Spatial characteristics of cultivated land quality, driving forces and enhancement policies on the Tibetan Plateau: A case study of Qushui County, Tibet, China

Cultivated land quality (CLQ) is the inherent capacity of cultivated land to function in productive activities and depends on soil properties, management practices and landscape patterns. The aim of this study was to evaluate the current status of CLQ and landscape patterns in the Qushui County and assess the influence of landscape patterns on CLQ. Consequently, complementary policies are recommended to improve CLQ on the Tibetan Plateau. The results indicated that the soil in Qushui County was classified as sandy loam, with a bulk density, effective soil thickness, pH, cation exchangeable capacity, organic matter, total nitrogen, available phosphorus and available potassium of 1.41 g cm -3 , 63.03 cm, 7.58, 8.82 cmol kg -1 , 18.27 g kg -1 , 1.14 g kg -1 , 15.82 mg kg -1 and 85.53 mg kg -1 , respectively. Elevation and soil type were key factors influencing CLQ. Consequently, the optimum quality of cultivated land was observed at low elevations, with fluvo-aquic soils and cold brown calcic soils. These effects were driven mainly by human activities, including irrigation, drainage measures and protected forests on farmland. Landscape patterns, which are products of human activity, constitute another important factor affecting CLQ. The results confirmed that CLQ had significant positive spatial relationships with the largest patch index (LPI), mean patch area (AREA_MN) and aggregation index (AI), whereas it had significant negative spatial relationships with the mean shape index (SHAPE_MN) and fractal dimension index (FRAC_MN) (P≤0.01). Additionally, the influences of the area–edge, shape and aggregation indices on the CLQ were either independent or interactive, with interactions being dominant. These results confirm that CLQ depends on its area and regular shape. The government should guide farmers to optimize cultivated landscapes through systematic management, leading to an improvement in CLQ.