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    Disciplinary structure of geographic science in China
    CHEN Fahu, LI Xin, WU Shaohong, FAN Jie, XIONG Juhua, ZHANG Guoyou
    Acta Geographica Sinica    2021, 76 (9): 2069-2073.   DOI: 10.11821/dlxb202109001
    Abstract3467)   HTML995)    PDF (727KB)(1555)      

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

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    China's changing population distribution and influencing factors: Insights from the 2020 census data
    LIU Tao, PENG Rongxi, ZHUO Yunxia, CAO Guangzhong
    Acta Geographica Sinica    2022, 77 (2): 381-394.   DOI: 10.11821/dlxb202202008
    Abstract2370)   HTML294)    PDF (2718KB)(520)      

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

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    Geomorphology and origin of yardangs in Lop Nur Lake region
    SONG Haoze, YANG Xiaoping, MU Guijin, QIN Xiaoguang, LIN Yongchong
    Acta Geographica Sinica    2021, 76 (9): 2187-2202.   DOI: 10.11821/dlxb202109011
    Abstract2225)   HTML282)    PDF (5648KB)(668)      

    Yardang is a typical, aeolian erosion landform widely distributed on Earth and discovered on other planets (Venus and Mars) too. Because of its various forms and volatility, yardang's morphological characteristics have attracted attention for generations. Lop Nur is located in the eastern part of the Tarim Basin in Xinjiang, China. Although there are many yardangs with various types in the area of Lop Nur, there is a lack of study about this impressive landform there. On the basis of field investigation, the authors found that UAV drones can efficiently and effectively collect yardang morphology data. Based on collected yardang morphology data (including field survey and DEM from UAV), using the terrain digital extraction method, after measuring the morphological parameter data of yardang, this article attempts to clarify the morphological characteristics of yardangs in the Lop Nur area, and to discuss its formation processes. The main conclusions are as follows: (1) The lengths of yardangs in the Lop Nur area are often < 20 m, although a few of them are even > 160 m. The widths of yardangs in our study area are mainly < 8 m, with a height of mostly < 2 m. It shows that the sizes of yardangs in the study area are generally small, although some large ones occur too. The ratio of length vs. width (R) of yardangs ranges from 2:1 to 4:1, and even > 10:1. The orientations of the yardangs in our study area are mainly toward 22.5°-67.5°, consistent with the predominant wind directions. Our observations suggest that the morphology of yardangs in the study area initiated from a dome-shaped form and then changed to drop-shaped, and finally to linear forms. The number of yardangs occurring nearby is often 3-4, and the distance between them is often < 20 m but occasionally 40-80 m. (2) The most likely evolution processes of yardangs in the Lop Nur area can be summarized into four stages: embryonic, juvenile, mature and decay periods. However, due to the influence of various controlling factors such as stratum sediment characteristics, wind erosion, and flowing water, yardang's morphology in the Lop Nur area become quite complex. (3) The developments of yardangs in the Lop Nur area have multiple periods. Since the Quaternary, there have been four main development periods in late Pleistocene (ca. 90 ka B.P.), early Holocene (8-9 ka B.P.), late Holocene (after 1.6 ka B.P.) and Little Ice Age (around 0.5 ka B.P.). According to morphological characteristics and environmental evolution, we infer that yardangs in Longcheng and Bailongdui were formed in the late Pleistocene, the northern Loulan grand yardangs formed in the Early Holocene, yardangs in central and northern Loulan formed in the late Pleistocene and the small yardangs in Loulan area formed probably during the Little Ice Age. Based on the chronology and yardangs' height, the average wind erosion rate near the Loulan site after 0.5 ka B.P. was calculated to be 6.2 mm a-1. Accurately describing the morphological characteristics of yardangs in the Lop Nur area and understanding its evolution procession is of great significance for analyzing the morphological development of yardangs and the regional wind erosion process.

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    Hu Huanyong's geostrategic thought and its monumental contributions
    DU Debin, CAO Wanpeng, XIA Qifan, YI Xinlei, MA Yahua
    Acta Geographica Sinica    2022, 77 (2): 261-274.   DOI: 10.11821/dlxb202202001
    Abstract2126)   HTML193)    PDF (1012KB)(501)      

    Hu Huanyong is one of the founders of modern Chinese human geography, a pioneer of geopolitical research and an outstanding thinker of geostrategy. This paper evaluates Hu Huanyong's geostrategic thought in the context of the changing international geopolitical environment in which China has embarked upon its path of national development. Hu Huanyong is believed to be the pioneer and visionary geographer who has long-term influence on China's geopolitical research and the formulation of China's geostrategy. He is credited for his systematic demonstration of the Chinese sovereignty over the islands in the South China Sea, namely the Nansha Qundao, Dongsha Qundao, Zhongsha Qundao, and Xisha Qundao, particularly his first naming of Nansha Qundao. He is ahead of his times with his comprehensive study of China's geopolitical environment, his prediction of the inevitable Japanese invasion into China and armed conflicts between Japan and the US, and his call for special attention to border governance and national security and defense. He has strongly advocated the recovery of the Ryukyu Islands, stressed the role that geographers play as the vanguards of China's territorial development, and called for a better integration of geography with national defense education. The paper concludes with an observation of the great significance to inherit and carry forward Hu Huanyong's geostrategic thought in the current global geopolitical environment characterized by unprecedented changes of the world in a century and the great rejuvenation of the Chinese nation.

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    Human geography research based on the new thinking of global rural-urban relationship
    LIU Yansui, LONG Hualou, LI Yurui
    Acta Geographica Sinica    2021, 76 (12): 2869-2884.   DOI: 10.11821/dlxb202112001
    Abstract2014)   HTML357)    PDF (2745KB)(980)      

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

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    Disciplinary structure and development strategy ofhuman geography in China
    FAN Jie, ZHAO Pengjun, ZHOU Shangyi, DENG Xiangzheng, WANG Chen
    Acta Geographica Sinica    2021, 76 (9): 2083-2093.   DOI: 10.11821/dlxb202109003
    Abstract1624)   HTML316)    PDF (1046KB)(778)      

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

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    Paradigm transformation in the study of man-land relations: From local thinking to global network thinking modes
    TAN Minghong, LI Xiubin
    Acta Geographica Sinica    2021, 76 (10): 2333-2342.   DOI: 10.11821/dlxb202110001
    Abstract1582)   HTML299)    PDF (1394KB)(537)      

    The early studies on the relationships between man and land in geography mostly focused on local regions and held the idea that "the land and water resources in a region feed the person in the region". In the traditional agricultural society, which relies heavily on natural resources, the idea, and regional geographic research and management practice under its guidance play a positive role in promoting the development between man and nature, and sustainable resource use. With the continuous increase in openness of man and land system resulted from development of science and technology and transport improvement, regional systems on different scales and at different economic development levels have formed an interdependent and coupled geographic network. Every region becomes a node in this network, and the formation and solution of regional problems are closely related to other nodes in the network, and are related to internal and external factors of the regional system. In some cases, external factors even play a more important role. The introduction of some concepts and methods marks the paradigm transformation of man-land relationship research from local thinking paradigm to global networked thinking paradigm, such as virtual water, ecological footprint, carbon emissions due to goods trade, resource link and tele-coupling of man-land relationship. This study discusses the paradigm transformation from three aspects: the evolution characteristics of man-land system, the changes of thinking paradigm and study methods in man-land relationships, and the realization paths and practical significances of the transformation of thinking paradigm in man-land relationship research. According to new ideas and thinking paradigms, traditional local thinking modes and related research themes such as regional carrying capacity can not fully express the new characteristics of man-land relationships. At present, studies related to regional carrying capacity have become an important issue in land use planning and urban planning in China. In the development of land use planning at different levels, "evaluation of resource and environmental carrying capacity" has become the premise and basis of planning. In the implementation of this concept, we usually simply uses population size as the control index. In the context of an increasingly open system, studies in the carrying capacity of resources and environment may be re-examined. This is especially necessary in smaller scale regional systems (e.g., at a county level).

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    Digital twin space and its applications: Concurrent discussion on the space reconstruction of geographical research
    LI Shuangcheng, ZHANG Wenbin, CHEN Liying, LIANG Ze, ZHANG Yajuan, WANG Zheng
    Acta Geographica Sinica    2022, 77 (3): 507-517.   DOI: 10.11821/dlxb202203001
    Abstract1447)   HTML236)    PDF (1476KB)(331)      

    The past two years have witnessed an explosive growth of digital twin research and its increasing application in a wide range of fields and scales. This urgently calls for a methodological framework to guide and consolidate the research and application of digital twin in various fields and with different structures and scales. In this paper, we first summarized and analyzed the development patterns of digital twin research in various fields, and then coined a term "digital twin space" (with definition and characteristics) as a framework to generalize and consolidate digital twins of various scales. Taking digital twin city as an example, we briefly elaborated the application of twin space. Space, as the carrier of the research object or the research object itself in geography, consists of natural geographical space, social space, and cyberspace. These three types of spaces, however, have not been fully integrated in different branches of geography. In order to boost comprehensive geography research, we propose to reconstruct geographical space research by integrating the three types of geographical spaces with the twin space. Digital twin space can interact with the physical space bilaterally in real time and thus break the barriers among the three types of geographical spaces from inside, which further helps realize the tasks of simulating realities, predicting changes, and regulating processes in integrated geography research.

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    Multi-dimensional proximity, trade barriers and the dynamic evolution of industrial linkages between China and the world market
    HE Canfei, YU Changda
    Acta Geographica Sinica    2022, 77 (2): 275-294.   DOI: 10.11821/dlxb202202002
    Abstract1367)   HTML186)    PDF (2658KB)(337)      

    As China enters the new normal era, the existing mode of joining into the global production network is confronted with the dual dilemma of internal dividend disappearance and external trade frictions. It is very important to explore the characteristics and driving forces of dynamic evolution of industrial linkages between China and other countries or regions in the world. Based on the world input-output table database from 1995 to 2014, this study depicts the global industrial interdependence network from the national scale using input—output analysis and social network analysis, and focuses on the evolution of China's role and position in this pattern using spatial econometric model. The main findings are as follows: China has become a bridge between East Asia and Southeast Asia and other emerging markets, thus upgrading from an "outsider" to an important hub in the industrial network linking Europe and the United States. However, from 2015 to 2019, the expansion of China's foreign industrial linkages has gradually reached a plateau. From the perspective of supply side, China's resource and manufacturing industries are constantly embedded in the supply side of the global production network. However, the overall external supply capacity of most China's service industry is relatively below global average. In terms of demand, China, as the "factory of the world" and a major country in infrastructure construction, has an increasing global influence in manufacturing and infrastructure. Nevertheless, the international influence of productive services like Transportation, Logistics and Finance has been declining since 2005. The Chinese industries obtain the local added value overall to continue to grow, but the efficiency of the added value capture is low. On this basis, this study explores the influence of multi-dimensional proximities and trade protectionism on China-global industrial linkages and their value added. Among them, the geographical and cognitive proximity has the most extensive influence, while the social and institutional proximities only promote and strengthen the intermediate production linkage with more complex forms of industrial linkages and final demand linkages. However, technical barriers and anti-dumping investigation have weakened China's foreign industrial links. The sanitary and phytosanitary measures have a significant weakening effect on the final demand linkage, but not on the intermediate product production. To sum up, the upgrading of production-oriented service industry and the efficiency of the acquisition of overall added value are the potential directions for the expansion of China's foreign industrial linkages, while the construction of domestic industrial cycle and industrial diversification are the reasonable measures for the expansion of China's foreign industrial linkages.

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    The rule cognition and theoretical construction of spatial pattern in China
    LU Yuqi
    Acta Geographica Sinica    2021, 76 (12): 2885-2897.   DOI: 10.11821/dlxb202112002
    Abstract1327)   HTML346)    PDF (1559KB)(752)      

    "Hu Huanyong Line", T-shaped development model, and dual-nuclei structure model can be roughly summarized as a "one-line, two-axis, and dual-nuclei" structure. They are all rule cognition and theoretical refinements on spatial pattern in China which were proposed by Chinese human geographers in different periods. "Hu Huanyong Line" is proposed based on the regular recognition of regional differences. This is the extension and expansion of geographical differentiation laws of physical geography in human geography, following the basic assumption of homogeneous regions. The discovery of the T-shaped model of Lu Dadao and the dual-nuclei structure of Lu Yuqi transcended the analytical thought of regional differentiation laws. They follow the basic assumptions of functional areas. Among them, the T-shaped model is the practical application of the point-axis system theory proposed by Lu Dadao in China. From the phenomenon perspective, the dual-nuclei structure is attached to the T-shaped development model, but subsequent research has completed the transformation from special to general. It has accomplished the whole process of scientific research in scientific discovery, mechanism analysis, mathematical derivation and practical application. Eventually, it becomes a regional spatial structure theory with strong broad applicability. From the theoretical level, "Hu Huanyong Line" based on the assumption of homogeneous region and T-shaped model based on the assumption of functional region belong to the analysis results of spatial differentiation law, but they can also be called theories. They are individual theories in geography, while the dual-nuclei structure theory belongs to a more general and applicable theory in the general scientific sense. Obviously, the trinity analysis of the "Hu Huanyong Line", the T-shaped model, and the dual-nuclei structure theory shows that, China is a country that is very suitable for regional analysis and geographical laws and theories refinement based on this. The research in this paper can provide research ideas and method references for the summary of regional spatial structure laws and theory refinement of human geography.

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    Analysis of the Bole-Taipei Line as the divide for regional coordinated development: Evidence from greenhouse gas emissions of Chinese cities
    FANG Kai, HE Jianjian, ZHANG Jiaqi
    Acta Geographica Sinica    2021, 76 (12): 3090-3102.   DOI: 10.11821/dlxb202112015
    Abstract1294)   HTML165)    PDF (5440KB)(333)      

    As the international political and economic situation has been undergoing profound changes, achieving regional coordinated development is essential for China to form a new development pattern dominated by the domestic economic cycle. The Bole-Taipei Line, which is perpendicular to the Hu Huanyong Line and is proposed by Professor Fang Chuanglin in February 2020, has the potential to be an appropriate representative of the coordinated and balanced line of China's regional development. By investigating the spatio-temporal distribution of greenhouse gas emissions among 338 Chinese cities from 2005 to 2015, and making use of the Theil index and the Gini coefficient that are appropriate for measuring the spatial equality on both sides of the Bole-Taipei Line and within the southwest and northeast parts, respectively, this paper attempts, for the first time, to underpin the scientific basis of the Bole-Taipei Line as China's regional coordinated development line. We find that: (1) Overall emissions of the carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorinated greenhouse gas show a balanced distribution on both sides of the Bole-Taipei Line, and there are small regional differences in sectoral CO2 emission intensity and per capita CO2 emissions. (2) There is a generally balanced distribution of greenhouse gas emission intensity and per capita emissions, as well as the sectoral CO2 emission intensity and per capita emissions within the southwest and northeast parts of the Bole-Taipei Line. The industrial and agricultural sectors serve as the major emitters of greenhouse gases and therefore require a low-carbon transition towards a more balanced distribution of greenhouse gas emissions on both sides of the Bole-Taipei Line. In conclusion, the greenhouse gas emissions as a measure of the magnitude of human activities on both sides of the Bole-Taipei Line are relatively balanced, which has justified the scientific robustness and rationality of the Bole-Taipei Line as a strategic line for socioeconomic development, and provided novel insights into China's regional coordinated development.

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    The dynamics of world economy geography and the role of China in economic globalization
    ZHU Shengjun, YANG Bofei, LIU Yi
    Acta Geographica Sinica    2022, 77 (2): 315-330.   DOI: 10.11821/dlxb202202004
    Abstract1265)   HTML199)    PDF (1667KB)(206)      

    From the perspective of economic geography, this paper studies the changing spatial pattern of world economy and China's role in different waves of economic globalization. Firstly, this study finds that the geographical pattern of world economy changes from "core-periphery" to "chain-reconfiguration", and to current "network-imbalance". Meanwhile the driving force of economic globalization shifts from "trade globalization" to "manufacturing globalization". At present, "multiple globalization" is involving into a new engine to driving the development of economic globalization. We then discuss that how China changes its role in economic globalization by changing modes of strategic coupling. We argue that the role transition of China breaks the traditional developing path which developed countries set for developing countries and theoretical spatial order put forward by classical industry gradient transfer, bringing new restructuring power and possibility for changing pattern of globalization. Finally, we discuss the impacts of COVID-19 pandemic on the development of economic globalization and the development trend of economic globalization in the post-pandemic era. Based on the analysis, we come up with some suggestions regarding to the potential development paths of China under the background of economic globalization.

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    Changes in global air temperature from 1981 to 2019
    SHEN Beibei, SONG Shuaifeng, ZHANG Lijuan, WANG Ziqing, REN Chong, LI Yongsheng
    Acta Geographica Sinica    2021, 76 (11): 2660-2672.   DOI: 10.11821/dlxb202111005
    Abstract1257)   HTML87)    PDF (3073KB)(413)      

    The determination of temperature changes in major countries since the 1980s is a key scientific method to reveal the spatial difference of global temperature change and to achieve a common global climate change. Based on seven sets of reanalysis data, this paper analyzed the spatio-temporal characteristics of global temperature change and the temperature change of major countries from 1981 to 2019 by using climate tendency rate and spatial interpolation. The results revealed that the global land air temperature in the stydy period varied at a rate of 0.320 °C/10a, exhibiting a significant increasing trend, with a cumulative increase of 0.835 °C. The mean annual land air temperature in the northern and southern hemispheres varied respectively at rates of 0.362 °C/10a and 0.147 °C/10a, displaying significant increasing trends, with cumulative increases of 0.828 °C and 0.874 °C,respectively. The global land surface air temperature displayed an increasing trend, with more than 80% of the land surfaces showing a significant temperature increase. Across the globe, the change rates of annual mean air temperature were higher at high latitudes than at middle and low latitudes, with the highest change rates in regions at latitudes of 80°N-90°N, followed by the second-highest rates in regions from 70°N-80°N, and the third-highest rates from 60°N-70°N. Greenland, Ukraine, and Russia had the highest increase rates of annual mean air temperature, especially Greenland, which experienced a temperature tendency rate of 0.654 °C/10a. The regions with the lowest increase rates of annual mean air temperature were mainly in New Zealand and areas on or near the equator including South America, Southeast Asia and Southern Africa, where the temperature tendency rates were < 0.15 °C/10a. Among the 146 countries surveyed in this paper, 136 countries (93%) showed a significant warming trend, 10 (6.849%) had no significant change in temperature, and only 3 countries showed a downward trend. Among them, since the 1980s, there are 4, 34, and 68 countries with global warming above 2.0 ℃, 1.5 ℃, and 1.0 ℃, respectively, accounting for 2.740%, 23.288% and 46.575% of the countries concerned in this study. This paper held that there had been no global warming hiatus since 1998.

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    Remotely sensed mapping and analysis of spatio-temporal patterns of land use change across China in 2015-2020
    KUANG Wenhui, ZHANG Shuwen, DU Guoming, YAN Changzhen, WU Shixin, LI Rendong, LU Dengsheng, PAN Tao, NING Jing, GUO Changqing, DONG Jinwei, BAO Yuhai, CHI Wenfeng, DOU Yinyin, HOU Yali, YIN Zherui, CHANG Liping, YANG Jiuchun, XIE Jiali, QIU Juan, ZHANG Hansong, ZHANG Yubo, YANG Shiqi, SA Rigai, LIU Jiyuan
    Acta Geographica Sinica    2022, 77 (5): 1056-1071.   DOI: 10.11821/dlxb202205002
    Abstract1214)   HTML26)    PDF (5124KB)(137)      

    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 "13th Five-Year Plan" period (2016-2020) and ecological civilization construction, as well as the impact of climate change.

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    The structure and characteristics of resident food consumption in rural areas of the Tibetan Plateau: Taking Three-Rivers Region in Tibet as an example
    WANG Ling'en, GUO Jiaxin, FENG Ling, LUO Yanhua, ZHANG Xianzhou, FAN Yuzhi, CHENG Shengkui
    Acta Geographica Sinica    2021, 76 (9): 2104-2117.   DOI: 10.11821/dlxb202109005
    Abstract1202)   HTML196)    PDF (1715KB)(422)      

    Resident food consumption is affected by factors such as the natural geographic environment and urbanization. At the same time, food consumption will affect regional food security and the development of agriculture and animal husbandry through market mechanisms. Taking the Yarlung Zangbo River and its two tributaries of Tibet (also known as Three-Rivers Region) as a typical case, this paper obtained the food consumption data of 262 rural residents by field surveys based on stratified sampling, and then analyzed the food consumption structure of the rural residents and its influencing factors in the Tibetan Plateau. The results indicated that: (1) The consumption of plant foods of the residents in the sample is 3.19 times that of animal foods, with vegetable and grain as the main plant food and meat and milk as the main animal food. And highland barley and highland barley liquor are important in the diet of Tibetans. (2) The scale and structure of food consumption of residents are closely related to the index of food self-sufficiency, and the characteristics of self-sufficient food consumption are significant. (3) Among different regions, family sizes, scales of migrant worker, income levels and family ages, the food consumption structure of residents varies, and the differences in the consumption of flour and fruits between different families are the most significant. (4) Regional differences, family sizes and migrant worker scales are the main factors that affect the comprehensive difference of food consumption in the sample rural areas. The research results of the paper can provide scientific basis and guidance suggestions for the improvement of food consumption structure, promotion of dietary nutrition and transformation and development of agriculture and animal husbandry in the Tibetan Plateau.

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    Drought impacts on crop yield: Progress, challenges and prospect
    LIU Xianfeng, FU Bojie
    Acta Geographica Sinica    2021, 76 (11): 2632-2646.   DOI: 10.11821/dlxb202111003
    Abstract1163)   HTML289)    PDF (1758KB)(595)      

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

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    Disciplinary structure and development strategy ofphysical geography in China
    CHEN Fahu, WU Shaohong, LIU Hongyan, YANG Xiaoyan, LIU Jianbao
    Acta Geographica Sinica    2021, 76 (9): 2074-2082.   DOI: 10.11821/dlxb202109002
    Abstract1157)   HTML246)    PDF (923KB)(673)      

    Physical geography, one of the branches of geographic science, is the basic discipline of geographic science. And it is the scientific foundation of ecology, environmental science and other related disciplines. Physical geography focuses on spatial characteristics, evolution and regional differentiation of the earth's surface. In the new period of rapid development of social economy, and science and technology, physical geography is more closely and widely connected with human geography and, information geography. Based on "The Development Strategy of Discipline and the Frontier Research (2021-2035)" and geography subject planning, this paper analyzed the forming process of the physical geography, expressed sub-discipline structure of comprehensive physical geography, sectoral physical geography, human survival environment, and proposed the development strategy of physical geography and its branch disciplines, key priority of development goals and directions.

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    Theoretical analysis on the mechanism and evolution law of urban-rural integration development
    FANG Chuanglin
    Acta Geographica Sinica    2022, 77 (4): 759-776.   DOI: 10.11821/dlxb202204001
    Abstract1143)   HTML97)    PDF (3366KB)(244)      

    Urban and rural areas are always an inseparable organic integration, and the high-quality new urbanization is the process of urban-rural integration and rural revitalization. "urban disease" and "rural disease" are connected with each other, and are the causes of each other, which are known as "urban and rural diseases". The radical cure of "urban disease" and "rural disease" requires rural revitalization and new urbanization. Based on the review of the research on urban-rural integration development at home and abroad, this study analyzes the pathological roots and opposition pattern of urban and rural areas from the theoretical level, explores the main controlling factors, driving mechanism, sustainability and four-stage regularity of urban-rural integration development, constructs the measurement test system of urban-rural integration development, and puts forward the triangular model of urban-rural multi-integration development. It is known that the urban-rural integration development in China is in the high integration stage of more towns and less villages in the late urbanization, and will enter the deep integration stage of more towns and less villages, namely the final stage of urbanization. This study explores the policy evolution path of urban-rural integration development in China since the founding of the People's Republic of China in 1949. China has generally experienced the policy evolution process from urban-rural coordinated development to the integration of urban-rural development and then to urban-rural integration development, and played an important guiding role in promoting new urbanization and rural revitalization. From the path level, it is suggested that the Central Urban and Rural Work Conference should be jointly convened, the National Urban-Rural Integration Development Plan should be jointly compiled, and the strategy of deep integration of urban-rural development should be implemented. The new urbanization and rural revitalization should be used as two different means to solve urban and rural diseases and improve the quality of urban and rural development. The theory and method of urban-rural integration development should be innovated, and the evaluation system should be constructed to quantitatively evaluate the depth of urban-rural integration development and build beautiful cities and beautiful villages. We should promote the development of new urbanization and rural revitalization in the direction of high synchronization, deep integration and co-prosperity, as well as improve the quality of urban and rural development and realize urban and rural modernization in a comprehensive way.

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    Analyzing spatial characteristics of urban resource and environment carrying capacity based on Covert-Resilient-Overt:A case study of Wuhan city
    WU Hao, JIANG Zhimeng, LIN Anqi, ZHU Wenchao, WANG Wei
    Acta Geographica Sinica    2021, 76 (10): 2439-2458.   DOI: 10.11821/dlxb202110008
    Abstract1092)   HTML204)    PDF (4837KB)(384)      

    The resources and environment carrying capacity (RECC) is a barometer of the development of urban territory space, so exploring the spatial characteristics of RECC is greatly significant for optimizing the territory spatial pattern. In this context, this paper uses new urban geographic information data, such as night-time lights and atmospheric remote sensing, points of interest, historical traffic situation and social media, on the basis of relevant procedures and guidelines. Furthermore, a theoretical framework based on the covert-resilient-overt analysis of the spatial characteristics of urban RECC is proposed, and a method combining spatial autocorrelation and fractal geometry is developed for spatial characteristics mining of RECC. Taking Wuhan as an example to carry out research, the results show that: (1) The distribution of RECC in Wuhan has significant spatial heterogeneity. Areas with higher covert carrying capacity are concentrated in the Huangpi District and Xinzhou District with superior ecological environment in the northern periphery of the city, areas with high resilient carrying capacity are concentrated in the central urban area with strong comprehensive risk response capabilities, and areas with high overt carrying capacity are located in the sub-center of the city with sound basic functions. (2) The RECC in Wuhan has positive spatial aggregation, and it shows significant radius-centripetal fractal and circle characteristics. The areas of high covert carrying capacity spread radially around, and the areas with high resilient carrying capacity are concentrated in the core of the city in a centripetal shape, the areas with high overt carrying capacity are between the areas with high values of covert and resilient carrying capacity. In conclusion, the spatial characteristics analysis and mining method system of urban RECC constructed in this paper make up for the shortcomings of the low dynamics of traditional data by introducing multi-source spatial temporal data, and improves the theoretical and technical paradigm of urban RECC research. The research provides a new way of thinking for the carrying capacity of urban resources and environment.

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    Building natural resources surveying and monitoring technological system: Direction and research agenda
    CHEN Jun, WU Hao, ZHANG Jixian, WANG Donghua, LIAO Anping, LIU Wanzeng, ZHANG Jun, MIAO Qianjun, FENG Wenli, LU Weihua
    Acta Geographica Sinica    2022, 77 (5): 1041-1055.   DOI: 10.11821/dlxb202205001
    Abstract1089)   HTML21)    PDF (2668KB)(103)      

    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.

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    Supraglacial debris-cover change and its spatial heterogeneity in the Mount Gongga, 1990-2019
    LIAO Haijun, LIU Qiao, ZHONG Yan, LU Xuyang
    Acta Geographica Sinica    2021, 76 (11): 2647-2659.   DOI: 10.11821/dlxb202111004
    Abstract1075)   HTML164)    PDF (4683KB)(570)      

    Debris-covered glaciers are widely distributed in western China. Supraglacial debris lying at the atmosphere-glacier interface plays an important role in the air-ice energy flux and thus influences the underneath ice melt rate. Varying glacier debris thickness will have influence on the mass balance gradient of the debris-covered glacier, the development of ice cliff, ponds and drainage systems, as well as on the downstream runoff process. Using Landsat TM/TIRS images between 1990 and 2019, this study extracted the debris coverage and estimated the thickness changes of the debris-covered glaciers in the Mount Gongga by using a physically-based thermal conductivity method. We found that: (1) The debris coverage of glaciers in the study area totally expanded by 43.824 km2, among which the Hailuogou Glacier expanded 2.606 km2, Mozigou Glacier 1.959 km2, Yanzigou Glacier 1.243 km2, Dagongba Glacier 0.896 km2, Xiaogongba Glacier 0.509 km2 and Nanmenguangou Glacier 2.264 km2. Annual expansion rates of their debris covered area are 3.2%, 11.1%, 1.5%, 0.9%, 1.0% and 6.5%, respectively. (2) In addition to debris cover area expansion, we found thickening debris layers, with glacier wide average debris thickness increasing by 5.2 cm, 3.1 cm, 3.7 cm, 6.8 cm, 7.3 cm and 13.1 cm for the above six mentioned glaciers, respectively. (3) Compared with glaciers on the east slope, debris-covered glaciers on the west slope of the Mount Gongga generally have higher debris cover rate but experienced lower debris cover expansion and lower terminal retreat rate during the past decades.

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    Disciplinary structure and development strategy ofinformation geography in China
    LI Xin, YUAN Linwang, PEI Tao, HUANG Xin, LIU Guang, ZHENG Donghai
    Acta Geographica Sinica    2021, 76 (9): 2094-2103.   DOI: 10.11821/dlxb202109004
    Abstract1015)   HTML177)    PDF (1925KB)(552)      

    The arrival of the information era has exceptionally advanced the development of geographic science. The research scope of the discipline has expanded from the space of traditional physical and human geography to the space of information geography. Meanwhile, the discipline gradually formed three subdisciplines, i.e., geographic remote sensing science, geographic information science, and geographic data science. In the context of preparing the disciplinary structure of geographic science of the "Development Strategy of Discipline and Frontier Research in China (2021-2035)", this paper summarized the history, definition, and disciplinary structure of information geography. Additionally, it highlighted the strategic layout of the discipline, as well as the goals and key directions of its priority development fields. We expect this paper to provide insight into the new discipline that could help promote the developments and applications of remote sensing and geographic information within the framework of geographic science, strengthening the synthesis of geographic research and promoting the integrated development of geographic science.

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    Special regionalization of cryosphere culture service in China
    WANG Shijin, XU Xinwu, DOU Wenkang, QIN Dahe
    Acta Geographica Sinica    2022, 77 (1): 16-34.   DOI: 10.11821/dlxb202201002
    Abstract1013)   HTML200)    PDF (6610KB)(576)      

    Drawing on the theories and methods of China's cryosphere service regionalization, physical and human geography regionalization, this paper integrates the components of China's cryosphere (glaciers, frozen soil and snow cover) and its social and cultural elements (nationalities, history, settlements, tourism culture and administrative divisions) and puts forward a special regionalization scheme of Chinese cryosphere culture service oriented by "cultural service+cultural industry+economic development" by using the methods of similarity and difference, comprehensiveness and dominance, hierarchy and logic, spatial continuity and administrative boundary. Based on spatial clustering method and the expert judgment, Chinese cryosphere culture divisions can be identified into five regions, namely, Qinghai-Tibet Plateau glacier-frozen soil- snow cover-culture region, northwestern China glacier - snow cover culture region, northeastern China frozen soil- snow cover culture region, northern China snow cover culture region and southern China snow cover culture region. According to the heterogeneity of culture and region, the five regions can be divided into 12 subcategories and 51 basic types. The thematic regionalization scheme is in good agreement with the spatial distribution of the cryosphere and the comprehensive regionalization of physical geography and human geography, which reflects the interdependent relationship between natural elements of the cryosphere and cultural elements of the cryosphere region and the rules of regional spatial heterogeneity. This research can deepen the understanding of China's cryospheric cultural service and their spatial heterogeneity, and provides a scientific basis for the protection, inheritance and promotion of cryospheric culture, as well as the development of cryospheric tourism industry, and the operation and management of related industries in different regions.

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    The spatiotemporal pattern evolution and influencing factors of CO 2 emissions at the county level of China
    WANG Shaojian, XIE Zihan, WANG Zehong
    Acta Geographica Sinica    2021, 76 (12): 3103-3118.   DOI: 10.11821/dlxb202112016
    Abstract998)   HTML177)    PDF (4458KB)(672)      

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

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    Views on the study of low-altitude airspace resources for UAV applications
    LIAO Xiaohan, HUANG Yaohuan, XU Chenchen
    Acta Geographica Sinica    2021, 76 (11): 2607-2620.   DOI: 10.11821/dlxb202111001
    Abstract934)   HTML139)    PDF (1904KB)(416)      

    With the development of hardware techniques and the decrease in equipment costs, unmanned aerial vehicle (UAV) has been widely applied in various socio-economic fields. However, there have been relatively few studies on low-altitude airspace resources as the operational carrier of UAVs. In this study, from the perspective of geography, the key issues related to the research of low-altitude airspace resources for UAV applications are discussed. Firstly, it is theoretically defined that low-altitude airspace is an important kind of natural resources with natural, social, and economic attributes, which should be included in the national natural resource development and utilization system; Secondly, we review the latest UAV applications based on the low-altitude airspace resources, categorize their constraints to utilize resources from natural and social aspects, and point out that the intervention of geography will speed up the development and utilization process of low-altitude airspace resources. Finally, this paper constructs the low-altitude airspace resource measurement index composed of three categories and nine sub-categories, and proposes four basic principles of low-altitude airspace resource measurement of "non-conflict utilization of resources, safety guarantee, benefit priority, and fairness", and thus forming a theoretical model of low-altitude airspace resource measurement with the three basic elements of national scope (S), true height (H) and time (t). This paper explores and discusses the low-altitude airspace resources from the perspective of geography, which will promote the interdisciplinarity of geography and aviation to some extent and the sustainable utilization of low-altitude airspace resources.

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    Spatial variation of migrant population's housing quality and its determinants in China's prefecture-level cities
    WANG Yufan, CHAI Kangni, ZHUO Yunxia, FENG Changchun
    Acta Geographica Sinica    2021, 76 (12): 2944-2963.   DOI: 10.11821/dlxb202112006
    Abstract887)   HTML128)    PDF (3765KB)(629)      

    Based on data from the 1% National Population Sample Survey 2015 and the 2014 China Migrant Population Dynamic Survey (CMDS), the paper selects four indicators to measure housing quality of the migrant population including floor area, housing facilities, construction period and living communities (urban or rural) and discusses the phenomenon about spatial differentiation of migrant populations' housing quality in 310 prefecture- and provincial-level cities in China, using GIS spatial analysis methods such as Moran's I coefficient and Getis-Ord Gi*. Besides, we investigate the influencing factors of migrant populations' housing quality. Some conclusions can be drawn as follows: (1) Compared with the local residents, the housing quality of the migrants is not that worse. (2) The spatial distribution of housing quality of migrant population presents marked spatial differentiation on cities of different levels and scales, population sizes and geographical divisions. (3) The results of spatial autocorrelation analysis demonstrate that there is a significant positive spatial correlation in the indicators of the migrant population's housing quality on a national scale, and identify the phenomenon of their spatial clustering and the centers of such spatial clustering. (4) The housing quality is influenced by both internal factors of migrant population and external factors of in-flow cities. (5) Population, economic development and the housing market play different roles in the housing quality of migrant population.

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    A discussion on some issues of hydro-geographical research
    LIU Changming, LIU Xuan, YANG Yafeng, WANG Hongrui
    Acta Geographica Sinica    2022, 77 (1): 3-15.   DOI: 10.11821/dlxb202201001
    Abstract886)   HTML120)    PDF (1512KB)(548)      

    Water-related issues have long been one of the most important topics in China, and these issues are related to a series of major national requirements, including social stability, people's livelihood and welfare, and economic development. Hydro-geography is an interdisciplinary subject of hydrology and geography that adopts the principles, perspective and methodologies of geography. The theory of the terrestrial surface system has an important enlightening effect on the systematic research of hydro-geography. First, this study discusses the cross-relationship and research content in hydro-geography, as well as the rise of research on global water systems and the ecohydrology. After summarizing the main advocates of terrestrial surface system theory and their viewpoints, this study explores the relationship between the comprehensive and regional aspects of geographic research, while proposing that the "three characteristics" (i.e., comprehensive, regional and orderly characteristics of processes) should be the research thought for hydro-geographical system. Furthermore, based on the expansion of the basic theories of the subject, this study presents several cases of systems science and technology that can deepen the spatiotemporal dynamic process mechanism (orderliness) of hydro-geography. Finally, several key development and research directions of hydro-geographic research in China are discussed, mainly including: research on the impact of climate change and impacts of human activities on the water cycle process; research on the dynamic evolution mechanism of the four major balances in ecohydrology; research on renewability of water resources; the process of evapotranspiration of plants (crops) and water-saving control; hydro-geographic zoning, mapping technology and intelligence technology applications.

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    A preliminary study of the strata and age of ancient agricultural terraces in the Ganjia Basin, northeastern Tibetan Plateau
    ZHANG Chenbin, WU Duo, CHEN Xuemei, YUAN Zijie, CHEN Fahu
    Acta Geographica Sinica    2022, 77 (1): 66-78.   DOI: 10.11821/dlxb202201005
    Abstract867)   HTML42)    PDF (3276KB)(337)      

    Agricultural terraces are a manifestation of man's ability to transform nature during the past thousands of years, and they have played an important role in the development of human society. The Ganjia Basin in Xiahe County, Gansu Province, is located in the northeastern Tibetan Plateau. A large area of banded landscape is distributed on the hills and piedmonts in the Ganjia Basin, which is claimed to be composed of large-scale abandoned ancient terraces. Based on fieldwork, satellite remote sensing data and GIS analysis in the present study, we found that the ancient terraces cover an area of 42.2 km2 and are mainly distributed on slopes between 2936 and 3326 m a.m.s.l. (meters above mean sea level) on both sides of the Yangqu River and its tributaries in the basin. Additionally, we analyzed various environmental proxies, including magnetic susceptibility (MS), grain size, the contents of total organic carbon (nitrogen) (TOC, TN), and palynological assemblages, from three representative sections of ancient agricultural terraces (GJAT-1, GJAT-1, and GJAT-3), and compared them with the MS values and clay content of a natural profile with accurate chronological control in the Ganjia Basin. The results indicate that the terraces are reclaimed paleosols dating to the Late Holocene (3000 kyr BP), and that the homogeneous MS values of the top 25-35 cm of the terrace profiles differ from those of the natural soil section, which confirms the existence of a cultivation layer in the terraces. However, the increases in the contents of TOC and TN above the cultivated layer, and the fact that the trend of MS in the terrace profile is broadly in line with the natural profile, indicate that the terraces were only used for a short interval and have been abandoned for a relatively long time. Combined with historical documentary evidence, we infer that the ancient Xiahe agricultural terraces were constructed as a result of the "Gongjianshou (bowman) militia farming" policy during the Northern Song China (1074-1125 CE). Climate reconstructions for the Northern Hemisphere and northern China demonstrate that the temperature was higher and that the precipitation increased during this interval, providing a favorable environment for agricultural production. Overall, our results provide a typical example of societal adaptation to climate change in the past.

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    Spatiotemporal differentiation and development process of tidal creek network morphological characteristics in Yellow River Delta
    MOU Kuinan, GONG Zhaoning, QIU Huachang
    Acta Geographica Sinica    2021, 76 (9): 2312-2328.   DOI: 10.11821/dlxb202109019
    Abstract819)   HTML83)    PDF (6899KB)(446)      

    The tidal creek is the main channel for the interaction of the land-sea ecosystem and has a high degree of spatiotemporal dynamics. Taking the old and new river courses in the Yellow River Delta as the boundary, the North Bank of the Yellow River (Area I), the East of the South Bank (Area II), and the West of the South Bank (Area III) are divided into comparative study areas. Remote-sensing images of five key time nodes from 1998 to 2018 are selected as the data source. Using the GIS spatial analysis function, the typical morphological characteristics of the tidal creek development degree are quantitatively characterized. The influence of factors such as the Yellow River diversion, wetland restoration project, and alien species invasion on the development process of tidal creeks is analyzed. Mining the temporal and spatial evolution of the tidal creek network through morphological parameters. Results are shown as follows. (1) The morphological characteristics of tidal creeks have obvious spatiotemporal heterogeneity. From the early stage of the Yellow River diversion in 1998 to the early stage of wetland restoration in 2004, the number of tidal creeks at all levels in Area I decreased significantly. Owing to the siltation of tidal flats and the effect of Spartina alterniflora, the number, density, and bifurcation ratio of tidal creeks in Area II showed an increasing trend. During the rapid expansion period of Spartina alterniflora in 2013, the curvature and bifurcation ratio of the tidal creek increased significantly. The level, length, and density of tidal creek development in Area III were the highest, as is the frequency of conversion between levels. The wetland restoration project has resulted in a significant reduction in the number and length of low-grade tidal creeks. Strong ocean dynamics inhibited the development of meanders in tidal creeks. (2) The diversion of the Yellow River and construction of side-curved spur dams have led to an increase in the overmarsh path length (OPL). This reduces the drainage density of the tidal creek network The rapid expansion of Spartina alterniflora increased the drainage density and the OPL continued to decrease. The degree of tidal creek development is Area III>Area II>Area I. (3) The tidal creek system changed rapidly from adolescence to middle age, and the development tended to be in dynamic equilibrium. The research results aid an understanding of the development process and evolution mechanism of large-scale tidal creeks, and provide scientific decision support for the development and utilization of coastal tidal flats.

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    Spatio-temporal change of global land cover and China's contribution
    LI Guangdong
    Acta Geographica Sinica    2022, 77 (2): 353-368.   DOI: 10.11821/dlxb202202006
    Abstract811)   HTML56)    PDF (7944KB)(386)      

    In recent decades, the global land cover has undergone drastic changes, and the impact of human activities on land cover change has become one of the most significant features of the "Anthropocene". The core tasks of coping with global "unprecedented changes in a hundred years" for China in the field of sustainable development is to scientifically assess the spatio-temporal process and new trends of global land cover change, analyze China's role and status in it, and propose optimal paths. We used geospatial analysis method and multi-source land cover data to explore the spatio-temporal process of global land cover change, analyze the transformation relationship between land types and the change trend of global "greening" and forest cover, and reveal the new characteristics and trends of land cover change in China. The results showed that the global land cover experienced significant changes from 1992 to 2015, and several hot spots formed, including central South America, sub-Saharan Africa, Central Asia, Southeast Asia and East Asia. China's forest coverage rate increased from 12.98% in 1990 to 23.34% in 2020, and the wetland area increased by 1908 km2, which contributed to the maintenance of global ecological security. The interactive conversion between cultivated land and forest is the most important land cover conversion relationship in the world. In terms of cultivated land occupied by urban land, China ranks first in the world, with an area of 73000 km2. The global leaf area index presented a global trend of significant increase from 1999 to 2019. With only 6.6% of the world's vegetation area, China contributed about 20% of the global increase in leaf area index and dominated the global "greening" process. The change of global forest coverage presents remarkably spatial agglomeration. China's forest area increased by 62.8376 million hectares (1990-2020), leading the world in forest restoration. The southwest China forest region and the Qinling-Daba mountains are the main areas of forest growth, and the Yangtze River Delta, the Guangdong-Hong Kong-Macao Greater Bay Area and parts of eastern Inner Mongolia are the main areas of deforestation. In the future, China should further enhance the balance and coordination between socioeconomic development and ecological protection, continue to promote the building of a beautiful China, and contribute more strengths and experiences to global ecological security and sustainable development.

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