1. Introduction
Rapid urbanization and economic development have resulted in a series of problems, including soil pollution, land degradation, and low land-use efficiency [
1,
2], which have a significant impact on the land and the environment [
3,
4]. Furthermore, sustainable land use and urban development pose a considerable challenge [
5,
6]. Given that land use is an artificial way of adjusting the land surface, it plays a vital role in the shaping of ecosystem functions [
3]. Thus, many studies on land-use changes, driving mechanisms, and scenario simulations have been conducted [
7,
8,
9].
With continuous economic and social development, different countries have explored and formed various types of spatial planning systems in the process of urbanization and industrialization. Since China’s experience of problems such as human–land contradiction have become prominent, the urban area is rapidly expanding, the imbalance in regional development has intensified, and unreasonable land-use impedes the improvement of land-use efficiency and is not conducive to resource-intensive use and sustainable development [
10]. Its territorial spatial pattern is also changing rapidly. In the process, China has also gradually explored a variety of plans that fit the local situation. However, multiple management problems and a lack of overall space control have been experienced. To address these problems, the state implemented institutional reforms and decided to build the National Territory Spatial Planning System to promote the intensive use of land resources and sustainable development [
11,
12,
13,
14]. Making spatial planning in line with national conditions has become the focus of the current planning task. The optimization of land-use structure, as a part of the spatial planning system, balances social, economic, and ecological development goals, minimizes the conflicts between land uses, and further optimizes the use of space [
15]. Optimizing the structure of land use and realizing the intensive use of land is vital to regional sustainable development [
2].
The theory, method, and research scale of space optimization have attracted widespread attention. Koomen et al. [
16] explored the supporting and guiding role of land-use change patterns for spatial planning based on land-use patterns in macro-planning policies. Todes [
17] studied the use of spatial planning to solve decentralized problems in urban development in Johannesburg, South Africa. Studies in many countries mainly focus on the application of and relationship between land use and spatial planning. China’s research on land-use optimization and its application in planning started relatively late. In recent years, the research results have been enriched, and land-use allocation and optimization and territorial spatial function zoning have been gradually developed and innovated. Several scholars have conducted studies on land use to achieve economic, ecological, economic–ecological, and other goals [
18,
19]. Their research objects include not only large-scale cities (such as urban agglomerations), semi-arid areas, and typical watersheds, but also the administrative scale of provinces, cities, and counties [
20]. It also combines ecological functions and landscape patterns for research [
21,
22]. An increasing number of optimization methods have been developed with the deepening of study, including multi-objective programming, cellular automata (CA), and gray linear programming models [
23]. Although there are various research methods of land-use structure optimization, most of them are single-model methods, especially in the spatial planning system, which has not formed a systematic framework and cannot provide a unified and applicable method system for the construction of spatial planning. Therefore, in the process of implementing spatial planning, the optimization of the land use structure in various regions increasingly requires a unified analysis process to identify the problems existing in the current land use, and then put forward suggestions on the critical directions of land use.
This study explores an analytical framework (
Figure 1) to provide methodological support for understanding the existing problems in spatial planning land use and further optimizing critical directions. This analytical framework explores the characteristics and problems of current land use through the analysis of the current situation of regional land use. The framework analyzes the change rate of land use of various types through the dynamic degree of land use and uses the comprehensive index of land use to explore the degree of land use. At the same time, the intensive utilization degree, development potential and remediation potential of land use are obtained through potential analysis. Moreover, it uses the LUCC simulation model to simulate the land-use change. According to the existing research [
24], the LUCC simulation model is divided into four categories: change description model, quantity prediction model, process-based simulation model, and hybrid simulation model. Researchers can choose different potential evaluation methods and LUCC simulation models according to their own needs. Based on this, the critical directions of regional land use are clarified. The analytical framework helps to better understand the mechanism and future development trend of regional land use change, to clarify the direction of critical use, and to provide scientific support for the adjustment of land use structure.
To this end, the study selects Changzhi City, Shanxi Province as a case to explore the feasibility of this framework. The purpose of the research is: (1) to analyze the current situation and structure of land use in Changzhi City; (2) to evaluate the potential of land use in Changzhi, and to discuss the problems of land use in Changzhi; (3) to explore the future land use situation of Changzhi City, and to propose critical directions for future land use. The research is beneficial to local ecological protection and urban development, as well as to optimizing land use. Utilization patterns and strengthening regional land-use efficiency can provide new ideas for optimizing land-use structures in spatial planning [
25,
26,
27].
4. Discussion
4.1. Overall Spatial Pattern of Changzhi City
According to the current state of the land and space structure of Changzhi City, the development and protection of land and space in Changzhi City present an overall pattern of “one center, one circle, two rivers, and three districts.” “One center” means one city and four districts. “One center” is the growth pole of urban development and the core of building a central regional city in the southeast region of Shanxi Province and participating in regional competition and cooperation. “One circle,” namely, the Changzhi metropolitan area, is the main body of building a central regional city in the southeast of Shanxi Province and the main area of population and urban economic agglomeration. “Two rivers” refer to the ecological corridors of the two major water systems of the Qin River and the Zhuozhang River that strengthen the river basin governance and enhance ecological functions. “Three districts” refer to the two environmental barrier areas of Taihang Mountain and Taiyue Mountain and the agricultural area of the Zhanghe River Valley Basin.
The main function area plan is divided into the national agricultural product main production, provincial agricultural product main production, regional urbanization development, and provincial critical ecological function areas. The main agricultural production areas are areas that have good agricultural production conditions and provide agricultural products as the main function. The main national agricultural production areas include Tunliu District, Zhangzi County, Xiangyuan County, and Qin County, and the main provincial agricultural production areas are in Wuxiang County, and these areas have large, cultivated land and grain output, which ensure the supply of grain and other agricultural products. The provincial-level urbanization development zones mainly include Luzhou District, Lucheng District, and Shangdang District. These areas are densely populated and have a high development intensity, a large construction land, and a relatively developed economy. The critical provincial ecological function areas include Pingshun County, Licheng County, Huguan County, and Qinyuan County. The forest land and grassland area are relatively large, and the biodiversity and the ecological protection are good.
The area of the ecological red line designated by Changzhi City accounts for approximately 19% of the entire city, which is mainly distributed in the western region of Qinyuan County, the northwest of Qinxian County, Pingshun County, and Huguan County, and the junction of Licheng County, Wuxiang County, and Xiangyuan County. Among them, the core areas of nature reserves are mainly distributed in the Shanxi Lingkong Mountain National Nature Reserve in the west of Qinyuan County, the Shanxi Mianshan Provincial Nature Reserve, the Shanxi Zhuozhang River, the Provincial Nature Reserve in Qinxian County, and the Shanxi Central Mountain Provincial Nature Reserve in Licheng County. Permanent basic cultivated land is designated in the whole city, accounting for approximately 21% of the entire city and mainly distributed in Tunliu District, Changzi County, Xiangyuan County, Qin County, Wuxiang County, and other areas with a large, cultivated land area. The urban development boundary mainly delimits the centralized construction and flexible development zone at the present stage. The urban development boundary delimited by Changzhi City is primarily concentrated in Luzhou District and its junction with surrounding districts and counties and the central area of other counties.
The land use of Changzhi City should focus on the development of urban construction within the scope of “one city and four districts” but pay attention to avoiding basic farmland and nature reserves within the urban area, and do an excellent job in related protection work. It is necessary to combine the planning of main functional areas, give full play to regional advantages, ensure the supply of agricultural products, and pay attention to ecological protection during economic development to form a characteristic regional economy.
4.2. Land Use Problems in Changzhi City
The above analysis indicates that the land use in Changzhi City is dominated by agricultural land, such as forest land, cultivated land, and grassland, and shows apparent spatial distribution characteristics of “forest-cultivation-forest” from west to east. Forest land is mainly distributed in the west, the east, and the northeast, cultivated land is primarily distributed in the middle of Changzhi City. Construction land is primarily distributed in the urban centers of various districts and counties, of which Luzhou District is the most obvious. The area of construction land in Changzhi City is relatively small, reflecting the small scale and urban capacity of the city center of Changzhi. Therefore, the development and construction of the city will still be accelerated in the future. In addition, nearly half of the other land in the city is bare land. Rivers, lakes, and tidal flats account for more than 90% of Waters and water conservancy facilities land. Few other lands have development potential. Intensification should be strengthened in the process of land use to utilize to improve the degree of land utilization. From an overall point of view, the scope of construction land continues to expand to the periphery. As an important development area, “one city and four districts” has the most construction land in Changzhi City and a large amount of cultivated land around the construction land. With continuous deepening, the occupation of cultivated land is inevitable. From 2010 to 2018, the comprehensive degree of land use in Changzhi City showed an increasing trend. Still, the cultivated land with the highest comprehensive degree of land use showed a downward trend, mainly because the reduction of cultivated land significantly reduced its utilization. This phenomenon also indicates that in urban construction and planning, if the land type transformed from cultivated land cannot be fully developed and utilized, it will be unable to provide the equivalent value of its historical use. Therefore, ensuring the amount of cultivated land and completing the conversion between different land types in the specific planning also requires further discussion.
The exploration of the characteristics of land use in Changzhi City reveals that many problems remain in its current land use. First, the amount of cultivated land decreased by a significant amount, and apparent contradiction between people and land. As the population continued to increase, the large decrease trend in cultivated land was not effectively controlled, and the total cultivated land and per capita cultivated land continued to decline. From 2010 to 2018, the city’s population increased by 55,900 annually, while the city’s cultivated land decreased by an average of 2662.48 ha per year; the city’s per capita cultivated land was 0.10 ha, and notable contradictions between human and cultivated land. Second, the land use structure was unreasonable, and it has a weak land ecological environment. The land reclamation rate in Changzhi City is relatively high. In contrast the ratio of forest (fruit) animal husbandry land is relatively small, and the proportion of forest land in the forest is small, the coverage rate of forest and grass vegetation is low, and the land-use structure is not reasonable enough. Thus, the city’s comprehensive land production potential and advantages are not fully utilized; in mountainous and hilly areas, except for some natural forest concentrated areas where the natural vegetation coverage is relatively high, other areas have serious soil erosion and a fragile ecological environment, which affect the land ecological environment of the city. Third, the land use is relatively extensive, and the degree of intensive use is low. Among the used lands, the problems of comprehensive land use and low degree of economy and intensiveness remain. The main manifestations are as follows. First, regarding agricultural land and its utilization, the proportion of low- and medium-yield fields and orchards is relatively large, and the phenomenon of land abandonment is still relatively serious. Second, construction land is still mainly extended by extension, and a certain amount of idle land and inefficient use of stock construction land can be observed within it.
4.3. Suggestions on Critical Directions of Land Use
To shape a high-quality territorial space, promote the modernization of territorial space governance system and governance capabilities on the basis of the premise of coordinating supply and demand, and improve both ecological and economic benefits, the critical directions of land use are clarified on the premise of coordinating supply and demand and aiming at the dual improvement of ecological and economic benefits. Cultivated land, forest land and various construction land are still the focus of future land use. Using the analysis framework to analyze the status quo of land use, potential evaluation and probabilistic evolution reasoning in Changzhi City can provide a reference for the adjustment of land use direction to a certain extent.
Changzhi City has more mountains than plains, and forest land is the primary land type. With the gradual combination of ecological civilization and planning, forest land is expected to remain the main land type in Changzhi City for a long time, and the distribution characteristics show little change. The intensive utilization of construction land in the counties and districts of Changzhi City is low. This finding can be attributed to its low level of urbanization and small economic aggregate, and the land use is basically in the transition stage from extensive to intensive use. In addition, noticeable regional differences exist in the level of intensive use of construction land in Changzhi City. The uneven economic development and different local natural conditions have led to the uneven construction use land in Changzhi City. Luzhou District and Shangdang District, which have high economic development levels, have intensive construction land use. The level is also high. Therefore, the economically underdeveloped regions should be active in their economic development level, learn from the experience of developed areas, and strive to improve the level of intensive use of their construction land. The areas with a high potential for cultivated land resources in Changzhi City are primarily located in Licheng County, Xiangyuan County, and other areas. However, Qinyuan County has a large forest land area and is affected by ecological protection and other planning. The county’s cultivated land development is subject to certain restrictions, so the development potential of its cultivated land reserve resources is low. The rural construction land consolidation potential of Changzhi City is relatively high, and a large room for remediation exists. The rural construction land consolidation potential in Shangdang District is the lowest, and its construction land intensive utilization degree is high, indicating that the level of intensive use of the construction land of Shangdang District is relatively high. Although Luzhou District has a relatively high degree of construction land intensiveness, a large potential space for rural construction land consolidation remains. In future planning, inefficient and idle lands should be integrated, and land use supervision and management should be strengthened.
Overall, the suggestions for adjusting the direction of land use in Changzhi are as follows. First of all, “one city and four districts” should be regarded as critical areas. Among them, Tunliu District, as an area that has just been included in the construction scope of the main urban area, has a considerable amount of arable land, a high conversion probability of arable land, and a large potential space for rural construction land consolidation. Intensive utilization of land is low; however, as a critical development area in the process of urbanization, it should integrate low-efficiency land and idle land within it, and expand the scope of construction land. In addition, the conversion probability of construction land in Tunliu District, which is adjacent to the old city Luzhou District, is higher, which is consistent with the general urban expansion law. However, as the main production area of national agricultural products, the protection of cultivated land is very important. Therefore, in the process of urban expansion, it is necessary to pay attention to the development and utilization of land in Tunliu District and coordinate the protection and development of cultivated land for construction land demand, etc. Secondly, the conversion probability of cultivated land in Licheng County and Xiangyuan County is relatively high, and the development potential of cultivated land reserve resources is large. The existing cultivated land should be further protected, and other land types in the region that can be reclaimed into cultivated land should be developed, expanding the guarantee of food supply. In addition, Xiangyuan County and Changzi County have high potential for rural construction land consolidation, and there are many inefficient and idle land in the region, which can be reclaimed into arable land to provide more guarantee for food security or can be converted into arable land as needed. Other land types will further improve the efficiency of land use. As for Changzi County and Qin County, which have a low degree of construction land intensiveness, in the subsequent adjustment, they should focus on improving their degree of intensification to ensure the effective use of land.
4.4. Deficiencies and Prospects
The research analyzes the land use situation in Changzhi City and puts forward suggestions for the future land use direction, which not only provides scientific support for regional development, but also provides ideas for building a unified land-use optimization analysis process. The research only proposes the general direction of land-use structure in space, but still lacks the prediction and analysis of the quantity of different land use and does not quantify the specific prediction situation. The follow-up should focus on the quantitative prediction of land use types and build the best method of land use quantification in the long-term planning process. At the same time, the evaluation of regional potential should be further refined, the smaller administrative regions should be evaluated, the specific potential scope should be clarified, and the direction of land use should be more carefully judged. In addition, in the following research, we combine landscape evaluation with ecological evaluation to more comprehensively determine the direction of critical adjustment of land use structure, which is widely used in spatial planning.
5. Conclusions
This study used ArcGIS spatial data analysis methods with land use dynamics, the land-use the comprehensive index, and other methods to analyze the characteristics and problems of the current land use in Changzhi City. Using GeoSOS-FLUS to explore the suitability probability distribution of various land types and combining the construction land intensiveness, cultivated land reserve resource, and rural construction land consolidation potential evaluation results, the direction of land spatial structure adjustment in Changzhi City is proposed. Changzhi cultivated land, forest land and grassland accounted for more than 85%, and their area decreased from 2010 to 2018. Luzhou District has the highest construction land intensity at 0.65. Licheng County (0.64) has the highest development potential for cultivated land reserve resources. Xiangyuan County and Tunliu District have the most significant potential for construction land consolidation, 6998.42 and 5543.13, respectively. In Changzhi, there are problems such as a large reduction of cultivated land in land use, prominent contradictions between man and land, and a low degree of intensive land use. Combined with the suitability probability distribution of each land use type, it is recommended to expand construction land with Luzhou District as the center, and Tunliu District as the center. In the area adjacent to Luzhou District with a large amount of construction land, the coordination of land use should be the focus of planning. The characteristics of this research are mainly reflected in the use of combined methods to explore the land use structure of Changzhi City, providing a new perspective on the optimization of the land use structure of Changzhi’s long-term development, providing a new approach to the planning and design of land and space.