**1. Introduction**

Healthy cultivated land use systems have functional continuity [1]. The function of cultivated land refers to the ability of cultivated land to provide products and services, and it evolves in a complex process from a single function into multiple coordinated functions [2,3]. The multifunctionality of cultivated land has become an essential attribute of its use [3].

**Citation:** Gao, J.; Zhu, Y.; Zhao, R.; Sui, H. The Use of Cultivated Land for Multiple Functions in Major Grain-Producing Areas in Northeast China: Spatial-Temporal Pattern and Driving Forces. *Land* **2022**, *11*, 1476. https://doi.org/10.3390/ land11091476

Academic Editors: Yongsheng Wang, Qi Wen, Dazhuan Ge and Bangbang Zhang

Received: 29 July 2022 Accepted: 2 September 2022 Published: 3 September 2022

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Cultivated land has traditional production and service functions necessary for human society [4]. With the development of the economy and technology, cultivated land is now not limited to traditional functions and has transitioned from having a single function to multiple functions [3,5]. As a basic resource and material guarantee for human survival, the multiple functions of cultivated land include its use to provide products and services necessary for human survival and development [6]. These functions of cultivated land include production functions, such as providing food, vegetables, and oil; ecological functions, such as regulating the atmosphere and maintaining water and soil; social functions, such as ensuring farmers' livelihood and maintaining national food security; cultural functions, such as providing farming landscapes and spatial landscapes; and non-commercial functions, such as for building space reserves and other space-bearing reserve functions [7]. Thus, the utilization of cultivated land has led to its gradual expansion from production functions to social security functions and ecological functions [3,5,7]. Cultivated land is an irreplaceable basic resource needed for human survival and development and a core element contributing to food security and regional sustainability [8–10]. Therefore, the multifunctional use of cultivated land is an important concept that must be considered when assessing reginal cultivated land use changes and their effects on the sustainable use of cultivated land. Thus, the coupling coordination level of cultivated land used for multiple functions should be determined, as it can provide a feasible reference for optimizing the efficiency of the regional utilization of cultivated land [11].

The multiple functions of cultivated land start from its use for agricultural functions [12–15]. The Global Land Project (GLP) takes the multifunctionality of land as the basic framework with which to analyze the coupling of natural, ecological, social, and economic systems [16]. The multiple functions of cultivated land have been widely considered by scholars. The existing research on this concept mainly focus on the assessment of multiple functions of cultivated land [1,3,17–19]. The assessment of the multiple functions of cultivated land has been widely discussed since the implementation of the Land Use and Land Cover Change (LULL) program [3,20]. The current studies focusing on the assessment of the multiple functions of cultivated land concentrate on two major aspects: the assessment of each land use function individually and the comprehensive assessment of the multiple functions of cultivated land. Studies focused on the assessment of individual land use functions mainly aim to quantify each function of cultivated land, such as its production, ecological, social, or economic functions [21–25]. In the research on comprehensive cultivated land multifunction assessment, a growing number of studies have obtained the total intensity level of different function of cultivated land by summing the value of each cultivated land function [19,26] and some studies have analyzed the driving forces behind the use of cultivated land for multiple functions [3,27,28].

However, the emphasis of most studies was often on a single function or the impact issues of separate functions. While the comprehensive function of cultivated land is the result of coupling the coordinated development of the multiple functions, the multifunctional coupling coordination degree of cultivated land has rarely been reported on, much less the spatial-temporal pattern and driving forces of the coupling coordination degree of cultivated land used for multiple functions. Thus, our understanding of the multiple functions of cultivated land is poor. Furthermore, long-term studies can be used to examine the evolution mechanism of cultivated land used for multiple functions and offer a policy reference to increase the use of cultivated land for multiple functions, an area which lacks attention. As it stands, in the research of cultivated land multifunctionality, less focus has been provided to major grain-producing areas. In order to improve the shortcomings of the existing research, a better understanding of the spatial-temporal pattern of cultivated land used for multiple functions in major grain-producing areas is needed, and the spatial-temporal pattern, driving forces, and influencing mechanisms of the multifunctional coupling coordination degree of cultivated land need to be identified as well. Through this, effective policies can be promoted to improve the use of cultivated land to achieve the goal of sustainable cultivated land use, especially in the major grain-producing areas.

As an important grain base, northeast China is a major grain-producing area, shouldering the responsibility of ensuring national food security. However, in face of the challenges of cultivated land degradation [29] and reduced agricultural production efficiency [30], the sustainable use of cultivated land in northeast China is now seriously threatened. Thus, based on the main functional positioning of northeast China as a major grain-producing area, identifying the spatial-temporal evolution of the multifunctional coupling coordination degree of cultivated land is of great importance in order to take full advantage of cultivated land resources, maximize cultivated land utilization efficiency and yield, ensure ecological security, and maintain social stability in northeast China. Additionally, it is of strategic significance for ensuring the national food security of China.

Considering the research gaps highlighted above and the strategic positioning of the major grain-producing areas in northeast China as a national breadbasket, this study used Heilongjiang province, Jilin province, and Liaoning province as its research area to analyze the spatial-temporal pattern of cultivated land used for multiple functions, including its production, social, and ecological functions; assess the multifunctional coupling coordination degree of cultivated land; identify the spatial-temporal pattern trend and driving forces of the multifunctional coupling coordination degree of cultivated land; and finally put forward measures for the optimization of the usage of cultivated land for multiple functions. The reminder of this paper is structured as follows. Section 2 describes the materials and methods. The Comprehensive Index Model is used to calculate the evaluation value of cultivated land functions. The Coupling Coordination Degree Model is used to assess the multifunction coupling coordination degree of cultivated land. Geodetector is used to explore the driving forces behind the evolution of the multifunctional coupling coordination degree of cultivated land. Section 3 discusses the empirical results of the models. Sections 4 and 5 present the discussion and conclusions of this study, respectively.
