Control and management of cropland regionalization in Fujian Province of China using multi-functional evaluation and trade-off/synergy relationships

Cropland is one of the most important resources in a complex ecosystem with the highest degree of human dependence, in order to ensure the regional food and ecological security for the better settlement environment. The coordinated development can be expected to promote in the multi-functions of cropland for the scientific protection and rational utilization of cropland. Therefore, it is very necessary to scientifically evaluate the spatiotemporal changes of multi-functions of cropland, and to clarify the change of trade-off and synergy among various functions of cropland, due to the natural supply and the demand of human society. Taking Fujian Province in southeastern China as an example, this study aims to construct a performance metrics, according to four dimensions of cropland production, ecological, social, and landscape functions. The multi-functional level of cropland was evaluated on the county scale. The comprehensive analysis was introduced to evaluate the multi-functions of cropland, and then to explore the spatial-temporal variation from 2005 to 2020. Pearson product-moment correlation coefficient was selected to analyze the trade-off and synergy relationships among the functions of each dimension. The results showed that: 1) The multi-functional level of cropland decreased slightly in the most areas. Specifically, the high-value areas were concentrated in the eastern and western regions, with the superior productive and ecological function of cropland. The higher ability was found to guarantee the living and employment of farmers. Among them, the production function showed an upward trend, while the ecological function decreased slightly. Both social and landscape functions were improved significantly. The spatial change of social function was weakened from the mountain to the coastal area, whereas, there was the strong spatial change of landscape function. 2) Synergy relationships were dominated among cropland multi-functions. Only the production-ecological and production-landscape function showed the synergy relationship in more than 50% of the areas. The proportion of grid quantity with the trade-off relationship was ranked in the descending order of the ecological-social, production-social, social-landscape, and ecological-landscape function. A spatial heterogeneity was observed in the trade-off and synergy relationship of each function combination. 3) The present condition of cropland was used to determine the characteristics of agricultural production in the different regions. The single function of cultivated land was combined with the trade-off between different functions. The cropland functional areas were divided into four types, including the superiority protection area (38.52%), strict control area (36.71%), remediation area (6.98%), and transition or exit area (17.79%). Some differentiated management and control suggestions were proposed as well. The superiority protection areas were distributed mainly in the eastern and western regions, while the strict control areas were distributed mainly in the coastal areas of northern and southern regions, and the remediation areas were in the Zhangzhou region of Southern regions, as well as the transition or exit areas were scattered throughout the cities. The findings can provide an important decision-making support to protect the cropland resources. The coordinated development can be expected to promote the multi-functions of cropland for the high efficiency of cropland land use.