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.

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.

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.

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.

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.

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.

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.

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.

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.

Water retention plays a critical role in terrestrial ecosystem service. However, regarding its definition and calculation, there is a long debate in academia, which illustrates its importance in practice, and simultaneously demonstrates the complexity and vagueness of this essential concept. Thus, there is an urgent need to clarify its definition and calculation method based on basic ecological and hydrological theories, and eventually promote science-based decision-making and integrated water management. Interestingly, we observed that for the same term of "water retention function", ecologists intended to concern the terrestrial ecosystem's water storage capacity (S_max), while hydrologists concerned more about the water yield from the catchment (Q). Both perspectives have their own rationality, but with totally different vision and emphasis. By theorical discussion and data analysis, we found that water storage capacity (S_max) and water yield (Q) indeed have strong connection, but they are definitely two different concepts. The S_max of terrestrial ecosystem determined the separation of precipitation into either evaporation (green water) and Q (blue water). The size of S_max in most cases trades off with the amount of Q. We further revealed that the root zone storage capacity (S_Rmax) of ecosystem is at the heart of water retention function assessment, and plays a key role linking blue and green water. The S_Rmax is the result of ecosystem's adaption to its climate, and can be derived by the classic method to design reservoir, i.e. the Mass Curve Technique (MCT). Lastly, we gave three recommendations: (1) simultaneously evaluating green water retention capacity and blue water yield in practice; (2) further investigating the water retention functions of more water bodies, e.g. glacier, snow cover, and groundwater; (3) synergizing natural and artificial water retention capacities to enhance the water use efficiency in both the ecosystem and our economic-social system.

According to the strategic direction of urban-rural integration and rural revitalization, the spatial reconstruction of rural settlement system is the spatial organization foundation of future urban-rural integration development. This paper focused on the hierarchical scale and spatial organization characteristics of the rural settlement system. It comprehensively revealed the evolution process and regional characteristics of rural settlement systems of 111 administrative units in Guangdong province from 1990 to 2020, and discussed their evolutionary mechanism and spatial optimizing and reorganizing regional modes. The results show that: (1) There were significant regional differences in the hierarchical scale distribution of the rural settlement system in Guangdong. The patches of rural settlements show the characteristics of concentric aggregation and distribution centered on the geometric barycenter of each administrative unit. The spatial distribution pattern of the rank cumulative size coefficients of rural settlement system was "high in the southwest, but low in the northeast" and "high in coastal areas, and low in the inland". The decreasing region of the rank cumulative size coefficient was concentrated on the east bank of the Pearl River Estuary and coastal areas of eastern Guangdong, while the increasing region was mainly distributed on the west bank of the Pearl River Estuary. (2) The influencing factors such as natural background, economic development, urbanization development, transportation and location, institutions and policies jointly drove the development and evolution of the rural settlement system. Rural settlement system of urban areas is small in scale in the mature stage of urbanization, which will gradually die out and integrate into the city. Driven by urbanization, industrialization and policies, rural settlement system of suburban areas has experienced survival of the fittest and maintains a stable scale, but the mixed distribution of urban and rural land makes the spatial organization of rural settlements increasingly loose. Driven by the continuous outflow of production factors, exurb rural settlements appear to be "hollowing out". The villagers returning to build new houses and the lack of homestead exit mechanism have led to a continuous and stable growth in rural settlement scale, and their spatial distribution is characterized by more peripheral diffusion. Rural settlement system with poor location in mountainous areas develops slowly under the support of policies, and the aggregation characteristic along the transportation line is significant. (3) Facing the integrated development of urban and rural spaces, four models of spatial optimization and reorganization of rural settlement system are proposed: urban-rural integration development, dual-core-driven development, central place hierarchical system development, and pan-center chain-connecting cluster development.

Subsurface stormflow is a special form of subsurface flow in the vadose zone of steep slopes in mountainous and hilly regions, and it is also one of the most important runoff generation mechanisms in the process of flash flood formation. However, the systematic summary on the scientific connotation, mechanisms, and disaster-causing characteristics of the subsurface stormflow in current research is very rare and this limits the development of the theoretical system of runoff generation, routing, and modeling methods of flash floods. Herein, we clarify the scientific connotation and definition of subsurface stormflow based on the division of the development periods of the subsurface stormflow research around the world as well as the analysis of physical processes for the runoff generation. Meanwhile, three physical conditions for the occurrence of subsurface stormflow, together with their influences on the nonlinear response process, are highlighted. The influences of the subsurface stormflow on the dynamic development of flash floods, landslides, and debris flow hazards are analyzed and summarized. Finally, three key research directions are proposed: water transport processes and hydrological connectivity mechanism of the macropores in the vadose zone, processes and mechanisms of water exchange at the geotechnical channel interfaces inside the slopes, and the formation mechanism for flash flood from multiple runoff generation processes with complex slope topography conditions. This work can provide new research perspectives for the formation mechanism and hydrological theoretical framework of flash floods in complex mountainous regions, and better support the national scientific and technological needs for flash flood forecast as well as disaster prevention and mitigation.

Soil organic carbon (SOC) storage and soil carbon sinks play a crucial role in the global carbon cycle of terrestrial ecosystem. However, many previous studies of soil carbon storage and sinks utilized low-resolution land use dataset, with limited focus on soil carbon sinks from farmland and grassland management. To address this issue, this study employed a series of accounting models to estimate the carbon sink from farmland and grassland management, the carbon sink from forest management, changes in soil carbon storage, changes in carbon storage due to land use conversion from 2000 to 2020, as well as the soil carbon storage in China in 2000 and 2020 using a 30 m-resolution land use dataset. The results showed that the national carbon sink from farmland management in China was approximately 17.918 Tg C a^-1 and the carbon sink from grassland management was approximately 20.171 Tg C a^-1 during 2000-2020. The carbon sink from forest management in China was approximately 81.622 Tg C a^-1 during 2000-2020. The soil carbon storage (0-100 cm) in China increased from 86.074 Pg C in 2000 to 86.771 Pg C in 2020. The soil carbon storage increased by approximately 34.850 Tg C a^-1 from 2000 to 2020. The land use transformation during the study period resulted in a decrease of approximately 17.621 Tg C a^-1 in soil carbon storage. The findings of this study can help researchers understand China's carbon storage and provide scientific data to China's 2060 Carbon Neutrality Target.

The variation of land surface temperature (LST) has a vital impact on the energy balance of the land surface process and the ecosystem stability. Based on MDO11C3, we used methods including regression analysis, GIS spatial analysis, correlation analysis, and center-of-gravity model, etc., to analyze the LST variation and its spatiotemporal diversity in China from 2001 to 2020. Finally, the Geodetector was used to identify the leading factors of LST variation in 38 eco-geographical zones of China, and explore the causes of its pattern. The results show that: (1) the average LST in China from 2001 to 2020 is 9.6 ℃, which is high in the plains, and low in the mountainous areas. Generally, LST has a striking negative correlation with altitude, with a correlation coefficient of -0.66. China's First Ladder has the most conspicuous negative correlation, with a correlation coefficient of -0.76 and the lapse rate of LST is 0.57 ℃/100 m. (2) The change rate of LST in China during the study period is 0.21 ℃/10 a, and the warming area accounts for 78%, showing the spatial characteristics of "multi-core warming and axial cooling" in general. (3) LST's variation has prominent seasonal characteristics in the whole country. The spatial distribution of average value in winter and summer is quite different and fluctuates obviously; the moving trajectory of the centroid in the warming/cooling area is close to a loop shape. The movement direction shows the corresponding seasonal reverse, and the movement range in the cooling zone is larger, indicating that the regional difference and seasonal variability of the cooling zone are more obvious. (4) China's LST variation is driven by natural conditions and human activities, of which natural factors contribute more, with sunshine hours and altitude being the key factors. The boundary trend between the two dominant type areas is highly consistent with the "Heihe-Tengchong Line". The eastern region is mostly dominated by human activity intensity and interacts with terrain factors, while the western region is dominated by natural factors, which enhance/weaken the change range of LST through mutual coupling with the climate, terrain, vegetation, and other factors. This study can provide scientific references for dealing with climate change, analyzing surface environmental models, and protecting the ecological environment.

Global climate change caused by human activities results in frequent extreme climate events, and shifts the physiological processes of plants, and the carbon, water cycle and energy balance of terrestrial ecosystems. Vegetation phenology is the most sensitive biological indicator to climate change. In recent years, the responses of vegetation phenology to climate change mainly focus on the mean state of the climate, while the response mechanisms of vegetation phenology to extreme climate are still unclear. In this paper, the response of vegetation spring and autumn phenology to various extreme climatic events and their mechanisms were reviewed. We found that extreme low temperature and extreme precipitation directly delayed the vegetation green-up date and advanced the leaf senescence, while extreme high temperature and extreme drought led to stomatal closure, inhibited photosynthesis and transpiration, and thus advanced leaf senescence at middle and high latitudes of the Northern Hemisphere. Currently, the studies on the response of vegetation phenology to extreme climate events pay less attention to compound extreme climate events, and there are only few studies on the lag effect of vegetation phenology response to extreme climate events and the recovery process of vegetation after the occurrence of extreme events. Under future climate change scenarios, it is necessary to modify the vegetation phenological models by considering the impact of extreme climate events and couple it into the dynamic global vegetation models to improve the simulation accuracy of the carbon cycle in terrestrial ecosystems.

The study of the new economic geography has paid attention to the polarization and balanced development of urban systems. In reality, however, transport accessibility is subject to great uncertainty in explaining the polarization and balance of the urban system. In fact, the polarization or equilibrium of the regional urban system is not only unique in China, but also a general phenomenon in countries with different development outcomes, political systems and degrees of marketization. From the perspective of industrial heterogeneity, this study empirically analyzes the process and mechanism of the industrial structure of regional central cities on the population growth of neighboring cities in China from 1980 to 2020, and examines the influence of industrial structure on the polarization and equilibrium development of the regional urban system. The results show that, firstly, the manufacturing sector strengthens the spillover effect from the core city and promotes the population growth in neighboring cities, while the service sector weakens the spillover effect and hinders the growth in neighboring cities. Secondly, the manufacturing-oriented cities have relatively small city scale, while the service-oriented cities are relatively large. Therefore, the driving effect of manufacturing-oriented central cities on the neighboring cities is larger, which tends to produce a relatively balanced regional city system. Correspondently, the spillover effect of service-oriented central cities on the neighboring cities is smaller, which tends to form a relatively polarized regional city system. Finally, as the share of services in the industrial structure of central cities continues to rise, China's urban system may become more polarized rather than balanced. Certainly, the higher the proportion of manufacturing in the central city, the more balanced the regional urban system is. In fact, the empirical results show that the industrial structure and the spillover effect of the core city have an inverted U-shaped relationship, i.e. a high proportion of manufacturing or services weakens the driving effect of the core city on surrounding cities. The reasons for this vary. The high proportion of manufacturing and the small size of the central city have a limited spillover effect on the neighboring cities and therefore can hardly drive their growth; while the high proportion of service industry and the negative effect of the service industry on the spillover effect lead to the slow development of the neighboring small-and-medium-sized cities. It is worth noting that because of the significant spatial impact of industry on the urban system, the future regional urbanization strategy should be coordinated with the industrial strategy. More importantly, with the gradual liberalization of the household registration system, industry selection can become an effective policy option for macro-control of the regional urban system.

It is a hot issue in climate change research to study the response mechanism of mountain snow cover to climate warming based on elevation-dependent warming. Based on Terra Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover phenology datasets from 2000 to 2019, we analyzed the spatiotemporal variation of snow cover days in the north and south of the Qinling Mountains by the methods of trend and detrended correlation analysis. Meanwhile, we identified the influencing factors of snow cover days from the perspectives of sea surface temperature (SST) in autumn and winter of the equatorial Pacific, high pressure over the Qinghai-Tibet Plateau, respectively. The results are as follows: (1) after 2013, climate condition in the north and south of the Qinling Mountains shifted from "warming hiatus" to "warming up", followed by declining snow cover days. And the proportion of areas with snow cover more than 10 days decreased from 35.1% to 8.6%. (2) We identified 1950-2000 m in the Qinling Mountains and 1600-1650 m in the Daba Mountains as transition zones of snow cover days. Above the transition zone, the increasing rate of snow cover days with altitude is higher than that of the low altitude area. Particularly, the altitudinal belt between 2100 m and 3150 m is the sensitivity zone of snow cover days to climate change. On the basis of the reference period of 2000-2004, we find that the elevation with 40, 60 and 80 days of snow cover increased by 100 m, 100 m and 150 m for the period of 2015-2019. (3) The SST in autumn and winter over NINO C and NINO Z regions and the winter high pressure over Qinghai-Tibet Plateau are two effective indicators of snow cover days anomaly in the Qinling Mountains, Hanjiang Valley and Daba Mountains. The lower SST of the central equatorial Pacific in autumn and winter, or the lower the winter high pressure over the Qinghai-Tibet Plateau is, the more excessive snow cover days would occur. (4) In terms of circulation mechanism, during the years with more snow cover days, the 0 ℃ isotherm in January and February was southerly, providing the proper temperature for increasing snow and ice accumulation and delaying snow and ice melting. Moreover, there was a weak water vapor convergence zone in January, which provided water vapor conditions for increasing snow and ice accumulation. The findings can enrich our understanding of winter climate change and provide early warning information of snow anomaly in the subtropical and warm-temperate zones in China.

Understanding the characteristics of transnational migration in Asia is beneficial for China to formulate a reasonable international migration policy in the new era and promote the high-quality development of the Belt and Road Initiative. Based on the data of bilateral international migration flows from 1990 to 2015, this study tries to clarify the temporal and spatial patterns and influencing factors of Asian transnational migration by using social network analysis and spatial filtering panel negative binomial gravity model (ESF). The results are listed as follows: First, the main migration flows in Asia from 1990 to 2000 were concentrated in West Asia, South Asia and Southeast Asia, and most of them occurred between the adjacent countries and regions. From 2000 to 2015, there was a number of large-scale migration flows across the above three subregions. Second, the scale of the migration network in Asia is relatively low, and the degree of closeness between the Asian countries has increased first and then weakened over time. Third, political instability and war conflicts of the origin were important driving forces for transnational migration in Asia. Besides, the differences of economic development and national income between countries were the crucial driving forces, while multi-dimensional proximity factors played an important role in promoting transnational migration. Fourth, from 1990 to 2015, the effect of economic differences on transnational migration increased first and then weakened. In addition, political instability has always been the main influencing factors for migration. Besides, the development of import trade has positively promoted transnational migration, and the attractiveness of studying abroad has a fluctuating effect on transnational migration. Finally, non-economic and structural impacts were the most important factors influencing the transnational migration in Asia.

The shipping service industry is a major driving force in the economic growth and reorganization of port cities' spatial structure, as well as a core element in raising hub port cities' competitiveness. Recently, the global distribution and network connections of the shipping service industry have attracted significant attention, but few studies have analyzed the distribution differences and influencing factors of different shipping service industries. In this study, we divided the shipping service industry into upstream shipping auxiliary industries (ship owners, ship management, ship repair and construction) and downstream shipping derivative service industries (shipping finance, shipping insurance, maritime law). And based on Lloyd's Maritime Directory in 2019, we built a database about the world's shipping service industry. The spatial connection network of the global shipping service industry was then examined at the global, regional and city levels, using the correlation network model and the negative binomial regression model, which revealed the differences in distribution between the upstream and downstream shipping services. The affecting elements on upstream and downstream shipping services are explored in the last section. The results are as follows: (1) Europe and Asia are the primary distribution region of the upstream and downstream shipping service industries, a pyramid structure is shown under the variation in countries' distribution. The spatial distribution of the upstream industry is wider in range, closer in connections and stronger in agglomeration, compared to the downstream industry. (2) The global shipping service network presents a dual-center structure. Europe centers on London and builds a trans-continental radiation network of downstream shipping derivative services connecting to neighboring capital cities. Asia forms an upstream service network that connects Hong Kong, Shanghai and other cities with Singapore as the center. (3) The upstream shipping auxiliary industry is mainly distributed in non-capital seaport cities, while the downstream shipping derivative service industry is chiefly distributed in the capitals and other administrative centers. (4) The e-commerce index and the logistics performance index are positively related to the upstream and downstream industries. Otherwise, the upstream shipping auxiliary industry is also affected by the degree of economic freedom, the number of tourist arrivals, and the liner transport index, while the downstream shipping derivative service industry is mainly influenced by international trade and political culture. This study provides a theoretical reference for China to construct an international shipping center, reaches the linkage development between upstream and downstream shipping services, and improves the overall strength of China's shipping industry.

Economic globalization has reshaped the world economy's spatial pattern while simultaneously changing the context for developing economic geography theories. This study revisited the changing features of economic globalization and investigated its geographical implications. Next, it summarized the new trends in economic geography studies in response to the changing economic globalization. Lastly, this study proposed a research agenda for domestic economic geography studies by combining the requirements of global trends and national strategies. The main findings include the following: The scale of geographical integration during economic globalization keeps shrinking, leading to a pattern of regionalization. The driving forces of economic globalization have gradually shifted from cost-saving to innovation. Accordingly, the benefits of economic globalization will be reallocated between developed and developing countries. The trade-offs between efficiency and resilience alter the global value chain, shifting outsourcing from off-shoring to re-shoring or near-shoring. The changing economic globalization has witnessed the rising effects of geographical distances, institutions, and resilience on increasing the inequality of the global economic geography. In economic geography, the scalar structures shifted from the global-local to the global-national-local. The relational networks evolved toward a multi-level, multi-agent, and multi-scale one. The role of the nation has been revisited. More attention has been paid to geopolitical hotspots. Overall, economic geography's institutional, cultural, relational, and evolutionary turns exhibit an emerging trend to convergence. In such a setting, domestic economic geography should find a new balance between global trends and national strategies. This study proposed seven research issues, including: (1) the practice of the Belt and Road and the pattern of inclusive globalization; (2) the economic geography of dual circulation; (3) the paths and resilience of regional development in response to the global production network restructuring; (4) the evolution and competitiveness of industrial clusters; (5) the building of multi-level innovation systems; (6) the regional sustainable development within the global environmental governance system; and (7) the impact of geo-economics on national economic security and interests.