Spatio-temporal variation of cultivated land in Hebei Province of China using geomorphic regionalization during 2009-2018

Geomorphology is the science of landforms, including their origin, form, evolution and distribution across the physical landscape. There is also a decisive role in the quality of cultivated land, due to the distribution of surface water and heat subjected to the geomorphology. This study aims to grasp the inflow and outflow characteristics of cultivated land in the different geomorphic units in Hebei Province of China during 2009-2018. An analysis was then made to determine the relationship between the quantity, quality, climate, and landform. A systematic evaluation was also made to provide a strong reference for the decision-making on the policy of cultivated land protection. The data of land use was collected in 2009, 2012, 2015 and 2018, such as the geomorphic division, precipitation, temperature, and Digital Elevation Model. The GIS spatial analysis, single land type flow analysis, and index models were used to determine the temporal and spatial changes of cultivated land, particularly from the perspective of geomorphic division in three periods of 2009-2012, 2012-2015, and 2015-2018. The results showed that: 1) There was a stable area of cultivated land in the study area in recent ten years, indicating the low dynamic degree and relative changing rate of cultivated land. Specifically, the cultivated land decreased by 29 100 hm2, with an average annual decrease of 3 200 hm2. The superposition analysis was then performed on the inflow and outflow of cultivated land. The geomorphological zoning demonstrated that there was a great decrease in the area of cultivated land in the plains and intermountain basins, whereas, an increase in the hills, mountains and plateaus. 2) The average elevation of cultivated land increased significantly, where the center of cultivated land was moved northward. A digital elevation model was also used for the spatial analysis of the inflow and outflow of cultivated land in 2009-2012, 2012-2015, and 2015-2018. It was found that the average altitude was 321.89, 120.25, and 102.78 m higher than that of the outflow cultivated land. The center of gravity for the inflow of cultivated land was moved 78.19, 38.05, and 18.06 km to the northwest, northeast, and north, respectively, compared with the outflow. 3) The cultivated land was transferred to the areas with less precipitation and lower temperature. The spatial analysis was made on the inflow and outflow cultivated land using the average precipitation data. Among them, the average precipitation of inflow cultivated land was higher than that of outflow. The area of cultivated land with precipitation of less than 400 mm increased by 15 700 hm2. By contrast, the area with precipitation over 400 mm was reduced by 44 800 hm2. In addition, the average temperature of inflow cultivated land was lower than that of the outflow. The area of cultivated land with an average temperature greater than 8 °C decreased by 50 600 hm2, whereas, the area with the average temperature less than 8 °C increased by 21 500 hm2. 4) The flow direction of a single land type showed that the unused land was the main source of cultivated land inflow. The cultivated land outflow was mainly shifted to the construction land, indicating the largest village construction land. Therefore, the high-quality cultivated land with the inferior one can be expected to protect the cultivated land resources during this time. Strong support can be made to promote the requisition-compensation of cultivated land and the subsequent supervision. As such, the high-quality arable land was occupied in the plain areas, whereas, the unsuitable land was reclaimed in the mountainous, hilly, and plateau areas. The finding can provide a strong reference for the trinity protection of cultivated land quantity, quality, and ecology.