Spatial differentiation characteristics of cultivated land multifunctional value under urban-rural gradient

Abstract: A long-term underestimate of cultivated land has posed serious challenges to sustainable development in China. Particularly, the cost of occupying cultivated land is relatively low to threaten the future national food and ecological security in urban expansion, although the government has implemented strict cultivated land protection policies (CLPP). Therefore, the spatial differentiation of multi-functional cultivated land can contribute to improving the CLPP during this time. This study aims to explore the differentiation law of multi-function value in the cultivated land using the remote sensing images and statistics Yearbook of Shijiazhuang City, Hebei Province, China, in 2018. The specific values were also calculated, including the production function in grid-scale farmland, ecological maintenance, and social security function. A gradient analysis was introduced to determine the value differentiation of three functional unit areas. A cascade ring and sampling were also taken to the city center as the origin, where the gradient analysis was conducted on the change of values. The results showed that: 1) There was a trend of "U"-decline in the functional value of cultivated land in the study area in 2018. The peak value was found in the fourth "U" -shaped trend of inverted land under the urban-rural integration. Specifically, the total value of the unit area was 2318 669 300 Yuan. It infers that the rapid urbanization made the urban community to be the center of education, medical care, and economy. The population gradually gathered to the radiation areas of the first and second rings in the city center, where the total value of one ring per unit area was the lowest at 1,0070,764,7 million Yuan. The functional value of 1-4 loop increased, whereas, that of 7-10 loop decreased significantly. Among them, the ecological maintenance function made the largest contribution rate to the total functional value of arable land, with more than 49%. The social security function accounted for about 30% of the total value. The material production function was the lowest value, representing about 19%. The data demonstrated that the non-productive function value in the cultivated land was much higher than that of the production function. 2) Cascade ring analysis found that the highest value appeared in Ring 1-4, namely 10-40km away from the city center. The material production function was found in the fourth ring, while that in the 6th-10 ring decreased significantly, where the unit output value of 463.5446 million yuan, and the peak of 122.413 million Yuan. The largest value of social security function was dominated by location factors, where the first area value of 847 2276 million Yuan. 3) Strip analysis was found that the functional value of cultivated land in the north and south belt presented an inverted U-type trend of "rising and decreasing", and the ecological maintenance function presented a symmetrical "M" -shape. The value of social security function in the east-west section changed significantly in the west, whereas, the value of ecological maintenance function changed dramatically in the eastern part of the study area. Consequently, the findings can provide scientific suggestions for the planned promotion of multi-functional land use and the optimal allocation of cultivated land resources.