong Province as a case study, this study developed a land planning strategy for the study area based on the "Tri-Line"-coordinating demarcation process. The study adopted procedures of ecological priority, strict construction land evidence, positive demarcation of high-quality cultivated land and market resources allocation to integrate ecological safety network, suitable evaluation of construction land and comprehensive evaluation of cultivated land to demarcate the permanent prime farmland in the study area. To comprehensively evaluate the cultivated land quality, the land evaluation and site assessment (LESA) method was improved, and ArcGIS was used to analyze spatial distribution of cultivated land patch. The results showed that the area of cultivated lands in ecological safety network was 12.11 hm², and those in the priority construction region and important construction region was 154.99 hm², both were not suitable for permanent prime farmland. The cultivated land in the city periphery was divided into 4 grades based on comprehensive quality scores. The priority area and suitable area were designated as permanent prime farmland, where the natural quality and site condition were superior. Then the controlled area and reserved area were not included in this division. About 458.05 hm²land was in the priority region, of which 427.82 hm² of the cultivated land was classified as permanent prime farmland. About 771.83 hm² land was classified as suitable area, of which 500.67 hm² was permanent prime farmland. After demarcation, the area of permanent prime farmland around Haiyang City was 1 305.22 hm², of which newly cultivated land formed 928.49 hm², accounting for 60.26% of the total cultivated land around the city. Overall, permanent prime farmland protection rate increased by 42.66%. The average use index of cultivated land in permanent prime farmland (9.04) was higher than that of cultivated land in the whole city (9.56), and the slope of the permanent prime farmland was less than 15°. 4) The layout of ecological security land, permanent prime farmland and construction land around the city was more optimized in favor of the orderly development of the city and the sustainable use of the land. In summary, based on the improved LESA evaluation method and comprehensive consideration of layout space of ecological security land, permanent prime farmland and construction land, the study enriched the demarcation method of permanent prime farmlands and achieved permanent prime farmland demarcation in Haiyang City. At the same time, the results of the study were practicable and provided the scientific basis for the protection of permanent prime farmlands and the application of "Tri-Line" demarcation in general land use planning.