Table of Content

    25 November 2019, Volume 74 Issue 11 Previous Issue    Next Issue
    85th Anniversary of Acta Geographica Sinica
    The Geographical Society of China and the development of the Acta Geographica Sinica
    ZHANG Guoyou, HUANG Jian, ZHU Hong, HE Peidong
    2019, 74 (11):  2197-2208.  doi: 10.11821/dlxb201911001
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    The current Geographical Society of China (GSC) is the product of a merger of the Chinese Geographical Society established in 1909 and the former Geographical Society of China established in 1934. The establishment of the GSC and the launch of the journal Acta Geographica Sinica in 1934 are not only two major events in the history of Chinese geography, but also two spotlights in the history of Chinese education and science. This is the key point of the concept of science advocated by the New Culture Movement. The establishment of GSC clearly separated modern geography from traditional geoscientology and entered on the historical stage in the name of science. What's more, the publication of Acta Geographica Sinica enabled Chinese and foreign geographers to enjoy a high-end professional academic source in China. The emergence of the society and its journal was also a direct manifestation of wartime concepts such as "science saves the country" and "invigorating China through science."Under the organization and promotion of the GSC, the older generation of geographers worked hard and published a series of important articles in the Acta Geographica Sinica. The modern geographers who worked tirelessly finally drew the attention of the ruling class and occupied a place in the top-down design of the country. Although their understanding of the importance was mainly in the high-level and professional academic circles, it planted the seed for the later vigorous development of Chinese geographic science and laid a solid scientific foundation for awakening the ordinary people. In retrospect, the establishment of GSC and Acta Geographica Sinica was the beginning of Chinese geographic science and has become the promoter and witness of the development of Chinese geographic science. On the 110th anniversary of the founding of the GSC, we should inherit the spirit of the older generation of scientists, enrich the geographic science, provide better service for the construction of the country, and improve the scientific literacy of ordinary people.

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    Development of geographical research in China through the lens of publication in the Acta Geographica Sinica between 1934 and 2018
    HE Shujin, LIU Changming, YUAN Zhenjie
    2019, 74 (11):  2209-2229.  doi: 10.11821/dlxb201911002
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    This paper employs Citespace to process the publication data of the Acta Geographica Sinica between 1934 and 2018. It will examine and summarize the features of the historical development of geographical research in China. A total of 4129 articles published in the journal are analysed in four aspects, including key themes, trends of the themes, historical burst terms and changes of contributing institutions. Four stages of development are considered, which include establishment (1934-1949), transformation (1950-1966), development stage (1978-1995) and comprehensive development stage (1996-present). Findings of this paper are: (1) the historical development and transformation of the journal, which reflects the capability of self-innovation and significant vitality of the Geographical Society of China in the past, present and future; (2) physical geography, human geography, remote sensing and geographical information system, and ecological and environmental studies, which are four main research fields of the Geographical Society of China, with a transforming trend from physical geography, to human geography, and an interdisciplinary research on the human-earth system; (3) Four main research "turns" are identified: ① research perspectives: towards a comprehensive, interdisciplinary and integrated geographical study; ② research content: from the studies of physical elements to the studies of humanistic elements, and to the studies of processes, mechanism and influence within/of the human-earth system; ③ research paradigm: towards a critical and integrated approach involving scientific positivism, scientism and humanism; ④ research method: from on-site observation and digital modelling to an integrated analytical toolkit, based on multi-sources of spatial and temporal information. Future studies are expected to further extend and improve the system of geographical theories, enhancing critical thinking on the research paradigm and incorporating them with cognate subjects, and using an open mind to promote the influence of geographical research in the fields of both natural science and social science.

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    The inheritance and development of transportation geography in China: Based on analysis of papers published in Acta Geographica Sinica
    JIN Fengjun,CHEN Zhuo
    2019, 74 (11):  2230-2242.  doi: 10.11821/dlxb201911003
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    Understanding the development process and direction of China's transportation geography scientifically and accelerating the theoretical and technological innovation closely associated with the concrete practice are of great significance for the disciplinary development and holding on to the direction of practice. Based on the transportation geography papers published in Acta Geographica Sinica since its founding, this paper discussed the development process of China's transportation geography, and summarized the driving forces and development direction of the discipline. (1) Going through exploration stage, initial stage, formation stage and deepening stage, China's transportation geography has gradually identified the nature of the applied discipline synthesized by nature, humanity and technology, constituted a prominent comprehensive characteristic, and established a relatively complete discipline system on the basis of research content, transportation modes and spatial scales. (2) The demand of national and regional development is the essential driving force for the development of China's transportation geography, while data and method innovation, interdisciplinary demands and international theoretical introduction play a significant role in promoting development of the discipline. (3) The development of the discipline has three leading orientations: humanism, ecologicalism and technicalism. In the future, it is necessary to track diverse orientations in the long term and coordinate the discipline system and development direction timely so as to maintain the discipline superiority and competitiveness of China's transportation geography.

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    Geographical studies of Southwest China based on articles published in Acta Geographica Sinica from 1934 to 2018
    DU Fangjuan,ZHOU Yue,ZHUANG Shurong,YE Shian
    2019, 74 (11):  2243-2259.  doi: 10.11821/dlxb201911004
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    Regions continue to be one of the most logical and satisfactory ways of organizing the geographical information. Southwest China has always been concerned by geographers at home and abroad for its unique geographical phenomena. Its research vein could be looked into and given some useful suggestions for the future research through analyses of the articles published in Acta Geographica Sinica during 1934-2018. The results show that: (1) Articles about Southwest China covered almost all the subjects of geography, and the research results about geomorphology, meteorological climate, integrated physical geography, and ecological environment are the most widely published, while those on cities, ethnic groups, transportation and health are less concerned; (2) Up to 2018, the research had experienced four stages, early traditional regional research, task-led discipline, connecting the preceding and the following, and diversified development; (3) The periodical changes of the quantity and contents of these articles are influenced by the pattern of national affairs, and by the changes of the research paradigm of geography; (4) The articles published in Acta Geographica Sinica are of high research level, no matter from the academic perspective or the research methods, and many studies on regional nature, humanities, social economy and ecological environment are at the forefront of academic research, representing the academic research on geography of Southwest China; (5) However, the growth rate of articles about this region is far behind the increase in the number of articles in Acta Geographica Sinica, and the external research institutions and universities account for a large proportion of the number of articles, while the locals are weak. Compared with physical geography, there are fewer studies on human geography. As China's "island in the sky" and "cradle of ancient humans beings", Southwest China should be re-examined in the fields of the traditional and modern collision, boundary contact and conflict, and inter-regional contact and competition from the perspective of new regional geography, and continue to achieve the geographical significance of the study region.

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    Spatio-temporal Coupling of Water-land Elements in Mountainous Areas
    Agent based model of land system: Theory, application and modelling framework
    DAI Erfu, MA Liang, YANG Weishi, WANG Yahui, YIN Le, TONG Miao
    2019, 74 (11):  2260-2272.  doi: 10.11821/dlxb201911005
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    Land change science has become an interdisciplinary research direction for understanding human-natural coupling systems. As a process-oriented modelling approach, Agent based model (ABM) plays an important role in revealing the driving forces of land change and understanding the process of land change. This paper starts from three aspects: the theory, application and modeling framework of ABM. First, we summarize the theoretical basis of ABM and introduce some related concepts. Then we expound the application and development of ABM in both urban land systems and agricultural land systems, and further introduce the case study of an model on Grain to Green Program in the Hengduan Mountains region, Southwest China. On the basis of combing the ABM modeling protocol, we propose the land system ABM modeling framework and process from the perspective of agents. In terms of urban land use, ABM research initially focused on the study of urban expansion based on landscape, then expanded to issues like urban residential separation, planning and zoning, ecological functions, etc. In terms of agricultural land use, ABM application presents more diverse and individualized features. Research topics include farmers' behavior, farmers' decision-making, planting systems, agricultural policy. Compared to traditional models, ABM is more complex and difficult to generalize beyond specific context since it relies on local knowledge and data. However, due to its unique bottom-up model structure, ABM has an indispensable role in exploring the driving forces of land change as well as the impact of human behavior on the environment.

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    Spatio-temporal coupling characteristic of water-land elements and its cause in typical mountains
    ZHOU Peng, DENG Wei, PENG Li, ZHANG Shaoyao
    2019, 74 (11):  2273-2287.  doi: 10.11821/dlxb201911006
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    Water and land resources are the foundation for human wellbeing. The coupling of water-land elements in mountainous areas is closely related to the functionality of production-living-ecology space, whose coupling process and features are closely related to ecosystem services and sustainable socio-economic development in mountainous areas. Through constructing a more scientific coupling index of water-land elements (CIWL), the present study conducted a large-scale and long-term analysis of the coupling characteristics of the Taihang Mountains, Hengduan Mountains and Guizhou-Guangxi karst mountains. The influencing factors of the coupling index in each period were analyzed by employing geodetector method. The results show that: (1) The three mountainous areas are significantly different in spatial differences of coupling index of water-land elements. The Taihang Mountains are dominated by water deficiency, while the Hengduan Mountains are by the balanced area. The Guizhou-Guangxi mountainous areas are dominated by water deficiency and the abundant areas. (2) In terms of the vertical differentiation, the coupling of water-land elements of the three major mountainous areas varies at 1300 m, 1800-3400 m and 500-1500 m, respectively, with the coupling index of water-land elements in ecological functional sub-regions indicating that the forest ecological sub-region > forest grass ecological sub-region > agro-ecological sub-region. (3) Natural factors and human factors are responsible for spatial differentiation of coupling index, among which, the climate is a dominant driving factor, the topography and land use type are secondary, and the human factors are superimposed on the natural factors, jointly causing the complexity and variation of the coupling of water-land elements. The coupling index of water and land elements established in this paper has deepened the study of spatial-temporal processes of water and land interaction in mountainous areas, thereby providing a decision-making reference for coping with the sustainable development of mountainous areas in a changing environment.

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    Spatio-temporal variations of precipitation and runoff and analyses of water-heat-human-land matching characteristics in typical mountainous areas of China
    JIA Yangwen,HAO Chunfeng,NIU Cunwen,QIU Yaqin,DU Junkai,XU Fei,LIU Huan
    2019, 74 (11):  2288-2302.  doi: 10.11821/dlxb201911007
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    Mountainous areas in China face complex problems due to conflicts between natural eco-environmental protection and socio-economic development. Mountain water resources have evolved in the context of climate change and human activities, which further affects their coordination and matching with regional climate resources, land resources and socio-economy. Hence, it is of fundamental significance for mountain development to study these issues to identify key weakness and provide solutions. The paper focuses on three typical mountainous areas under different natural geographic conditions and at socio-economic development levels in China, namely, Taihang Mountains Area (TMA), Hengduan Mountains Region (HMR) and Guizhou-Guangxi Karst Area (GKA), and studies the spatio-temporal variations of precipitation and runoff from 1956 to 2015 by Mann-Kendall test based on national water resources assessment results and statistical data of land use and socio-economy. The characteristics of natural and socio-economic factors are analyzed by matching distance and imbalance index. In this process, four groups of parameters are selected, including water (precipitation and runoff), heat (accumulated temperature and radiation), land (total area and farmland area) and socio-economy (population and GDP). The results indicate that, the water resources endowment of TMA is the worst, and significant reduction of runoff since 2000 makes it even worse, while the precipitation and runoff of HMR and GKA are abundant and there is no obvious change trend. According to the analysis of regional water-heat-human-land matching characteristics, TMA mainly suffers from water shortage, land and heat resources have great disadvantages in most parts of HMR with uneven distribution of water and heat, and land resources are relatively deficient in all counties of GKA. In general, mismatching degree of water and other factors is the highest, and the allocation and coordination of water are the key issue for sustainable development of mountainous areas, especially in TMA.

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    Spatial pattern of debris-flow catchments and the rainfall amount of triggering debris flows in the Hengduan Mountains region
    HU Kaiheng, WEI Li, LIU Shuang, LI Xiuzhen
    2019, 74 (11):  2303-2313.  doi: 10.11821/dlxb201911008
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    Environmental factors determine the spatial and temporal distribution of debris flows. Understanding the relationship between debris flows and their effective factors is important for debris flows risk assessment at regional scale. In this paper, geographic detectors and gray correlation analysis are used to explore the relationship between 11 influencing factors, including precipitation, climate, landforms, geology, land cover type, soil thickness and topographic wetness, and the spatial distribution of debris flows-prone catchments, as well as the spatial and temporal correlation between precipitation and debris flows disasters in the Hengduan Mountains region. The results show that the topographic wetness index is the most dominant factor controlling the spatial distribution of the catchments, followed by topographic relief and soil thickness. Temporal correlation between debris flows disasters and precipitation characteristics has large regional heterogeneity. The rainfall characteristics of debris flows disaster events in different regions exhibit significant difference. The frequency of debris flows with rainfall, topographic wetness, topographic relief and soil thickness in the Hengduan Mountains region varies significantly in different zones, which indicates that not only the rainfall but also the other factors controlling the spatial pattern of debris flows should be reflected in debris flows early warning model in the region.

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    Climate Change and Ecological Environment
    Multi-model ensemble projection of crop yield of India under RCP 8.5 climate change scenario during the 21st century
    ZHANG Xuezhen, LI Xiaxiang, ZHANG Lijuan, XI Jianchao, DAI Erfu
    2019, 74 (11):  2314-2328.  doi: 10.11821/dlxb201911009
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    Using the multi-model ensemble projections of wheat and rice in India during the 21st century from the Inter-Sectoral Impact Model Intercomparison Project, this study assessed the future changes in crop yield under the RCP 8.5 emission scenario. The results show that the multi-model ensemble simulations generally reproduce the spatial variability in crop yield that is represented by ground measurements. Furthermore, the simulations reproduce the response of crop yield to climate changes, which is characterized by negative correlations between crop yield and temperature and positive correlations between crop yield and precipitation. Under the RCP8.5 emission scenario, temperature and precipitation during the growing season of wheat and rice will increase. Generally, temperature will increase at a higher rate than precipitation; the increases in temperature and precipitation during the wheat growing season will be stronger than that during the rice growing season. In terms of spatial dimension, the increase in temperature will be weakened gradually from the north to the south, while that of precipitation will be intensified gradually from the north to the south. Temperature increase in the wheat producing areas will be stronger than that in the wheat non-producing area, while precipitation increase in the wheat producing areas will be weaker than that in the wheat non-producing areas. However, the scenario is predicted to be reversed for the rice producing areas. In response to the climate changes, wheat and rice yields will decrease in the 21st century, particularly in the second half. The decrease in wheat yield will be greater than that of rice yield. In the first half of the 21st century, wheat and rice yields are predicted to decrease at the rates of 1.3%/10 a (P < 0.001) and 0.7%/10 a (P < 0.05), respectively. In the second half of the 21st century, they are predicted to decrease at the rates of 4.9%/10 a (P < 0.001) and 4.4%/10 a (P < 0.05), respectively. The drought stress resulting from climate warming might be the main reason for this projected yield reduction. The greatest decrease in wheat yield (as high as 60%) will occur in the southwest part of the Deccan Plateau, and the greatest decrease in rice yield (as high as 50%) will occur in the northern part of the Gangetic Plain. These findings suggest that food supply in India will face extreme challenges under the future climate change scenarios.

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    Numerical simulation and spatial distribution of summer precipitation in the Qinling Mountains
    XIN Rui, DUAN Keqin
    2019, 74 (11):  2329-2341.  doi: 10.11821/dlxb201911010
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    The Qinling Mountains serve as a dividing line for China's climate. The dearth of precipitation data in high-altitude areas limits the study of climate and water resource changes in this region. To determine the spatial distribution of precipitation, the weather research forecasting (WRF) model was used to simulate summer precipitation in the Qinling Mountains and surrounding areas in 2017 by employing three convective parameterization schemes (KF, BMJ and GF). Both the simulation results and satellite data reveal that precipitation is consistent with the terrain's topography, and there is a spatial pattern of strip distribution from south to north accompanied by a high precipitation zone in the Qinling Mountains. The mountains have an evident blocking effect on the northward transport of water vapour, resulting in precipitation on the southern slope of the Qinling Mountains being significantly greater than that on the northern slope. However, the analogue value is larger than the satellite precipitation data. The primary reason that more precipitation is observed in the KF scheme simulation is that the strong convective instability leads to an overestimation of convective precipitation. The GF scheme simulates grid-scale precipitation, which result in more large-scale precipitation due to atmospheric wetness. The simulated values of the BMJ scheme are closest to the observed values. Increasing the resolution to 2 km can significantly improve the simulation level of the model in the Qinling Mountains, and there is great potential for improving precipitation estimation at the highest elevations of the mountains by using a suitable cumulus parameterization scheme.

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    Impacts of urbanization on spatio-temporal variations of temperature over the Pearl River Delta
    WU Zixuan, ZHANG Qiang, SONG Changqing, ZHANG Fen, ZHU Xiudi, SUN Peng, FAN Keke, YU Huiqian, SHEN Zexi
    2019, 74 (11):  2342-2357.  doi: 10.11821/dlxb201911011
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    Daily temperature data at 21 stations across the Pearl River Delta during the period of 1967-2015 were selected, and these stations were divided into urban stations and suburban stations based on population, population density and DMSP/OLS data. Meanwhile, spatio-temporal variations due to urbanization were investigated by comparing the temperature changes at urban and suburban stations. The results show that: (1) In the past 50 years, the annual average temperature, the average maximum temperature and the average minimum temperature in the Pearl River Delta region increased significantly, and the average minimum temperature increased at the highest rate, or 1.05-1.16 times of the average temperature and 0.95-1.32 times of the average maximum temperature, respectively. Among them, the seasonal difference of annual average temperature change rate is generally manifested as the strongest temperature increase in autumn and winter, with the temperature increase rate higher than 0.3 ℃/10a, and the temperature increase rate is weaker in spring and summer, with the temperature increase rate as low as 0.16 ℃/10a. (2) Using urban and Sea Surface Temperature (SST) comparison to study the urbanization effect, affected by urbanization, the annual average temperature of the Pearl River Delta is increasing by 0.096 ℃/10a. (3) Using urban and rural comparison to study the urbanization effect, from 1967 to 2015, urbanization leads to the temperature increase in urban areas. Generally speaking, urbanization contributes the most to the increase of average minimum temperature. Meanwhile, the seasonal difference in the contribution rate of urbanization to the annual average temperature change indicates that the increase rate is stronger in summer and winter, with the contribution rate higher than 11.8%, and lower in spring and autumn, with the contribution rate being only 4.46%. (3) The selection of stations division method, the different periods of urbanization development and time scale of research all lead to the uncertainty of the research results on the warming effect of urbanization. Different stations classification methods indicate that urbanization contributes the most to the increase of the minimum temperature, and for a longer time scale, the contribution rate of urbanization to the increase of the minimum temperature is up to 38.6%.

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    A method to identify the drought-flood transition based on the meteorological drought index
    YANG Jiawei, CHEN Hua, HOU Yukun, ZHAO Ying, CHEN Qihui, XU Chongyu, CHEN Jie
    2019, 74 (11):  2358-2370.  doi: 10.11821/dlxb201911012
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    A new method was proposed to identify drought-flood transition events by combining a drought-flood index (Standard Weighted Average Precipitation, SWAP) with the multi-threshold theory. This method was tested in the Yangtze River Basin using daily precipitation data from 212 stations for the 1961-2017 period. With this method, the meteorological drought and rainstorm flood in the representative station were identified, and representative regional drought-flood transition events and spatiotemporal patterns of drought-flood transition were analyzed. The results show that: SWAP is an effective index to identify the meteorological drought and rainstorm flood. K-means clustering can classify similar drought-flood transition events into one cluster. The drought event plays a dominate role in drought-flood transition events for the middle and lower reaches of the Yangtze River Basin in 2011, and the drought lasts for a much longer duration than the flood during the drought-flood transition event. Drought-flood transition events show an obvious regional pattern for the Yangtze River Basin with low frequency for the upper reaches and high frequency for the middle and lower reaches. In addition, the drought-flood transition frequency presents an increasing trend recently for most parts of the Yangtze River Basin. Overall, the results imply that the proposed method combining meteorological drought index with multi-threshold theory is capable of identifying drought-flood transition events, and can be further used for predicting drought-flood transition events.

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    OSL dating of the pedo-stratigraphic sequence and the prehistoric flash floods and mudflows over the Lajia Ruins of Qinghai Province
    CUAN Yuda, HUANG Chunchang, PANG Jiangli, ZHOU Yali, ZHANG Yuzhu, GUO Yongqiang, WANG Haiyan, ZHAO Qiqi
    2019, 74 (11):  2371-2384.  doi: 10.11821/dlxb201911013
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    Environmental change and human-land relationship evolution over the Qinghai-Tibet Plateau are the frontiers of global change science. The Lajia Ruins in the Guanting Basin situated in the northeast margin of the Qinghai-Tibet Plateau has preserved many records of the Holocene environmental change, human activities, complex surface process evolution and abrupt catastrophic events. Therefore, the Lajia Ruins has received extensive attention from scientists from different fields, and has also attracted attention from world media. It is still quite controversial about the causation and age of the prehistoric catastrophe. After extensive field works over the years, a complete pedo-stratigraphy profile of soil and sediments has been found in the northern part of the Lajia Ruins. On the basis of field pedo-sedimentological observation and description, as well as physic-chemical analysis and OSL dating on the soil and sediment samples taken from the profile, a pedo-stratigraphic sequence and related chronology have been established in the Lajia Ruins. The results show that the profile has been developed from 12000 a BP. The pedo-stratigraphic sequence includes the Late Pleistocene Malan loess (L1-1), Holocene transitional loess (Lt), the Middle Holocene palaeosol (S0), the recent loess (L0) and the modern topsoil (MS). The Middle Holocene palaeosol (S0) is separated by three layers of red clay, which were deposited by large flash floods and mudflows during 3960-3650 a BP. These catastrophic events occurred at about 3850 a BP, 3800 a BP and 3600 a BP, respectively. The first mudflow event overflowed the gully channel and spread over a large area on the Yellow River terrace, and covered the eastern part of the large settlement of the Qijia Culture at 3850 a BP. All these facts indicate that the Lajia Ruins was destroyed by earthquakes in combination with large flash floods and mudflows coming along the gullies that originated from the hills of the Tertiary Red Formation. These results are very important in understanding environmental change and human-land relationship evolution, formation of the settlement of the Qijia Culture, pre-historical human impact and causation of catastrophe in the Guanting Basin.

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    Aeolian sediments and their paleoenvironmental implication in the Yarlung Zangbo catchment (southern Tibet, China) since MIS3
    LING Zhiyong, JIN Jianhui, WU Duo, LIU Xiangjun, XIA Dunsheng, CHEN Fahu
    2019, 74 (11):  2385-2400.  doi: 10.11821/dlxb201911014
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    The aeolian deposits in the Yarlung Zangbo catchment are widely developed, and its sedimentary development model is complex. The climatic implication and chronological boundary of the aeolian sediments are not clear enough. Therefore, from the perspective of the whole basin, this paper comprehensively analyzed the development mechanism and mode of the aeolian sediments in different regions. At the same time, the chronological data of aeolian deposition is normalized and compared with the classical curve of global climate. The results show that: (1) The aeolian deposits in the basin have prevailing wind field development patterns and local wind field development patterns, and different patterns of aeolian sediments have different indications for the environment. (2) The aeolian sediments in the basin are mostly deposited in the Last Glacial Maximum (LGM), which mainly developed in different periods since the Late Glacial Period (15 ka BP), and the rich source of alluvial debris may be the main controlling factor of the aeolian activities. The aeolian sediments forming in the earlier time were brought into the river and failed to be preserved due to the warming climate and the erosion transport caused by glacial ablation after the LGM. (3) Since the LGM, the aeolian deposition process of Yarlung Zangbo has been controlled by the regional and global paleoclimate environment, and the fluctuations are drastic. The aeolian sedimentary process of different climate stage have different records to the 30°N summer insolation, the Indian monsoon and westerly winds change signal, but have a better response to the Younger Dryas (YD), global cold event. In short, the sedimentary process of Yarlung Zangbo is similar with that of the other regions on the Tibetan Plateau, and both recorded the global paleoclimatic change, but have its regional uniqueness. 4) The strong accumulation process of aeolian sediments in the Yarlung Zangbo catchment is not a simple correspondence with the global classical climate curve, and it presents a more complex response pattern to global climate change, which shows that the aeolian deposition process of the alpine valley environment is not only affected by the climate of the large area, but also controlled by many local environmental factors. Their relation with the paleoclimatic environment is complex.

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    Study on adaptive governance of social-ecological system: Progress and prospect
    SONG Shuang, WANG Shuai, FU Bojie, CHEN Haibin, LIU Yanxu, ZHAO Wenwu
    2019, 74 (11):  2401-2410.  doi: 10.11821/dlxb201911015
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    Social-Ecological System (SES) is composed of social subsystem, ecological subsystem and the interaction between them; its structure, functions, and characteristics are different from those of social subsystem or ecological subsystem alone. Relying on adaptive social mechanisms of power-sharing and decision making, the adaptive governance of SES aims to guarantee human well-being in a sustainable manner under dynamic conditions. Adaptive governance theory is influenced by "common pool resources management", "resilience" and "governance", and lays a foundation for the construction of transformative governance and collaborative governance. This theory has three main objectives: (1) understanding and coping with the multi-stability, nonlinearity, uncertainty, integrity and complexity of SES; (2) establishing non-confrontational social structure, power-sharing structure and decision-making structure, and match with social subsystem and ecological subsystem; (3) achieving sustainable management of ecosystem services through an integrated approach. Therefore, in the face of the "Anthropocene" of human-behaviour-dominant surface processes, achieving adaptive governance helps to deal with the complexity and uncertainty of SES. Given the rapid changes in China's environment and the increasingly complicated interactions between China and countries all over the world, it will be helpful for future studies to pay close attention to the following fields: (1) understand the multi-interaction processes of a coupled system, and enhance its adaptability; (2) emphasize the significance of a holistic approach of studying SES; (3) improve the ability to understand and predict system dynamics in the context of environmental change.

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    Adjustment in the main-channel geometry of the lower Yellow River before and after the operation of the Xiaolangdi Reservoir from 1986 to 2015
    WANG Yanjun, WU Baosheng, SHEN Guanqing
    2019, 74 (11):  2411-2427.  doi: 10.11821/dlxb201911016
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    Previous studies indicate that the lower Yellow River experienced a continuous siltation period and a continuous scouring period during the past 30 years. However, the patterns of main-channel adjustments during these two periods are not clear. Based on measured discharge, sediment load, and cross-sectional data between 1986 and 2015, the changes in the morphological parameters (width, depth, and cross-sectional geomorphic coefficient) of the main channel were analyzed. The results showed that before the operation of the Xiaolangdi Reservoir (XLDR) from 1986-1999, the main channel shrunk continuously with decreasing width and depth. Because the decrease rate in width was greater than that in depth, the geomorphic coef?cient decreased in the reach above Gaocun. In contrast, for the reach below Gaocun, the decrease rate in width was smaller than that in depth, and the geomorphic coef?cient increased. After the XLDR began operating, the main channel eroded continuously, and the width and depth increased from 2000-2015. Because the increase rate in depth was obviously larger than that in width, the geomorphic coef?cient decreased in all sub-reaches. The cross-sectional geometry of the main channel exhibited different adjustment patterns during two periods. Before the XLDR operation, the main channel mainly narrowed in the transverse direction and silted in the vertical direction in the reach above Aishan (AS); in the reach below AS, the main channel primarily vertically silted. After the XLDR operation, the main channel adjusted by widening and deepening in the reach above AS; for the reach below AS, the main channel adjusted mainly by deepening. Compared to the decrease rates in main-channel width and depth during the siltation period, the increase rate in width during the scouring period was obviously smaller, while that in depth was larger. After continuous siltation and scouring, the main-channel cross-sectional geometry changed from relatively wide and shallow to relatively narrow and deep. The pattern of main-channel adjustment was closely related to the water and sediment conditions. For the braided reach, the geomorphic coef?cient was negatively correlated with discharge and positively correlated with suspended sediment concentration (SSC) during the siltation period. In contrast, the geomorphic coefficient was positively correlated with discharge and negatively correlated with SSC during the scouring period. For the transitional and wandering reach, the geomorphic coef?cient was negatively correlated with discharge and positively correlated with SSC.

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