The identification of regional production-living-ecological space (PLES) is the basic work for the optimization of territorial space, which can point to the direction for the protection, utilization and restoration of regional territorial space. Identification and optimization of PLES in an ecological foundation area in the upper reaches of the Yangtze River is of great significance for ensuring national ecological security and promoting sustainable social development. In this study, Jiangjin District, located at the tail of the Three Gorges Reservoir area, was selected as a case study. Moreover, based on the land use data of the study area in 2018, the coordination among production, living and ecological functions are analyzed, and the PLES is identified by using the evaluation method of land production-living-ecological function (PLEF) and the coupling coordination degree model. Then, we formulated an optimized zoning scheme of the PLES according to the principles of ecological priority, area advantage and coordinated development. The results show that (1) The living function and production function presented obvious spatial consistency in the study area, while the spatial distribution of ecological function and production function presented significant spatial complementarity. (2) Four categories of spatial combinations can be identified in the study area. Overall, the study area presented a national spatial pattern with production-living-ecological balanced space (PLEBS) and ecological space (ES) as the main body. (3) The PLES in the study area can be divided into four categories. The ecological function should be determined by the ecological conservation area as the primary responsibility, and the comprehensive improvement zone should further improve the coupling and coordination relationship among the PLEF. Moreover, the main production-living and ecological improvement zone and the main production-ecological and living improvement zone should realize the coordinated development of the PLES on the basis of strengthening the leading function.

The sustained growth of non-farm wages has led to large-scale migration of rural population to cities in China, especially in mountainous areas. It is of great significance to study the spatial and temporal pattern of population migration mentioned above for guiding population spatial optimization and the effective supply of public services in the mountainous areas. Here, we determined the spatiotemporal evolution of population in the Chongqing municipality of China from 2000–2018 by employing multi-period spatial distribution data, including nighttime light (NTL) data from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) and the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS). There was a power function relationship between the two datasets at the pixel scale, with a mean relative error of NTL integration of 8.19%, 4.78% less than achieved by a previous study at the provincial scale. The spatial simulations of population distribution achieved a mean relative error of 26.98%, improved the simulation accuracy for mountainous population by nearly 20% and confirmed the feasibility of this method in Chongqing. During the study period, the spatial distribution of Chongqing’s population has increased in the west and decreased in the east, while also increased in low-altitude areas and decreased in medium-high altitude areas. Population agglomeration was common in all of districts and counties and the population density of central urban areas and its surrounding areas significantly increased, while that of non-urban areas such as northeast Chongqing significantly decreased.

China’s social and economic development is in a critical period of transition. With the implementation of the Rural Revitalization Strategy, new rural industries and new formats have developed rapidly. Profound changes have taken place in the human–land relationship, population structure, industrial structure, and rural functions in the vast rural areas, which have a huge impact on the function and value of rural homesteads. The functional evolution of rural homesteads has a strong driving effect on the change of function value of the homestead. The functional value of rural homesteads is affected by the social and economic development conditions, location, resource endowment, land use policy, rural land trading market, the development of new industries and new formats, and the evolution of homestead function; different homestead functions have different values, especially in the non-agricultural production function and asset function of the homestead. To revitalize the idle and inefficient use of the homestead and fully manifest its value when the homestead is transferred or withdrawn, it is necessary to scientifically calculate the homestead value according to the principle of “what function is lost and what value is compensated”. This paper adopts basic geographic data, rural land transaction data, and social and economic data, and it uses participatory rural appraisal, the land estimation method, and the comparative analysis method. According to the classic theory of “structure determines function and function determines value” in systems engineering, the equivalent substitution method and market value method are used to measure and compare the functional values of traditional agricultural villages and tourist homestay villages before and after the functional evolution. The results show that (1) the leading functional evolution of homestead landlords is closely related to the level of social and economic development. The change in the functional value of the homestead presents the same law as the evolution of its leading function. (2) The functional evolution of the homestead has a strong driving effect on its value change. The increase in value caused by the functional evolution of homesteads in homestay villages is significantly higher than that in traditional agricultural villages. (3) The functional value of the homestead is affected by the social economy, location, resource endowment, land use policy, rural land trading market, business development, and the functional evolution of the homestead. (4) It is suggested that the state formulates the compensation standard for voluntary and paid withdrawal of homesteads according to the “functional value theory of homesteads”, to reduce the unfair value compensation caused by location differences.

Food security remains a primary concern because of the large population and scarce land resources in China, and it is a core task to determine the appropriate proportion and scale of fallowing for fallow systems. The aim of this study was to systematically estimate the grain production potential (GPP) of existing and unexcavated cultivated land due to land use change from 1990 to 2017 and calculate the theoretical fallowing scale by using a population carrying capacity model. The reserved GPP from cultivated land to be excavated was 7470 × 10⁴ t in China, and the GPP stored by the change in grain yield per unit, multiple crop index (MCI) decline, and agricultural structure adjustment were 921 × 10⁴ t, 4321 × 10⁴ t, and 7760 × 10⁴ t, respectively, and the lost GPP caused by construction land expansion was 5287 × 10⁴ t. The population carrying capacity of cultivated land in China was estimated to be 1.469 to 1.515 billion in 2017 on the basis of the national average living standard. The proportion of the population that could be fed more was between 6.28% and 9.54% depending on the number of people included, which provided an opportunity to implement the fallowing system in China. Meanwhile the proportions of the theoretical fallow scale were 6.28% and 9.54%, and the fallow scale ranged from 850 × 10⁴ hm² to 1296 × 10⁴ hm² under the premise of fully tapping the potential of cultivated land. In addition, taking the decline in MCI as an example, the grain yield reduction was equivalent to the grain yield of 829 × 10⁴ hm² of newly reclaimed cultivated land over the past 30 years, which saved 621.48 billion yuan. The costs and benefits when formulating relevant policies of land utilization should be considered, and exploiting the productive capacity of cultivated land that exists is better than reclaiming new cultivated land.

With the development of China’s national economy from the middle- and low-income stages to the middle- and high-income stages, the function of homesteads has undergone a significant evolution. Clarifying the evolution laws, characteristics, and dynamic mechanisms of various functions of homesteads can provide a basis for revitalizing the use of idle homesteads and promoting rural economic development. It can also provide theoretical guidance for implementing the Rural Revitalization Strategy. This paper uses statistical data and household survey data to establish a theoretical analytical framework for the functional evolution of rural homesteads under the background of changes in national economic-income levels. This study adopts comprehensive index model evaluation methods, participatory rural assessments, and participatory rural-mapping methods. This study reveals the characteristics and driving mechanism of the functional evolution of homesteads at different stages of economic development in China and verifies it from a microscale through typical rural homestay villages. The results show that the functional evolution of rural homesteads in China has apparent stages. In the middle- and low-income stages, the basic functions of the rural homestead are the living function, agricultural-production function, and social-security function. In the middle- and high-income stages, the living function, the nonagricultural-production function, and the asset function are the main functions. The functional evolution of rural homesteads is driven by both macro and micro factors. The multifunctional use of rural homesteads can fully activate the use rights of homesteads, realize the appreciation of the functional value of rural homestead assets, and provide primary power for rural social and economic development. Furthermore, it can play an essential role in China crossing the “middle-income trap”. The research results provide evidence for understanding the functional evolution law of rural homesteads and contribute to the rural geography of multifunctionality.