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.

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.

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.

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.

Ladakh is located in the northwest of the Qinghai-Tibet Plateau, the western section of the Himalayas, and the upper reaches of the Indus River valley. It is now part of Indian-controlled Kashmir. Since ancient times, Ladakh has been the "key point" from northwest South Asia to the Ngari Prefecture of Xizang and southern Xinjiang. However, most existing research on Ladakh focuses on its local history and culture. Although there are some related works on geopolitical relations, few have studied the historical changes of this region and its subordinate relationship and geographical value with China over a long time scale and analyzed the geographical significance of Ladakh. At the same time, some erroneous views and geographical maps have been disseminated on the Internet at home and abroad, which urgently needs a comprehensive correction from the academic level. Based on a variety of historical documents, map data, and a detailed review of previous research results, this paper demonstrates the changes in place names, historical evolution, and regional scope of Ladakh from the 1st to the 21st century and analyzes its significance in the homeland security of western China. The results show that: (1) As the native land of China's Xizang Ladakh was part of the Tubo Dynasty until the 9th century. After the collapse of the Tubo Dynasty in the middle of the 9th century, Ladakh was an essential part of the Ngari local administration established by the descendants of the Tubo Royal family. In the 13th century, Ladakh was again united within the territory of China's Yuan Dynasty and continued through the Ming and Qing dynasties. It remained until the mid-19th century when the Prince-state of Jammu in southern Kashmir invaded it and incorporated it into the British Indian colony. It was then occupied by the Indian army in 1947. (2) Ladakh region has a tortuous history with many changes in place names. However, when Jammu annexed it in modern times, Ladakh only referred to the upper reaches of Indus Valley between the Western Himalayas and the Karakoram Mountains, with Leh as the center. (3) The complexity of the historical and geographical processes in the Ladakh region makes it the central area of conflicts created by India in the western section of the China-India border. Therefore, China should adopt active strategies to avoid India's continuous "assimilation" policy.

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.

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.

The Tibet Plateau and the Hengduan Mountains are located in the southwest of China, being featured by intricate landforms and deep valleys with large slopes. Due to the impacts of fluvial-induced erosions and intense geologic processes, frequent occurrences of geological disasters such as landslides, collapses and debris flows can be observed and are challenging regional sustainable development. Here we developed a random forest (RF) model to identify the geological disaster points within each sub-region. We found that the accuracies of RF models in sub-regions were all larger than 80% and can reach 91%, which evidenced modelling performance of the developed model in this study in identification of the locations with frequent occurrences of geological disasters. Meanwhile, the locations and/regions with frequent occurrences of geological disasters were found mainly in the southern part of the Hengduan Mountain area, and northeast and south parts of the Tibet Plateau, where 87% of all disaster events ranged from small scale to middle-scale. Specifically, from the view of sub-region, areas with frequent occurrences of geological disaster were 17.5 \times {10}^4km², 17.4 \times {10}^4km² and 27.5 \times {10}^4km², respectively. Due to the spatial heterogeneities of landforms, climatic conditions and disturbance intensities from human activities, major causes of geological disasters (without considering classes of geological disasters) vary from sub-region to sub-region. For sub-region Ⅰ (south part of the Hengduan Mountain area), the main driving factors behind the small-scale and middle-scale geological disasters are impacts from constructions of roads and vibration from transportation (attribution ratio (AT) as 20.2%). Besides, main driving factors behind the small-scale and middle-scale geological disasters for both sub-regions Ⅱ~Ⅲwere impacts from vegetation coverages on slope stabilities, whose ATs are 23.6% and 27.3% respectively. Besides, the second most important causes behind small-scale and middle-scale geological disasters for sub-regions Ⅱ~Ⅲ were impacts from constructions of road and transportation (AT as 15.7%) and impacts from river erosions on slope stabilities (AT as 17%) respectively.

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 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.

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.

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.

Based on registered population data, this paper examined a variety of population density models to explore the spatio-temporal pattern of the registered population of Nanjing during the past century. The results showed that: (1) The number of registered residents in Nanjing from 1928 to 2017 showed a flat "S"-shaped growth trend, forming an extensive dispersion with localized concentration types. The population density was the greatest in the Qinhuai River area, which has been the main registered population center. (2) The spatial structure of the registered population included: point-single center, axis-double center, enclave compound-multi center, and radiation-circle polycentric center. (3) The polycentric model, which is based on the central place theory, provided the best explanation for the features of the spatial structure of the registered population. The registered population distribution pattern in Nanjing was attributed to the joint action of four spatial location rules: the distance-decay law, allometric growth effect, spatial polarization characteristic, and regional-edge structure. (4) The transitions in the city during the past century were not a de-urbanization but a temporary fluctuation because of social transformation. Notable differences remained between traditional-Chinese residential center and the central business district.

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.

Administrative division is an important part of the national governance system. A systematic analysis of the spatial and temporal change pattern and influencing factors of the adjustment of county-level administrative divisions in the Qing Dynasty can better learn from and give play to the supporting role of administrative divisions in national and local governance. Using the textual research results of the national Qing history compilation project Qing History·Geographical Chronicles, and referring to the Qing Dynasty archives in China's first historical archives collection, Qingshilu, Qinghuidian, Daqingyitongzhi, local chronicles and other historical documents, this paper comprehensively analyzes the overall evolution and adjustment of county-level administrative divisions from 1683 to 1911. The research shows that: (1) There are 9 kinds of adjustment forms of county-level administrative divisions in the Qing Dynasty. The key of the adjustment is the proposal power of the governor, and the governor system is the institutional guarantee for the adjustment and promotion of administrative divisions. (2) The frequency of administrative division adjustment was greatly affected by the governance concept of the supreme ruler, showing fluctuating changes. The Yongzheng period was the absolute peak of administrative adjustment in the Qing Dynasty, the Guangxu and Xuantong periods was a relative peak, and the adjustment of Daoguang to Tongzhi periods was the least. (3) The setting of county-level administrative divisions was the most frequent, followed by the change and splitting of subordinate relations. Level change and consolidation were 2 types with lower adjustment frequency. (4) In the Qing Dynasty, the 4 types of adjustments of upgrading, relocation, abolishment and new establishment were widely distributed in 23 provinces, with the highest uniformity of provincial distribution, and the 4 types of adjustments of renaming, merging, changing affiliation and changing at the same level were concentrated in provinces such as Zhili, Henan and Shanxi. (5) The formation of the adjustment pattern of county-level administrative divisions in the Qing Dynasty was the result of the joint action of many factors. Political consideration was the decisive factor. All this reflected the management concept of clear hierarchy, clear rights and responsibilities, adjusting measures to local conditions and step by step.

The quality of development is crucial for China to comprehensively build a socialist modern country. Drawing on related concepts of development in quality, the paper conceptualizes a city in high-quality development and proposes a stylish framework with five dimensions to evaluate it, in line with the New Development Philosophy, which is composed of innovation, coordination, greenness, openness and sharing. Using the methods of spatial analysis, club convergence test and spatial Durbin model, the paper identified the spatial evolution of the quality of city development in China and associated determinants during 2005-2020. On average, the level of city development quality increased by 48.4% during the study period. The number of cities at low-level of quality in development decreased dramatically, accompanied by a profound transformation in the spatial pattern of city development quality, which presents significant spatial aggregation. The spatial imbalance remains for cities with different development qualities, and the challenge is still huge to narrow the gap. With significant role differentiation among cities, a "pioneering-catching up" pattern emerges, and the 11 pioneering cities such as Beijing, Shanghai and Shenzhen have become the pioneers of high-quality development in China. Key determinants for cities achieving high quality in development includes urbanization level, public investment, digital economy, environmental regulation and economic growth, while there is inverted U-shaped relationship between city size and development quality. To achieve the goal of high-quality city development in the new era, it is necessary to focus on the development of cities in the central and western regions, making full use of the demonstration role of pioneers, promoting quantitative growth, strengthening environmental regulations, cultivating the new forms of digital economy, and optimizing the city size hierarchy.

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 history of Chinese economic geography as a research field is virtually an evolution of ideas on the relationship between economic activities and geographical environment. In ancient times, the idea on adapting to geographical conditions to cultivate economic activities had emerged, and numerous cases of regional practices were recorded in local chronicles. In the period from 1840 to 1948, economic geography appeared as a scientific discipline, and relevant research on agricultural and industrial geography was carried out. In the period from 1949 to 1978, the ideas on economic geography of the Soviet Union were fully introduced, with research focusing on the use of natural conditions and resources, and on the relationship between production distribution and geographical contexts to meet the national needs of economic development. In the period from 1979 to 2000, starting from territorial management and land planning, the important perspective formed on the relationship between man and land, and the theoretical progress was made in the establishment of Point-axis Concept and other spatial structural patterns. Economic geographers also made proposals on government regulations based on an expanding trend of regional differences. In the period from 2001 to 2020, one of the foci related to the relationship between man and land was the major fuction-oriented zoning, and other hot topics included issues of industrial agglomeration, urban economic zones, rural revitalization, and the impact of new factors on formation mechanism of the spatial structure of economic activities. The development of Chinese economic geography thought can be sorted into three threads. The first one is the long-lasting records that consist of rich historical documents, from the description of a large number of economic locations and differences of their geographical contexts, to the exploration of the relationship between economic activities and geographical environment. Together with a large number of local chronicles, the idea of man-land relations was hidden in the text. The second thread is the trajectory of travel notes which was developed into modern investigations and observations, providing important means of discovering scientific facts for the study of economic geography. The third thread is the introduction of ideas from other countries including investigation techniques, research methods and thinking logic, which further promotes the development of China's economic geography. The survey on the history of economic geography ideas can provide three enlightenments for further study of economic geography: (1) strengthening the exploration of the relationship between economic activities and the geographical environment; (2) encouraging problem-oriented critical thinking; (3) improving the weaknesses of China's economic geography research, such as the reduction theory and the deductive method.

With the progress of holistic science and human society, development of geographical sciences has entered a new stage of interdisciplinary integration. Under this context, geographical sciences urgently needs to seek new paths through the deep integration of disciplines to better improve the knowledge system and contribute to the country and society development effectively. Based on the perspective of the National Natural Science Foundation of China (NSFC), this paper firstly deeply analyzes the current status and problems of the integration and development of geographical sciences in China, and points out that it is not fully integrated with the frontier of international geographical sciences, and the global political, economic and cultural influence of geographical research in China needs to be strengthened; considers that the ability of Geographic Sciences integrating national major practical needs for theoretical and technological innovation should be improved; suggests that the internal discipline system of geographical sciences in China should be further optimized according to the needs of knowledge integration. Then, this paper proposes three paths for the integrated development of geographical sciences under the guidance of funding policies, that is, the interdisciplinary integration facing the frontiers of science and technology in the world, the multiple fields integration facing the major national development strategies, and inner-discipline integration facing the optimized application codes of NSFC. In future, based on maintaining the continuity and stability of the development of disciplines, the NSFC will encourage the integration of geographical sciences with other disciplines and fields through the improvement and innovation, so as to promote and build a healthier and more innovative 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.

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.

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.

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.

Designing and building up the natural resources surveying and monitoring technological system (referred to as the "Technological System") is an important measure to establish and improve the natural resources management, promote the intensive and economical utilization of natural resources, and harmonize the coexistence between man and nature. It is a geo-science related research project with many complicated factors and challenging tasks. Following the mandates and requirement of the unified natural resources surveying and monitoring, the paper firstly analyzes the basic problems in designing and building up the "Technological System" from the holistic characteristics of the surveying and monitoring process and the systematic characteristics of its engineering implementation. A comprehensive overall framework of "Technological System" is resulted and discussed. Then the development direction of "Technological System" is proposed and analyzed, including the collaborative data sensing, automatic information processing, elaborative natural resource scene modeling and management, as well as intelligent knowledge service. Then the article discusses the digital-intelligent realization path of the "Technological System" to meet the advanced and practical requirement. It has led to the formulation of the future research agenda with five major research and development tasks, including the development of space-sir-ground-ocean-web collaborative sensing network system, construction of automatic information processing platform, spatio-temporal scene modeling of natural resources, development of spatio-temporal knowledge service of natural resources, and reconstruction of engineering technical flow. In the future, it is necessary to strengthen the strategic needs analysis, enhance key technologies innovation and promote interdisciplinary collaboration in order to effectively build up the "Technological System" and promote its operational application.

The Yellow River Basin (YRB) has been facing severe water shortages, hence the monitoring of long-term dynamics of surface water area (SWA) is essential to better understand the spatial and temporal variation of surface water resources and its driving factors. In this study, the spatial and temporal change characteristics of SWA in the YRB were revealed, and then the impacts and relative impact rate of precipitation (Pre), temperature (Temp), leaf area index (LAI), SWA in the previous year (Pre_SWA) and residual factors (e.g. water conservation measures and human water use activities) on SWA were determined in the combination of water detection index, linear slope, multiple linear regression and partial differential decomposition. The results show that: (1) the overall accuracy of classification of surface water bodies is 97%. The increase rate of year-long SWA in the study area from 1986 to 2019 is 49.82 km²/a, of which 83.2% was contributed by the SWA increment from the main river channel area, and the year 2001 is the turning point of SWA trend from decreasing to increasing; the seasonal SWA decreased at a rate of -79.2 km²/a, of which 61.8% was contributed by the SWA decrease in the sub-basin areas. (2) The SWA changes of all major natural lakes are relatively stable, and the only decreasing trend of SWA was observed in the Hongjiannao lake; the SWA of Xiaolangdi and Longyangxia reservoirs changed significantly with an increasing trend among the large reservoirs in the main river channel, and SWA increasing trends can be observed in the 50 sub-basins located in the middle and lower reaches. (3) Precipitation had the least effect on the increasing trend of SWA, and warming caused a decrease of SWA in the middle reaches, but led to an increase of SWA in the source area. The impacts of vegetation greening on the SWA trend in the main channel area and sub-basin areas are 10.12 km²/a and 7.26 km²/a, respectively. Residual factors had a negative reffect on the SWA trend in the sub-basin areas, where the SWA reduction induced by human water use was much greater than the SWA increment induced by small water conservancy projects. However, residual factors had a positive effect on the SWA increase due to the great regulating storage capacity of large reservoirs in the main river channel area.

The "Hu Line" is a geographical line connecting Heihe City and Tengchong City in China. It is densely populated on the southeast side of the "Hu Line" but sparsely populated on the northwest side. Since the implementation of New-type Urbanization strategy in 2014, the spatial pattern of population distribution on both sides of the "Hu Line" has changed a lot. We put forward the "Quasi-Hu Line" based on the boundaries of prefecture-level administrative divisions. According to the seventh population census data in 2020, this study focuses on the new characteristics of population spatial patterns and population growth patterns on both sides of the "Quasi Hu Line" from 2010 to 2020. We analyze the driving factors combined with the development of New-type Urbanization. The main conclusions are as follows: (1) The human-land relationship reflected by the "Hu Line" was still stable, and the overall distributions of densely populated and sparsely populated areas were also steady. In 2020, the population ratio of the southeast side to the northwest side was 93.5∶6.5. (2) The population share of the northwest side still increased slightly, but the increment was significantly lower than that before 2010. (3) The centralization index of the population on the northwest side turned from decline to increase after 2010, which indicated the concentration of spatial population distribution in the northwest half was similar to that in the southeast half. (4) The spatial differentiation of population growth on the southeast side has been strengthened. The negative population growth area accounted for 54.22% of the southeast side from 2010 to 2020, exceeding the positive population growth area. The population growth on the northwest side had also changed from the "relative balance" model to the "Matthew effect" model, with the negative population growth area accounting for 26.14% of the northwest side. (5) The relative population growth advantage of provincial capitals was becoming much more prominent. The spatial polarization process of population growth slowing down or negative growth was formed in the surrounding areas of provincial capitals. In addition, such a process on the northwest side was more significant than on the southeast side. (6) The driving factors, including the level of economic development, the scale of urban population size, and the level of administrative divisions, significantly impacted population growth. For the northwest side, the level of administrative divisions had a particularly significant impact on population growth, while the impact of urban agglomerations was not noticeable. In general, the northwest side had begun to present similar population spatial distribution patterns and driving factors with the southeast side. In the context of population migration and urbanization, the novel patterns of spatial population distribution reflected a kind of "breakthrough" of the "Hu Line". With China's total population turning to decline and urbanization entering the mid-late stages, more attention should be paid to the regional differences and coordination of demographical structures on both sides of the "Hu Line".

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.

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.

Understanding the conceptual connotation related to urban heat island (UHI) effect and clarifying its quantitative characterization methods are important foundations for effective UHI effect research. The global urbanization has made the UHI effect more and more common, which leads to a rapid increase in the number of related studies. In this context, different concepts related to UHI effect have emerged, and particularly, various quantitative characterization methods have been developed for surface urban heat island (SUHI) which has the advantage of spatial heterogeneity characterization. However, there is still a lack of systematic review of quantitative characterization methods of SUHI. Therefore, this study distinguished and analyzed the confusing concepts such as urban heat island, urban heat island effect, surface temperature and urban thermal environment. Then, the typical spatial locations and scale ranges of various UHIs were summarized. In the quantitative characterization of SUHI effect, this study categorized the SUHI range identification methods into four categories: methods based on urban and rural temperature threshold, temperature grade threshold, Gaussian fitting parameter, and temperature attenuation mutation. The current SUHI range identification research focuses on the cognition of the SUHI impact scale. This study also sorted out the SUHI intensity indicators corresponding to various range identification methods. Understanding the essential connotation of each indicator is the prerequisite for grasping the potential differences between the indicators. Future research should integrate multi-source SUHI monitoring methods, develop large-scale SUHI quantitative characterization methods, and cognize connected SUHI spatial morphology.