As China's urbanization has entered the middle and later stage and the improvement of well-being of residents has become a core goal, the transformation from "top-down" system goals optimization on the supply side to "bottom-up" multi-dimensional goals coordination on the demand side has become a new perspective to understand the connotation of urbanization. Based on the perspective of the human living conditions, the humanities environment, and human-city relationship, this paper constructs a connotation framework and index system of urbanization. Furthermore, Theil index is employed to analyze the spatio-temporal differentiation characteristics of China's urbanization before and after the implementation of the new-type urbanization strategy. Finally, in terms of both direct and indirect effect mechanisms, the mechanism framework of urbanization differentiation is constructed, and its evolution pattern is revealed by using Variance Decomposition and Geodetector. The results show that: since the implementation of the new-type urbanization strategy in 2014, China's urbanization has made remarkable achievements, with a steady improvement in human living conditions and human-city relationship, and there is still much room for improvement in the humanities environment. The high-level areas of urbanization are mainly distributed in coastal areas, and expanding to inland areas along the Yangtze River Basin and Yellow River Basin. The regional differences of urbanization gradually decrease, but the contribution rate of inner-regional differences shows an expanding trend. Differences in human living conditions and human-city relationship are the main factors of urbanization differentiation, but the contribution of differences in humanities environment is gradually expanding after 2014. Opening up and scientific & technological innovation are the main influencing factors of the difference in human living conditions. With the implementation of the new-type urbanization strategy, the impact on differences in humanities environment of the government finance gradually diminishes. Resource endowments have a relatively strong influence on differences in human-city relationship. This study can provide theoretical and empirical support for promoting the development of urbanization in China.

GIScience inherits the spatial analysis tradition of geography. Given that "spatial is special", GIScience needs to highlight spatial effects when constructing methods for geographical analysis. The research presents an explicit definition of spatial effect. By formalizing core GIScience concepts including space, location, field, distance, and region, we identify four types of spatial effects, namely spatial heterogeneity effect, neighbor effect in spatial dependence, distance decay effect in spatial interactions, and scale effect in spatial zoning. A unified framework is constructed to cover the four spatial effects based on the inherent linkages among them. We argue that spatial heterogeneity effect is the most fundamental one. While spatial dependence and spatial interaction are two basic geographical processes that represent the second-order relationships between two locations, neighbor effect and distance decay effect reflect the impacts of space. Scale effect is raised when aggregating attributes using regional units. Hence, the four types of effects form a hierarchical system. From a methodological perspective, this paper summaries related GIScience tools that implement different effects, and emphasizes the value of geospatial artificial intelligence for revealing and quantifying spatial effects.

With urbanization and industrialization, cultivated land in hilly regions of China has been gradually marginalized. Abandoned cultivated lands have ranged from inferior sloping land and extended to high-quality terraces. The abandonment of terraces will lead to a series of social and ecological problems, especially with large-scale abandonment. Therefore, the degree and spatial distribution of terrace abandonment should be evaluated scientifically to address the issue of abandonment as well as its effects. This study investigated the extent of terrace abandonment in China via a questionnaire sampling method. Based on 560 village questionnaires from 329 counties in China, the scale of terrace abandonment was calculated and the spatial heterogeneity characteristics and primary reasons for terrace abandonment were further analyzed. Study results showed that: (1) The phenomenon of terrace abandonment was observed throughout China, occurring in 54% of all the villages investigated; 9.79% of the total terraced areas have been abandoned. (2) The degree of terrace abandonment showed a spatial pattern of "high in the south and low in the north". The degree of terrace abandonment was higher in the southern hilly mountains, and the middle and lower reaches of the Yangtze River was the most serious. (3) The primary factors related to terrace abandonment were found to be labor migration, the degree to which terraces have been mechanized, irrigation conditions, and farming traffic conditions. Measures that include improving the degree of terrace mechanization should be enacted to address the problem of terrace abandonment. An orderly "conversion of cropland" could be applied to poor-quality terraces. Changing the planting structure, strengthening new agricultural infrastructure, and encouraging circulation and large-scale operations are options that could be applied to good-quality terraces.

The modern international and domestic science advancements have brought forward new opportunities as well as higher requirements to the development of geographic science in China. In planning the disciplinary structure of geographic science in the "Development Strategy of Discipline and Frontier Research in China (2021-2035)", we propose a modified disciplinary structure for the geographic science in the new era. The geographic science in China can be categorized into four secondary disciplines, i.e., integrated geography, physical geography, human geography, and information geography, considering the current situation and development outlook of geographic science. The tertiary disciplines under each secondary discipline are nearly fully developed, and a few quaternary disciplines under tertiary disciplines have already been widely accepted and used. We hope this new disciplinary structure can play a breakthrough role for improving the branches of geographic science, promoting the development of emerging disciplines under the framework of geographic science, and better serving the international and domestic development needs in the new era.

We propose a theoretical framework for assessing the ecological benefits provided by national key ecological projects in China over the past 20 years. A dataset consisting of six primary indicators and nine secondary indicators of ecosystem structure, ecosystem quality, and ecosystem services for the period 2000-2019 was generated using ground survey and remote sensing data. Ecological benefits were quantitatively evaluated following the implementation of national key ecological projects in China. Areas with medium, relatively high, and high degrees of ecological restoration accounted for 24.1%, 11.9%, and 1.7% of the national land area, respectively. Degrees of ecological restoration were higher in areas with a greater number of ecological projects. Areas with relatively high and high degrees of ecological restoration were mainly concentrated in the Loess Plateau, the farming-pastoral zone of northern China, the Northeast China Plain, and an area spanning the border areas of Sichuan, Yunnan, Guizhou, Chongqing, and Hunan. The relative contributions of climatic factors and ecological projects to changes in vegetation net primary productivity were 85.4% and 14.6%, respectively, and the relative contributions of climatic factors and ecological projects to changes in water erosion modulus were 69.5% and 30.5%, respectively. The restoration potential of national vegetation coverage was 20%, and the restoration potential percentages of forest and grassland vegetation coverage were 6.4% and 23%, respectively. Climatic conditions can inhibit ecological restoration. Areas with relatively high and high degrees of ecological restoration were mainly distributed in areas with an annual average temperature greater than 0 ℃ and annual precipitation greater than 300 mm. Therefore, the limitations associated with climate conditions should be considered during the implementation of national ecological projects. The implementation of single ecological projects or single ecological restoration measures should be avoided, the use of combined measures should be emphasized, and the benefits of ecological investment funds should be maximized.

Despite the initial development goals achieved, China's macro-economy is still deeply affected by the external environment and stuck in its own structure at the same time. In retrospect, not until 1949 with the founding of the People's Republic of China did China's budding regional economy witness the prominence of a fixed development pattern shifting from a spontaneous to an actuating one. After comparing the three regional economic practices, this paper finds that each development stage has its corresponding development strategy. At the same time, several development patterns, namely, the coastal and inland areas, the three regions, and four plates were formed accordingly. Furthermore, through combing the literature and historical facts, this paper determines the historical starting point, division criteria and division scheme of China's regional economic development before summarizing three main lines and also contradictions therein: the government-market relations against the background of market reform, the coastal-inland relations against the tide of economic zonation, and the urban-rural relations against the trend of urbanization. Based on the above, the paper constructs a three-dimensional model out of the spatio-termporal process of China's regional development before proposing new historical stages from the perspective of economic system modernization. These historical stages are: industrial economy, special zone economy, district economy, regional economy and urban network economy. Finally, from the urbanization angle, this paper concludes that for different urbanization stages, regional policies should be industrial policies, factor policies, fiscal and tax policies sequentially.

The orderly development of county urbanization, as an effective driving force for the integrated development of urban and rural areas in the new era, promotes the interaction and flow of elements between urban and rural territorial system, the optimization and adjustment of industrial structures, the optimal allocation of resources and markets, and the organic integration of urban and rural territorial system. The results show that: (1) From 2000 to 2020, the county urbanization in China developed rapidly, and the regional differences in spatial and temporal dynamics were significant. The county urbanization rate in the eastern coastal, central suburbs and northern border areas was high, while it is low in southwest China, rural areas of the central region and most parts of Tibet and Xinjiang. In 2020, to the east of the Hu Huanyong Line, the northeastern region, northern Hebei, Shanxi-Shaanxi-Henan region, eastern Sichuan, and Yunnan-Guizhou region became high-value areas for urbanization rates at the county level. There are 716 counties with urbanization rates exceeding 50%, including the Pearl River Delta, the Yangtze River Delta, the Beijing-Tianjin-Hebei region, the Chengdu-Chongqing region, the middle and lower reaches of the Yangtze River, the border areas of Inner Mongolia, and the southeastern coastal areas of Jiangsu, Zhejiang and Fujian, accounting for 38.3% of the country's total. (2) The county urbanization in China is the result of the combined effects of factors such as population, economy, society, and culture. The level of economic development, natural environment conditions, infrastructure construction, geographic locations, public resource supply, professional entrepreneurial clusters, and macro policies affect the direction, scope and depth of county urbanization. It is predicted that by 2035, the urbanization rate of China will reach about 76.04%, and that of counties will be about 64.38%. In the future, we should strengthen the adjustment and optimization of county population, economy, society and spatial organizational structure. (3) There are five types of county urbanization in China, including factor agglomeration urbanization in counties around big cities, industrial agglomeration-driven urbanization in counties with specialized function, agricultural modernization-led urbanization in counties with main agricultural production areas, ecological conservation urbanization in counties with ecological function areas, and concentrated urbanization in counties with population loss. (4) County urbanization takes county and key towns as important spatial carriers for the agglomeration of urbanization elements, and forms a multi-level system of residence-industry and industry-city coordination. The rational spatial distribution of factors such as the development of industrial integration and population resources will further promote the interactive flow of urban and rural elements, the integration of urban and rural industries, the equalization of urban and rural residents, and the equalization of urban and rural infrastructure, and enhance urban-rural integration and network development.

Mountain altitudinal belts are the miniature of horizontal differentiation and succession of climatic and vegetational zonation. However, altitudinal belts' vertical range, transition model, inner structure and combining pattern vary from place to place. In Mt. Taibai of the central section of China's north-south transitional zone, we have found an altitudinal belt with the largest range in the world, namely, the montane deciduous broad-leaved forest, which extends continuously from the mountain base to about 2800 m, including basal oak belt, typical oak belt of two sub-belts and cold-tolerant pioneer birch belt of two sub-belts, which could otherwise develop independently. Characterized by a "three layers and five sub-belts" structure, this "super altitudinal belt" is much vertically broader than the threshold of 1000 m for normal altitudinal belts. Its formation is closely related with its transitional geographic location, integral spectrum of altitudinal belts in central Qinling Mountains, rich and diverse species of deciduous woody plants, and their strong competitiveness. The finding of the super altitudinal belt has multiple significance: Its existence is another significant physio-geographic feature of China's north-south transitional zone; it shows that an altitudinal belt may have rather complex inner structure and broad vertical range in some special mountain environment. This broadens our understanding of altitudinal belt structures and their mechanisms, and is of great significance for developing structural theory for montane altitudinal belts. This finding also demonstrates that there are many big questions for us to explore and study in the north-south transitional zone, and it is expected that our finding could trigger in-depth study of local climate and biodiversity responsible for the formation of this super belt, and of the complex structure and ecological effect of China's north-south transitional zone.

Deconstructing rural spatial characteristics is the precondition for building rural spatial governance system in the new era, and multi-scale rural spatial characteristics and its governance path would effectively support the modernization of the national governance system. Based on the comprehensive, regional and mobile thinking paradigm of geography, this paper deconstructs the multi-scale rural spatial characteristics, identifies its internal operating logics, summarizes its governance dilemmas, constructs a multi-scale rural spatial governance framework that is based on geographical analysis paradigm, explores feasible governance paths, and constructs a multi-scale rural spatial governance system research plan, namely, "characteristics identification-dilemma analysis-governance framework-governance path". The paper finds that: (1) to analyze the operating logics of the multi-scale rural space through the comprehensive, regional and mobile analytical thinking of geography, it is necessary to understand the mechanism of action of scale synthesis, scale differentiation and scale flow to the multi-scale rural spatial characteristics, highlighting the comprehensive characteristics of rural space, strengthening rural spatial heterogeneity, and integrating rural spatial mobility. (2) The lacking urban-rural spatial overall planning, unsmooth spatial mobile network and not-reflected different types of rural spatial value are the key dilemmas in the rural spatial governance, which need to be addressed. (3) The multi-scale rural spatial governance framework of "comprehensive spatial governance-spatial zoning governance-spatial mobile governance" could effectively solve the problems of urban-rural spatial integration, regional spatial coordination and spatial network blockage. (4) Integrating urban-rural comprehensive governance, innovating regulation control to improve regional governance and balancing the configuration of spatial development right to achieve mobile spatial governance are feasible paths for multi-scale rural space governance. In conclusion, clarifying the multi-scale rural spatial characteristics in the new era and constructing a scientific governance system could provide theoretical support to promote integrated urban-rural development and rural vitalization strategy.

Using data of the latest three decennial censuses, this paper systematically analyzes the overall spatial pattern, changing trends, and influence mechanisms of China's population distribution since 2000. The study reveals that the general population distribution pattern of "dense east and sparse west" in China has not changed, which is determined by the differences in natural geographic environments on the two sides of Hu Line. In the first decade of the century, population concentration was mainly found in the southeastern area, but it has been observed in all regions in the recent decade. Provincial capitals have become the winners of population competition and the advantages of population growth of provincial capitals have been further strengthened in the recent decade compared with 2000-2010. However, the administrative power-led effects of the increasing dominance of provincial capitals will gradually weaken with the development of their provinces. The regional differentiation of population changes is also apparent: coastal region gradually forms a dense belt of population and towns with solid population attraction based on the development of urban agglomerations; the northeast region almost turns to a complete population shrinking status; central provinces still compete fiercely for population based on their capitals; the population of Sichuan, Chongqing, and Guizhou has stopped the decline and returned to growth; and the northwest region faces the risk of population loss. In addition, this paper finds that the driving factors of regional population growth have gradually changed from economic factors to both economic and amenity factors, and the difference of amenities among regions may become an important factor for future changes in China's population geography.

According to the Ministry of Water Resources of the People's Republic of China, the number of casualties in flash flood disasters accounts for nearly 70% of flood disaster casualties in recent years and flash flood has become one of the major natural disasters causing casualties in China. Flash flood regionalization is fundamental for implementing the local measures of the flash flood prevention and mitigation according to local conditions. Using results from existing flash flood relevant physiographical regionalization schemes, and in accordance with the principles of comprehensive, dominant factors, the relative consistency within units, the relative difference between units, the integrity of spatial distribution and the hierarchical divisions, this paper firstly constructs an index system of the flash flood trigger factors and its underlying surface environment for the flash flood regionalization in China. In the combination of top-down and bottom-up regionalization, the hybrid self-organizing-map-based spatial clustering algorithm is then built. Finally, nine homogeneous regions at the first-grade and thirty-three subregions at the second-grade are delineated for flash floods in China. The historical flash flood events and the Geodetector method are adopted to evaluate the developed regionalization schemes. Results show that the first-grade and the second-grade flash flood regionalization schemes in China can respectively provide the determinant power of 66.4% and 75.4% for the spatial distribution of historical flash flood events in the whole country, indicating the developed flash flood regionalization has a good spatial consistency with the distribution of historical flash flood events with different densities. The developed flash flood regionalization not only effectively delineates the regional differentiation pattern of flash floods, but also provides a scientific basis for the implementation of localized flash flood prevention and mitigation measures in China, which benefits for the sound development of flash flood disasters prevention and management in China.

The land conversion processes concerning non-agricultural and non-grain production areas have prominently decreased arable land availability, which substantially impacted grain production capacity and threatened national food security. Thus, it is critical to establish a novel scientific approach to identify spatio-temporal evolution patterns of land conversion and its influencing factors in different stages. This study evaluates the evolutionary characteristics of non-agricultural and non-grain fields by constructing a comprehensive index system that considers factors like cultivated land resources, social and economic conditions, and farmers' subjective perspectives, using a county as the basic research unit. For a comprehensive analysis, a geographical detector model was utilized to quantify driving factors in different stages. The results indicated spatial clustering effects for non-agricultural and non-grain fields throughout China, particularly in the eastern region beyond the "Hu Huanyong Line". Further analysis revealed a spatial pattern for non-grain conversion phenomenon was more intense in the southwestern than the northeastern fields. Over the past four decades, non-agricultural fields recorded an area expansion, but the year-wise area increase was gradually reduced, while non-grain areas exhibited a "growth-stable" change pattern. Although progress in non-grain was less in primary producing areas over the last 40 years, an increase of 1.49 times and 1.33 times was recorded from 2010 to 2020 in PSB (production and sales balance area) and Mrt (marketing) areas, respectively. Compared to the period 1980-2000, the rate of non-agricultural conversion in primary producing areas decreased by 77% during 2010-2020, while the rate of non-agricultural conversion increased by 1.63 and 4.65 times for PSB and Mrt regions, respectively. Based on these findings, this paper puts forward suggestions, such as setting control rules and subsidy mechanisms according to area classification, promoting control policies based on regional considerations, strengthening dynamic monitoring and risk warning, as well as enhancing supervision and assessment.

Data center is a new infrastructure system based on new development concepts, technological innovation, and information networks. It provides services for digital transformation, smart upgrading, and integrated innovation to meet the needs of high-quality development. The new infrastructure covers the construction of 5G base stations, intercity high-speed rail, intercity rail transit, new energy vehicle charging piles, big data centers, artificial intelligence, and industrial internet. It could promote resource integration, nurture new growth points, and shape new locations. Analyzing the spatial patterns of new infrastructures and their influencing factors is of great significance for understanding the regional development advantages. Using the data center as an example, this paper explores the spatial distribution and determinants of new infrastructure. Since the data center is not only infrastructure but also a strategic emerging industry, it is different from traditional infrastructure in terms of technical requirements and energy consumption. Since this difference will be reflected in the spatial layout, this paper proposes the macro layout principle of the data center. Then, the evolution characteristics and influencing factors of the spatial pattern of data centers in China are analyzed, and the following conclusions are drawn: (1) The macroscopic distribution of data centers should follow four principles: demand-oriented, cost oriented, operating environment-oriented, and safety oriented. (2) The distribution of data centers presents a spatial structure centered on the Beijing-Tianjin-Hebei region, Yangtze River Delta, Pearl River Delta, and Chengdu-Chongqing urban agglomeration. (3) Economic development, internet development, the number of high-tech enterprises, labor costs, and educational institutions have a positive impact on the macro layout of data centers. The impacts of location conditions, land costs, and layout policies of data centers on their macro layout begin to appear at a certain stage. (4) There are three types of data center distribution models in China: demand-orientated, cost-oriented, and demand-cost-operating environment-oriented. At present, the data center in China is demand-oriented and will develop into a comprehensive demand-cost-operating environment-oriented model in the future. Our conclusion could provide guidance and suggestions for scientific site selection and the optimal layout of data centers.

Human geography is a discipline which studies the formation and evolution of the geographical distribution pattern of human activities. The main research objects of human geography focus on human activities and human-earth relationship. The scientific questions to be answered by human geography cover both natural science and social science, and thus it has distinctive interdisciplinary features. In China, the economic and social processes of human activities are playing an important role in explaining the law in human geography discipline as human society development is approaching or has entered the post-industrialization stage. The logics and methods of social science have become important tools through which the changes in processes and patterns of human geography can be reasonably discussed and properly understood. Research methodology of human geography shows integration characteristics between natural sciences and social sciences. The outcomes of human geography research reveal scientific laws in geographical distribution pattern and evolution of human activities. It becomes one of primary disciplines for both the national and local governments to manage and optimize the pattern of spatial development and protection. It has wide applications in spatial planning, regional strategy and policy making, and the modernization of spatial governance. The unique feature in integrating academic research and policy-making applications provides human geography discipline in China a superiority of leading the world in the discipline. Besides comprehensive human geography, human geography in China has five subdisciplines, namely, economic geography, urban geography, rural geography, social and cultural geography and political geography. Each subdiscipline has priority and key research fields, and coordinates with the rest of subdisciplines.

Urban-rural integrated development is an advanced stage in the evolution of the urban-rural relationship, and it is also the basic path and main goal for the implementation of rural revitalization. Scientifically understanding and identifying the integration stage and its current level of urban-rural development in China is the prerequisite basis for promoting urban-rural integrated development and rural revitalization. Based on the concept connotation, this paper constructed a multi-dimensional evaluation system of urban-rural integrated development at the prefecture level. The process status and spatiotemporal divergent characteristics of urban-rural integrated development in 336 prefecture-level regions in China from 2000-2018 were portrayed and revealed. The results show that: (1) The current state of urban-rural integrated development in China is generally at a low-to-middle level, showing a heterogeneous spatiotemporal pattern with apparent gradient divergence. The integrated development level of the Pearl River Delta, Jiangsu and Zhejiang provinces, and the Shandong Peninsula is high, but the regions distributed to the west of the "Hu Line" develops slowly. (2) According to the level and characteristics of integrated development, the 366 prefecture-level regions can be divided into four types: integrated development, tending integration, imbalanced development, and lagging development, with a more active transformation between the latter three types. (3) The development level of urban-rural economic integration is higher than that of demographic and social integration, while the development process of urban-rural spatial and ecological integration shows some natural zonal divergent characteristics. Finally, we identified the problem areas for different types of integrated development and explored the regional promotion path of urban-rural integrated development, which could provide scientific references for the strategies of regional urban-rural development and rural revitalization.

China is a large agricultural country, and issues concerning agriculture, rural areas and farmers are closely related to national economic and social development. To achieve the "Two Centenary Goals", rural revitalization strategy has become the choice to resolve unbalanced urban-rural development and inadequate rural development in China. Rural development is a comprehensive process of cycle accumulation and dynamic evolution of rural regional system. Thus, it is of great significance to systematically analyze the process and regional pattern of rural development to scientifically promote the implementation of rural revitalization strategy in the new era. Based on the theory of human-earth areal system and human-earth system science, this study examines the process and features of rural development in China from 1978 to 2050, discusses the internal relationship between rural transformation and rural revitalization, reveals the spatial pattern of the level of county rural revitalization in 2017, and finally puts forward the key problems and countermeasures for rural revitalization in the new era. Results show that the evolution of China's rural development in the period of 1978-2050 can be divided into three stages, i.e. solving the problem of food and clothing (1978-2005), building a well-off society (2005-2020) and realizing prosperity (2020-2050). In general, it is a dynamic and continuous process from low-level and basic-type to high-quality and innovation-type. Rural revitalization is a special stage of rural transformation, and a strategic choice to solve the prominent problem in rural development when it has evolved to a certain stage, thus boosting rural development to a higher stage. In 2017, when rural revitalization strategy was initiated, the level of rural revitalization in 57.3% of the counties in China was between 0.40 and 0.50, and there was an obvious gradient differentiation from the east to the west, with significant clustering characteristics and positive correlation. Specifically, the counties featured by "high-high (H-H)" clustering were mainly distributed in the third step of the terrain and the middle of Sichuan Basin; while the counties featured by "low-low (L-L)" clustering were concentrated in western China except Sichuan Basin, the eastern part of Inner Mongolia and the north of Tianshan Mountains. Due to the regionalism, stage and the difference in constraints of rural development, the focuses of rural revitalization in the new era lie in scientifically identifying the targeting areas of rural revitalization, comprehensively judging the trends of rural development, and systematically diagnosing the dominant constraints of different types of rural areas, so as to take targeted measures to make up for the shortcomings of the modernization of agriculture and rural areas. Besides, it is necessary to fully understand the interactions between urban and rural areas, thus promoting urban-rural integrated development.

Understanding the influencing factors and controls of rainstorm-induced floods, which have caused tremendous losses of human lives and national economy, is a pressing need for flood risk management in China. Based on the meteorological disaster census data of counties in China, hourly precipitation data at 2420 stations, statistical yearbook, terrain data and other data, the authors (1) investigated the spatiotemporal pattern of flood impacts in China over the period from 1984 to 2007 using trend analysis techniques and (2) explored the driving factors of the spatiotemporal pattern by adopting the geospatial statistical analysis tool (Geodetector). This study considered the spatiotemporal patterns and their interplays among county-level flood impacts (i.e., flood-induced mortality rate, proportion of population affected, and economic loss in percentage), disaster-formative environmental factors (i.e., population density, urban population percentages, average elevation, river density, average slope, and average distance to the seashore), and extreme precipitation characteristics (i.e., annual average volume and duration of extreme rainfall). The results show that: (1) there were no consistent temporal trends of extreme rainfall characteristics over the study period across China. (2) The frequencies of flood disasters in the Yangtze and Pearl rivers and southeast coastal areas increased significantly, but the casualties over these regions decreased. (3) Flood-induced casualties, proportion of population affected and economic loss in percentage increased in Northwest China; and meteorological factors, disaster-formative environment factors such as geographical conditions and social economy, and geographical conditions contribute mostly to the proportion of population affected, flood-induced death and economic loss in percentage. These results indicate that more attention should be paid to improving the flood control capacity of small or medium-sized cities in the inland river basins, especially in Northwest China, and we should recognize the important roles that disaster-formative environment plays in triggering flood losses.

At present, the empirical analysis of regional dual-nuclei structures at the national level is still relatively rare. How to define the provinces with the characteristics of dual-nuclei structures and analyze their impact needs further empirical discussion. In this paper, the spatial Dubin model and the data of 259 prefecture-level cities are used to analyze the distribution characteristics of regional dual-nuclei structure in China and its influence on provincial development. The empirical results show that 11 provincial-level regions (hereafter provinces) in China show the characteristics of dual-nuclei structure. The regional dual-nuclei structure plays a significant role in promoting the economic development of the province, but the northern and southern regions show great differences. The regional dual-nuclei structure has a promoting effect on provincial industrial agglomeration and helps to promote the improvement of local scientific and technological innovation. In general, compared with some single-core provinces with small scale and weak radiation driving force in some provincial capitals, the regional dual-nuclei structure can make up for these shortcomings to a certain extent by virtue of the number of central cities and spatial distribution, which is more conducive to driving local economic development and scientific and technological innovation.

Terrestrial recycling of green water, which is created through a continuous cycle of evapotranspiration, atmospheric transport, and terrestrial precipitation, serves as bridges connecting hydrosphere, atmosphere, biosphere, and anthroposphere. Limited knowledge of terrestrial recycling may underestimate the impact of human activities on water and ecology. This study focuses on the structure of China's green water recycling (CGWR) and quantifies the contributions of natural and human ecosystems. Results indicate a high green water recycling ratio (50.4%) and a large recycled amount (2.75 trillion m³/a) over China, with significant south-to-north transport structures over eastern China, southwest-to-northeast transport structures from southwestern China to northern China, and high self-recycling structures in western China. The grassland-dominated Qinghai-Tibet Plateau provides the largest amount of green water (about 800 billion m³/a) and serves as the most critical region for CGWR. The forest-dominated southern hilly region and Yunnan-Guizhou-Sichuan region play a crucial role in supplying green water to a wide area of China. The cropland-dominated Middle-Lower Yangtze Plain and the grassland-dominated Loess Plateau are the key hubs for south-to-north and southwest-to-northeast transport of green water. The structure of CGWR is driven by large-scale geosystems such as ecosystems and atmospheric circulation systems, and has strategic implications in the following three aspects. First, CGWR serves as the "domestic cycle" of water, based on which a general domestic-level water governance framework can be established. Second, CGWR is a representative picture of the water-related processes in the Mountain-River-Forest-Farmland-Lake-Grassland-Desert (MRFFLGD) system and serves as a critical pivot to actualize the conservation and improvement of the MRFFLGD system. Finally, CGWR, together with inter-basin water resources transfer and virtual water transfer, forms a complete picture of China's inter-basin water transfer. The scientific coordination and integration of the three processes present a new approach for achieving spatial equilibrium between China's water resources and economic development.

Under the background of promoting more balanced and fuller regional development in the new era, standing at the strategic height of national regional coordinated and balanced development, it is necessary to comprehensively consider the natural environment, the unbalanced situation of economic and social development and the reality of widening gap on both sides of the Hu Huanyong Line, and put forward the basic idea of the Hu Huanyong Line to achieve micro-breakthrough along the Bole-Taipei Line. The Hu Huanyong Line is an important dividing line of population geography, natural geography and ecological environment in China, the dividing line of national main function area and national ecological function area, the dividing line of new urbanization main area and non-main area in China, and the dividing line of unbalanced and inadequate economic and social development in China. In the past 40 years, the gap of economic and social development between the two sides of the Hu Huanyong Line has been widening at an accelerating speed. In the next 30 years, the gap can be narrowed to achieve micro-breakthroughs, focusing on achieving "ten 10%", namely, the proportion of population in the northwest half of China will be 10%, the proportion of total economy will be 10%, with the economic growth rate being more than 10%, the proportion of fixed asset investment in the whole society will be more than 10%, the proportion of local fiscal revenue will be more than 10%, the proportion of actual use of foreign capital will be 10%, the growth rate of per capita GDP will be more than 10%, the rate of increase in the absolute difference in the per capita disposable income of urban residents will be controlled within 10%, the rate of increase in the absolute difference in the per capita disposable income of rural residents will be controlled within 10%, and the absolute gap in education resources will be narrowing at an average annual rate of 10%. In order to achieve the strategic goal of micro-breakthrough, this paper puts forward the main paths and countermeasures to narrow the development gap between the east and the west of the Hu Huanyong Line and attain the micro-breakthrough from the aspects of population micro-layout, economic micro-layout, urbanization micro-layout, industrial micro-layout, moderate water diversion nearby, improvement of ecological compensation and transfer mechanism, construction of the Bole-Taipei Line and implementation of the strategy of further development in the western region.

Sustainable rural development is critical to the achievement of global sustainable development goals. Globalization and urbanization, as the key processes, continuously drive the human-earth system to make adaptive responses, promoting the transformation of urban-rural relations. The rural-urban relationship is essentially a mother-child relationship, which is a comprehensive characterization of the transfer of rural humanistic factors, the transformation of man-land relationship and the transformation of urban-rural development in the process of urbanization. However, the traditional cognition of urban-rural relationship ignores the multi-dimensional connections between the rural and the urban as well as the existence of the rural-urban integration system, resulting in prominent drawbacks of rural regions, negatively affecting the urban-rural development rights, and resulting in urban and rural territorial dysfunction and other problems. The key to solve the problems of socio-economic development in China is to reform the urban-biased development strategy, and to innovate the new cognition of rural-urban relationship based on the thinking of "rural maternal effect", which highlights that rural areas nourish the city. Based on the remote coupling and systematic synthesis of the rural human-earth system, modern human geography urgently needs to strengthen the cross-research with physical geography and information geography, create a coordinated observation system of human-earth system supported by the sky-space-ground integration, reshape the global rural development perspective, rural-urban system perspective, and reorganize the global rural human-earth relationship, the rural-urban integration relationship, and the living and employment relationship. Rural human-earth relationship territorial system is the core of rural geography research. The rural human-earth system research should focus on the coupling of rural natural ecosystem and the socio-economic system and their complex interactive processes and effects. Supported by the intersection of multiple disciplines, the expansion of new fields and the cultivation of new disciplines, it should create the collaborative observation technology of human-earth system and methodology of multi-source data fusion computing, the research idea based on process-mechanism-pattern and the technical path of monitoring-simulation-decision support, and explore the organic connection path between rural human-earth system coupling and rural-urban integrated development, regional sustainable development and global common governance.

Food security, one of key components of national security, is a top priority for human survival and social development. In this study, we first sought to determine the influencing factors of crop yields and the process of drought impacts on crop yields. We then systematically reviewed the effects of droughts on major global crop yields from four aspects: field control experiments, statistical models, crop growth models, and remote sensing inversion models. Recent progress in crop yield impact assessment reveals that the current research has changed from single-hazard to multi-hazard, from single target to multiple targets, and from statistical models to a comprehensive model. A bibliometric analysis shows that the volume of research on drought impacts on crop yields has increased exponentially, and the related research theme has undergone a transformation from traditional research on crop water stress to comprehensive research on crop drought impacts and adaptation, reflecting the continuous deepening and integration of research perspectives. Agriculture, plant sciences, and environmental sciences are the three main disciplines in research on drought impacts on crop yields. We need to strengthen the application of geographical thinking, that is, systematic thinking concerning multiple factors and multiple scales to study the coupling of crop yields and water resources in the future. Finally, we suggest the following four priority areas for future research in consideration of the problems and challenges of the existing research: establishing a multi-source database of drought impact on crop yield, revealing the key process and mechanism of drought impacts on crop yields, developing a coupled macro and micro process crop growth model, and establishing a comprehensive monitoring platform system for crop yields and food security. This will help ensure sustainable agricultural development and global food security by improving monitoring, early warning, and scientific management of the impacts of droughts on crop yields.

As the third pole of earth, the Qinghai-Tibet Plateau is an important ecological security barrier in China and an ecologically sensitive area of global climate change. The increasing climate change has posed a major challenge to its ecosystem function and stability. This paper first analyzes the spatiotemporal variation characteristics of the ecosystem pattern of the Qinghai-Tibet Plateau and its key functions including water conservation, soil conservation, windbreak and sand fixation from 2000 to 2020, clarifies the regional differences in ecosystem functions and their importance, and further evaluates the stability of ecosystem functions. And there is no doubt that the stable state will lay a scientific foundation for the plateau to build an ecologically civilized highland and launch protection and restoration projects. The results show that: (1) From 2000 to 2020, the wetland area of the study area increased and the grassland area decreased significantly. The water conservation and windbreak and sand fixation capacity were improved, and the annual change rates were 3.57 m³/(hm²·a) and 0.23 t/(hm²·a), respectively. However, the overall soil conservation showed a downward trend with an annual change rate of -0.16 t/(hm²·a). (2) The core areas of water conservation, soil conservation and windbreak and sand fixation accounted for 12.7%, 13.9% and 14.2%, respectively. The core water conservation barrier areas were mainly located in southeast Tibet, Sanjiangyuan and Ruoergai. The core windbreak and sand fixation areas were concentrated in the central and western parts of the plateau, and the core soil conservation areas surrounded the plateau. (3) From 2000 to 2020, the water conservation, soil conservation, and wind protection and sand-fixation functions have shown relatively high stability in the southeastern and central parts of the plateau, while relatively weak stability in the western part of the plateau. Combining stability assessment and ecological protection and restoration practices, we can divide the Qinghai-Tibet Plateau into three major categories of 16 ecosystem function zones and carry out differentiated ecological protection and restoration for different core ecosystem functions and zones.

The continuous remote sensing monitoring of land use/cover change at the national scale is of great scientific significance for land spatial planning and blueprint drawing of "Beautiful China" in the new era. Landsat 8 OLI, GF-2 and other satellite remote sensing data were used to develop the data of land use change across China during 2015-2020 and China Land Use/Cover Dataset in 2020 (CLUD 2020) by integrating remote sensing big data and expert knowledge-assisted human-computer interaction interpretation methods. Long time series land use dynamic database at a 30-m resolution in China was established at 5-year interval in the end of 1980s-2020. On this basis, the general trend, regional differences and main characteristics of land use change in 2015-2020 were revealed from national and regional scales. The research indicated that integrating vegetation cover change at a 30-m resolution and land change information generated by remotely sensed big-data cloud calculation into the expert human-computer interaction interpretation can effectively improve the efficiency of mapping and the accuracy of land use change detection. The overall accuracy of CLUD 2020 first-level type mapping reaches 95%. In general, the intensity of territorial development entered a stable state compared with 2010-2015. During the period, the cropland continued to decrease. Nationwide farmland was encroached by urban development and construction, paddy fields in Northeast China continued to decrease, and cultivated land in Xinjiang was reclaimed in the south and abandoned in the north. The built-up land continued to increase, showing a spatial pattern that "the expansion of built-up land changed from the agglomeration of coastal areas and mega and large cities in 2010-2015 to the surrounding sprawl of large, medium and small towns in the central and western regions in 2015-2020". Although the area of natural ecological land for forest and grass continued to decrease nationwide, the intensity decreased compared with 2010-2015. Under the continuous impact of climate change, the area of water in the Qinghai-Tibet Plateau increased significantly. The pattern of land use change is closely related to the national macro strategy for high-quality development during the "13^th Five-Year Plan" period (2016-2020) and ecological civilization construction, as well as the impact of climate change.

Internal migration in China has presented a series of new characteristics recently. The secondary migration and spatial redistribution of existing migrants become increasingly important in determining the future patterns of urbanization. Urban agglomerations (UAs) have long been the major destination of China's internal migration. They are also appointed as the main form of future urbanization in the recently released national planning of new-type urbanization. Five major UAs were selected as a case study, including three coastal ones, namely the Yangtze River Delta (YRD), the Pearl River Delta (PRD), and the Beijing-Tianjin-Hebei region (BTH), and two inland ones, namely the Middle Yangtze River (MYR) and the Chengdu-Chongqing (CC) region. Based on data of the latest population census and the dynamic monitoring survey of floating population in the five major UAs, this paper first examined the spatial patterns of in-migrants from multiple dimensions of destination, origin, and distance of migration. The trends and urbanization effects of migration on the destination and origin were then assessed by comparing the settlement and hukou transfer intentions of migrants with different origins and destinations. The results showed the coexistence of common and distinct features in these mega regions. Although the continuous attractiveness of central cities for migrants was observed in all regions, peripheral cities in the YRD and PRD have become increasingly attractive as well, leading to a moderately dispersing trend in these two pioneering coastal UAs. Moreover, the concentration level and spatial distribution of migrants among cities were generally stable in the YRD and PRD but continuously adjusting in the BTH and two inland UAs. The fastest growth was found in inter-county migration within province and the slowest in intra-county migration. The coastal UAs were strongly preferred by inter-provincial migrants, while the inland ones could only attract migrants from the same or surrounding provinces. Despite this, significant distance attenuation was found in all of them. In terms of the origins of migrants, those from central provinces had flowed mainly to the YRD and PRD, whereas those from the northeast showed a high preference for the BTH region. We can anticipate the future patterns of migration and urbanization from the settlement intentions of migrants from and to different cities. From the destination view, the advantage in public services made central cities considerably more attractive than other cities. Hence, they are expected to be continuously faced with severe contradiction between supply and demand of public services. In the inland UAs, however, central cities and ordinary ones are able to share the pressure of public service provision. From the original view, the high-quality and equally accessible public services are important for inland regions to attract return migrants, and providing high possibility for the return-migration-induced urbanization. However, the population loss in the northeast may become a long-term trend that can hardly be reversed in the visible future.

The water-food-energy nexus (WFE) plays a key role in achieving sustainable development. In this study, we systematically analyzed the concept of the WFE nexus and review its recent progress. We found that the academic communities have not reached a unanimous understanding of the concept of the WFE nexus and research framework. The evaluation methodology of the WFE nexus presents a transition from the traditional sectoral research paradigm to the human-environment system paradigm that considers the intersection of natural science and social science. These methods can also be grouped into three categories: an evaluation based on a critical process, an evaluation based on the whole system, and a comprehensive evaluation that involves coupling the internal and external elements of the WFE nexus. A bibliometric analysis shows that the number of research papers concerning the WFE nexus increased exponentially during 2000 to 2019, and the increase was particularly significant after 2015. Environmental science, food science, and nutrition science are the three main disciplines in WFE nexus research. More important, we need to strengthen the application of geography thinking, that is, comprehensive and systematic thinking, to study the WFE nexus in the future. Based on the literature review, we found that existing research lacked a quantitative understanding of the mutual feedback among the WFE nexus and its evolution. Therefore, we suggest the following five priority areas for future research: establishing a multi-source database of the WFE nexus, revealing the mutual feedback mechanism of the WFE nexus, developing a coupling model of the WFE nexus, establishing a decision-making platform for the WFE nexus, and promoting the collaboration of multiple sectors related to the WFE nexus. This will help to achieve a synergetic sustainable development of the WFE nexus through system governance and scientific management.

Eliminating inequality and achieving balanced development is one of the Sustainable Development Goals of the United Nations. Accurate measurement of development equilibrium is a primary scientific problem to be solved urgently. Nighttime lights data have been proven to be a good proxy for economic activity, and they have been used widely due to their advantages of convenient acquisition and wide spatial coverage. Therefore, in this study, we applied the Gini coefficients derived from nighttime lights data and pixelized population data to evaluate the development equilibria for China's 2900 counties from 2002-2020. We then examined the nexus of the development equilibrium and developmental vitality represented by the average nighttime lights intensity within each county. The results showed that the Gini coefficients based on nighttime lights data have generally been decreasing for 96% of the counties in China during 2002-2020. Moreover, in general, the Gini coefficients present a spatial pattern of being lower in the east and higher in the west. The results illustrate the synergetic development pathways of economic growth and equilibrium promotion of the economically developed counties, although the variation of their equilibria is significant. On the contrary, there is still distinct room for improvement of development equilibria for 60% of the economically underdeveloped counties in China. The results provide scientific support for achieving balanced development and promoting common prosperity in China.

County is the pivotal platform and region unit to realize the new-type urbanization. The study of county-level CO₂ emissions is of great significance to improve China's urbanization strategy, accelerate the achievement of ecological civilization and low-carbon transformation. Based on the data of China's county-level CO₂ emissions from 2000 to 2017, this paper analyzed the overall tendency, regional differences, spatiotemporal pattern and agglomeration characteristics of per capita CO₂ emissions. Meanwhile, under the STIRPAT model and EKC hypothesis, this study employed the panel quantile regressions to explain the dynamic impact of socio-economic development on per capita CO₂ emissions. The main conclusions show that: (1) China's county-level CO₂ emissions show an increasing trend of rapid growth followed by slow growth. The regional disparity of per capita CO₂ emissions is distinct and shows a more uneven trend. (2) On the whole, China's county-level CO₂ emissions present a spatial pattern of "high in the north and low in the south". The per capita CO₂ emissions level in economically developed areas is much higher than that in other areas, thus brings about an obvious spatial polarization effect. (3) There is a significant positive spatial correlation of per capita CO₂ emissions within counties. The number of counties with High-High concentration gradually increases and the distribution center gradually moves to Northwest China, while the number of Low-Low concentration counties decreases continuously and they were mainly distributed in the central and southern regions. The agglomeration type of county-level per capita CO₂ emissions presents a spatial locking effect. (4) Population density and government expenditure have an inhibitory effect on county-level per capita CO₂ emissions, while the scale of secondary industry output value and carbon emission intensity have significant promotive influence. And there is an inverted "N-shaped" relationship between economic development and per capita CO₂ emissions in the counties with low- and middle-level emissions. The adjustment of socio-economic development structure plays a critical role in achieving China's total CO₂ emission reduction target. Therefore, the policy makers of emission reduction strategy should consider the regional disparity to realize the development and transformation of backward counties. And the key urban agglomerations should play a leading role in carbon emission reduction simultaneously. In addition, improving energy use efficiency through technological innovation should be the key way to the reduction of carbon emissions in China's counties at the present stage.

The diurnal freeze-thaw cycle of near-surface soils on the Qinghai-Tibet Plateau (QTP) significantly affects the exchange of water and energy between the soil and the atmosphere, which is important for an understanding of the response of the QTP to climate change. Based on MODIS, AMSR-E and AMSR-2 data, we first obtained the diurnal calibration coefficients from AMSR-2 to AMSR-E in the Qinghai-Tibet Plateau (QTP), and then used the Fourier nonlinear model to fusion diurnal freeze-thaw index with surface temperature, and further obtained the diurnal freeze-thaw condition of near-surface soils at 1 km resolution per day, and finally carried out a study on the spatial and temporal changes of diurnal freeze-thaw cycles of near-surface soils in the QTP between 2002 and 2020. The results indicate that: (1) The improved calibration method of AMSR series sensors in this paper is more suitable for the QTP region than the calibration method for global scale. The accuracy of the freeze-thaw product obtained by fusion using the Fourier nonlinear model was 80.96% for diurnal freeze-thaw discrimination, which was 3.95% higher than that of the unfused product. (2) The frequency of diurnal freeze-thaw cycles in the seasonal freeze-thaw process of near-surface soils on the QTP varies spatially, with the highest frequency occurring in the southern Tibetan region and the Qinghai plateau, and is cyclical in time, the high frequency region shows a shift to the northwest when warming and to the southeast when cooling. (3) In the past 20 years, the trend of diurnal freeze-thaw days in different parts of the QTP is varied, with the northern Tibetan plateau, southern Tibetan alpine region and eastern Tibetan region showing an increase and the Qinghai plateau showing a decrease. (4) There are regional differences in the beginning of the continuous diurnal freeze-thaw cycle on the QTP, with the beginning of the thawing process being gradually delayed from east to west and the beginning of the freezing process being gradually delayed from west to east. In the past 20 years, the starting time of continuous diurnal freeze-thaw cycle in near-surface soils has been changing, with 0.17 d/a earlier during thawing and 0.18 d/a earlier during freezing.