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    10 November 2022, Volume 42 Issue 11 Previous Issue   
    Spatio-temporal Evolution and Driving Factors of Chinese Dry Port Logistics Hubs
    Jiang Ziran, Lei Liping, Jin Huanhuan, Zhang Jianzhen
    2022, 42 (11):  1857-1866.  doi: 10.13249/j.cnki.sgs.2022.11.001
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    This article analyzes the development mechanism of dry port logistics hub from multiple dimensions, measures the comprehensive development strength of China’s dry port logistics hubs by using the panel data from 2001 to 2018, reveals the spatial pattern and evolution characteristics of the hubs by using the methods of spatial analysis and Gini coefficient, and explores the main driving factors for the development of China's dry port logistics hubs. The results show that: 1) The development of hubs in the southeast is generally more mature and stable than that in the western, and shows the differentiation characteristics on the side of the Hu Huanyong Line; 2) The spatial differences in the development of dry port logistics hubs are more obvious, and the degree of difference is increasing; 3) Infrastructure and logistics operations have a greater contribution to the hub's Gini coefficient, but the impact of information technology has improved more significantly; 4) Population size, financial development and external environmental factors promote the development of hubs. Economic strength, education level and government investment have different impacts on hubs at different levels. The article is expected to provide scientific basis for the country to construct logistics system and optimize the logistics network giving full play to the supporting role of the logistics hub in the regional economy.

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    Network Spatial Connection of Coastal Port City System from the Perspective of Multiple Flows
    Qin Yafeng, Guo Jianke
    2022, 42 (11):  1867-1878.  doi: 10.13249/j.cnki.sgs.2022.11.002
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    With the rapid development of globalization, information and communication technology and high-speed railways, the frequency of element flow has greatly increased, and the comprehensive connection of multiple flow perspectives has become the key to the development of port cities and regions. With the help of GIS, Matlab and Gephi and other technical means, different flow elements are used to analyze the network connection and spatial variation characteristics of China’s coastal port city system in 2006 and 2016. The results show that: 1) In the 5 flow element networks, the total number of element connections between cities has increased and the increase degree has been larger, and the degree of concentration and dispersion and the characteristics of regional distribution have changed significantly. The cyberspace structure of the port city system is transforming from a ‘point axis’ model to a ‘networked’ model. 2) The hub cities with different flow elements have a high degree of overlap, but the network structure has obvious differences. Logistics and passenger flow present the network characteristics of coexistence of ‘group development’ and ‘hub-spoke’. The capital flow and technology flow have developed significant ‘core-periphery’ and hierarchical spatial patterns. Information flow presents a balanced network development model. 3) Different flow elements describe the port city system at different levels, but they are closely related. Logistics and passenger flow affect each other and are cause and effect. The flow of capital and technology has a positive effect on logistics. The impact of information flow on logistics has obvious lag; the port city system has changed from a single flow element to a comprehensive development of multiple flow elements, and the connections between port cities are more diversified, and the interaction and integration with external flow elements have been realized.

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    The Possibility Mechanism and Actual Estimation of Decoupling Between Port and City: Taking Port Cities of Bohai Rim as an Example
    Li Nan, Liu Enmei
    2022, 42 (11):  1879-1888.  doi: 10.13249/j.cnki.sgs.2022.11.003
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    Due to multiple conflicts derived from differences in objectives, port-city relations are no longer just a single situation of simultaneous rise and fall. Economic connection and spatial symbiosis are the basic support of the relationship between port and city, and with the transformation of urban industrial path and the migration of ports to open sea space, whether it is possible for urban development to break away from the dependence on port operation after entering a certain stage deserves special research. Therefore, the concept of port city decoupling was put forward for the first time, and the influencing factors and realization conditions of port city decoupling were revealed. Based on the theoretical exploration on the possibility of decoupling between city development and port operation, Tapio decoupling model was adopted to estimate the specific status. The evaluation systems of port and city were structured including the index of industrial diversification, the twelve samples of the main port cities of Bohai rim were selected to test the decoupling type empirically. The research shows that although the decoupling status of most port cities often change, the decoupling between port and city really become the impossible evolution path. Observed from the delineation and distribution of decoupling status of port cities around the Bohai Sea, the pattern shows alternating fluctuations of various types on the whole, and this is in line with the characteristics and facts of port city heterogeneity. Even if the decoupling between port city development and port operation become a reality, the course will be gradual. The influence factors of decoupling between port and city includes the development stage of port city, open economy level, industrial diversification, etc. The difficulty of decoupling is relatively small for two types of port cities, one is cities where port operation and local economy have not been deeply integrated, the other is central cities with strong economic strength and diversified development paths. According to the individual estimation of the dynamic possibility of port city decoupling in the case area around the Bohai Sea, Dandong and Qinhuangdao are already in decoupled state. There is a great potential for Tianjin and Qingdao to decoupling in the future, but the evolution of port city relationship in Dalian is not stable. The port city correlation of most samples such as Tangshan, Yingkou and Rizhao is still close, these cities are less likely to be decoupled. Most port cities will continue to explore between close dependence and alienation. At the policy level, it is necessary to regularly monitor the development status and trend of port cities.

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    Characteristics and Influencing Factors of Daily Population Flow Among Cities in China
    Shi Xiang, Wang Shijun, Wang Dongyan, Hao Feilong, Li Zhuowei
    2022, 42 (11):  1889-1899.  doi: 10.13249/j.cnki.sgs.2022.11.004
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    Using Tencent location big data, this study analyzes the spatial pattern of population flow among 368 cities in China and identifies the influencing factors related to population inflow and outflow based on an exponential random graph model (ERGM). 1) From 2015 to 2018, the spatial distribution pattern of population flow was relatively stable, forming a rhombic spatial structure with Beijing, Shenzhen, Shanghai, Guangzhou, Chengdu, and Dongguan as the ‘center’. The densely populated nodes and channels are mainly concentrated to the east of the Hu Huanyong Line. The significance of this study lies in further determining the core cities and main pillars in the population flow network. 2) The urban subgroup structure obtained by community division shows obvious geographical proximity and inter-provincial differentiation among communities, which form not only small urban subgroups with the provincial capital city forming the core and bordered by the provincial boundary, but also large urban subgroups with a multi-center structure spanning provincial administrative boundaries. However, for most cities, the provincial boundary delimits the main flow circle, and population flow within the same province is more frequent. 3) The influencing factors of the population inflow and outflow networks determined by the ERGM model are consistent with the predictions of neoclassical economics. Market and economic factors such as population scale, urbanization level, time cost, and economic cost still play a leading role in population flow. 4) The attraction of a city to the floating population depends on its individual attributes, while the urban population outflow depends more on the external-network-related elements of the city. To a certain extent, this study verifies the predominance of the urban “pull” in the push-pull theory and the comprehensive effect of various distance factors.

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    The Dynamic Change of Global Rare Earth Trade Network and Its Impact Mechanism: From the Perspective of Industrial Chain
    Zhuang Delin, Li Jiahao, Chen Ziruo, Liu Yuchen
    2022, 42 (11):  1900-1911.  doi: 10.13249/j.cnki.sgs.2022.11.005
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    From the perspective of rare earth industrial chain, this article successively constructed the rare earth primary processed products, intermediate processed products and finished products trade network according to the trade dependence, and empirical test on the dynamic change of rare earth trade network structure and its influencing mechanism by using social network analysis method and Temporal Exponential Random Graph Model. The following conclusions are drawn. The three types of rare earth trade network are evolving into a complex network, and the trend of the intermediate processed products goods network ahead of the finished products and primary processed goods network in turn. From the perspective of backbone structure, three types of rare earth trade network have evolved from Europe to Europe and the United States, from China to Europe and the United States, and from Europe, the United States and Asia to Asia. China evolves into the top three countries with direct influence in all networks, but its leading edge has gradually narrowed, while its indirect influence has only entered the top three countries in the network of primary processed products and finished products, with a small increase. Mutual, triangle, star-radiation and star-expansion structure effects have significant heterogeneous effects on the dynamic evolution of the three types of rare earth trade network.

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    The Impact of High-speed Railway on the Industrial Structure of County-level Units: Taking the Yangtze River Delta as an Example
    Shi Dehao, Yu Tao, Wang Lei
    2022, 42 (11):  1912-1922.  doi: 10.13249/j.cnki.sgs.2022.11.006
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    Along with the rapid construction and extent of the high-speed railway network, almost all prefecture-level cities have enjoyed high-speed railway services, especially in the southeast coastal region. Therefore, the main body of high-speed railway construction has been transferred from connecting prefecture-level units to county-level units. However, current studies have rarely paid attention to the impact of the high-speed railway on county-level units. The purpose of this article is to explore what changes will take place in the industrial structure of county-level units after the opening of the high-speed railway and its mechanism. Taking the Yangtze River Delta as an example, it was evident that the sequence of high-speed rail opening and the evolution process of industrial structure in this region have significant synchronization. With the usage of socio-economic panel data of all county-level units in this region from 2000 to 2017, this article measured the impact of high-speed railways on the industrial structure through the time-varying difference-in-differences model and employed sub-grouping, threshold effect and mediation model to explore the mechanism of high-speed rail effect. The results of the study are listed as follows: 1) The opening of the high-speed railway will promote upgrading the industrial structure of county-level units, which is composed of the dispersion of the secondary industry and the aggregation of the tertiary industry. 2) Population size has partial mediating effect on the high-speed rail effect, but there is no threshold mutation within the population size range of the counties and county-level cities in the Yangtze River Delta. 3) The secondary and tertiary industries have different time-laggings in the effect of the opening of the high-speed railway, resulting in two window periods for the transformation of the county-level unit industrial structure. When the county-level units apply for the high-speed railway project, it is necessary to judge their industrial characteristics prudently. And they should follow the law of industrial evolution after opening the high-speed rail and formulate targeted policies to encourage or hedge.

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    Ecological Security Assessment and Spatio-temporal Transition Characteristics in the Yangtze River Delta Urban Agglomeration
    Zhang Zhonghao, Nie Tiantian, Gao Yang, Tan Shenghui, Gao Jun
    2022, 42 (11):  1923-1931.  doi: 10.13249/j.cnki.sgs.2022.11.007
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    The PSR model, catastrophe progression method and exploratory spatial temporal data analysis are used to quantitatively characterize the spatial pattern of ecological security levels of 26 cities in the Yangtze River Delta urban agglomeration. This article has concluded three findings as follows. Firstly, the ecological security levels of the cities in the Yangtze River Delta urban agglomeration has increased from 2005 to 2015, but most cities are in the relatively unsafe and relatively safe level, and the overall ecological security level is not in the high level. Secondly, the spatial structure stability of urban ecological security level in the central and southeastern regions of the Yangtze River Delta urban agglomeration is better; Nantong has the greatest spatial dependence, while Shanghai has minimal spatial dependence; The analysis of the moving direction of LISA time path shows that the Yangtze River Delta urban agglomeration has strong spatial integration in the ecological security evolution. Thirdly, the spatial cohesion of Moran’s Ι is $ {K}_{t} $=0.698, that means the probability of no type transition is 69.8%, which indicates that there is a certain pattern change in the ecological security level of cities in the Yangtze River Delta urban agglomeration, but it is not easy for their relative position to change. This study discusses the coordinated growth mechanism of regional ecological security, which can provide a theoretical basis for the diagnosis and regulation of ecological security problems of urban agglomerations in the Yangtze River Delta urban agglomeration. Moreover, it also provides relevant reference for the sustainable development of other urban agglomerations.

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    Spatio-temporal Heterogeneity Characteristics of Industrial Ecological Transformation in Restricted Development Zones of Shandong from the Perspective of Multi-source Data
    Guo Fuyou, Gao Siqi, Zhang Quanjing, Zhang Yanjun, Jiang Zhengju
    2022, 42 (11):  1932-1942.  doi: 10.13249/j.cnki.sgs.2022.11.008
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    The comprehensive evaluation of industrial ecological developing transformation and the diagnosis of obstacle factors for the restricted development zone of Shandong Province are important basis for promoting the conversion of new and old kinetic energy and regional sustainable development in Shandong Province. Based on the scientific connotation of industrial ecological transformation, this article constructed a measurement framework and model from two aspects of the development status and the transformation extent, and then evaluated the spatial-temporal evolution pattern and influencing factors of industrial ecological transformation performance in the restricted development zone from 2006 to 2018. The results show that: 1) The development status rises first and then declines during the study period, and the total level of development status changes not obvious indicating that the industrial ecology development in the restricted development zone is characterized by robustness; the proportion of counties with excellent and poor transformation extent remains stable at about 50%, it reflects that the intensive and connotative industrial development path has obtained certain results in recent years, while it also has not yet changed the essence of negative interactions between the industrial system and the ecological environment in the restricted development zone. 2) In general, the performance of industrial ecological transformation makes a little progress within the study period, and the spatial distribution of it is higher in the east of Shandong and lower in the west, this polarized development pattern has become more prominent over time; in addition, the industrial ecology development status has made a greater contribution to the improvement of transformation performance, and the transformation extent has not yet been an important driving role. 3) The main obstacle factors affecting the process of industrial ecological transformation are general budgetary revenue of local finance, the greening area, urban and rural household savings deposits, total retail sales of consumer goods and dependence on foreign investment.

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    Spatial-temporal Evolution and Convergence Trend of Air Quality in China’s Urban Agglomerations
    Wan Qing, Luo Xiang, Pan Fangjie, Jin Gui
    2022, 42 (11):  1943-1953.  doi: 10.13249/j.cnki.sgs.2022.11.009
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    Based on the real-time monitoring data of China’s urban air quality from 2015 to 2020, the paper quantitatively analyzed the air quality differences in urban agglomerations and their sources and convergence mechanisms, using methods such as Dagum Gini coefficient, coefficient of variation and convergence model. The results show that: 1) Since 2015, the air quality of China’s 20 urban agglomerations has not shown an ideal trend of improvement year by year, but the air quality of most urban agglomerations tends to improve in the process of fluctuation, and O3 has begun to replace PM2.5 as the most important primary pollutant in part of urban agglomerations. 2) The spatial differentiation characteristics of air quality in China’s urban agglomerations are obvious, but the spatial differences have been reduced during the study period, and the differences between urban agglomerations are much larger than those within urban agglomeration. 3) The air quality of China’s urban agglomerations not only has a trend of σ convergence, but also a trend of absolute and conditional β convergence. Whether or not other heterogeneous influencing factors other than the initial air quality are considered, the urban air quality within each urban agglomeration is moving towards steady-state level.

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    Similarity of Spatio-temporal Behavior of Tourists in Island-based Destinations Based on GPS Data: A Case Study of Changdao Island in Shandong Province
    Hu Yuna, Ma Xintao, Liu Jisheng, Liu Yongwei
    2022, 42 (11):  1954-1962.  doi: 10.13249/j.cnki.sgs.2022.11.010
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    In this article, the similarity characteristics of tourists’ spatio-temporal behaviors were studied by crawling the GPS track data of two major platforms, Two Steps and Six Feet, using kernel density analysis, spatial gridding, and in-off-track analysis, taking Changdao Island in Shandong Province as an example. The following conclusions were obtained: 1) Within the year, under the influence of climatic factors, the seasonal intensity index is higher in island-type destinations, showing stronger seasonal similarity; 2) Within the day, the ‘double peak’ structure of the number of trajectories and the “triple peak” structure of the length of trajectories both indicate strong similarity and concentration of tourists’ travel time and trajectory length, in addition, compared with the general destinations, the end time of tourists’ trips in island-type destinations is relatively later. 3) Spatially, the inconvenience of transportation and time constraints cause a high concentration of tourists in the choice of islands. The ‘seaward’ trajectory of tourists is very prominent, and the length of stay in areas where tourists can engage in water-based activities, such as beaches and coastal plazas, increases significantly, and ‘sea’ is the most attractive element for tourists. Therefore, compared to the ‘radial’ or ‘cluster’ structure of land-based urban destinations, island-based destinations have a typical ‘axial’ and ‘circular’ structure. The island destinations have a typical ‘axis’ and ‘ring’ structure with a high concentration of trajectories. For island destinations, how to build their own ‘golden’ coastal landscape, ‘sea-friendly’ tourism products and coastal tourism service facilities with high quality is a very important issue. Similar to other types of destinations, most tourists have a high rate of on-trail travel during the tour, which means that their behavior is largely constrained and regulated by the road, so the reasonable planning and design of tourism paths are very important in guiding tourists’ spatial behavior, and the high connectivity of paths helps tourists form effective flows between different locations. 4) The central role of scenic areas is not as prominent on islands compared to other types of destinations. This poses three major challenges to the management of island-type destinations: First, the high overlap rate with local residents in the use of public transportation facilities and public leisure space during the peak tourist season, and the phenomenon of overcrowding in some road sections and leisure spaces, which not only reduces tourist satisfaction, but also often triggers conflicts between residents and tourists, forming some social problems; second, the revenue of scenic spots is not high; third, tourists stay on the island for a shorter period of time. The phenomenon of ‘prosperity but not wealth’ is more prominent. Therefore, island-type destinations should focus on differentiation and experience in the planning and design of scenic products, so that only when tourists expect a different tourism experience can they be successfully attracted to the scenic spots.

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    Evolution Characteristics and Formation Mechanism of Territorial Space Pattern in Guangxi Zhuang Autonomous Region
    Lin Shugao, Lu Rucheng, Ye Zongda, Liu Shaokun, Bao Bojian, Deng Shiyu
    2022, 42 (11):  1963-1974.  doi: 10.13249/j.cnki.sgs.2022.11.011
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    The evolution and formation mechanism of territorial space pattern is a scientific question of the study on human-earth system interaction, and it is the key premise of territorial space planning. The Geo-graphic, Standard deviation ellipse model and Spatial autocorrelation method were performed to analyze the evolution characteristics of territorial spatial pattern in Guangxi Zhuang Autonomous Region from 2000 to 2018, and the Geographic detector was used to reveal the formation mechanism. The results show that: 1) The urban space area increased, while the area of agricultural space and ecological space decreased in Guangxi Zhuang Autonomous Region. In addition, the expansion of urban space was consistent with the contraction of agricultural space and ecological space, and the dynamic changes of territorial space accelerated. 2) The territorial space transformation of Guangxi Zhuang Autonomous Region was frequent, and there was a significant diversity of the transfer trajectory It means that the exchange between agricultural space and ecological space and the reorganization of the internal structure of ecological space were accelerated. 3) The migration path of territorial space was dominated by the interaction between urban space and agricultural space in Guangxi Zhuang Autonomous Region. The agglomeration characteristics of urban space and agricultural space showed ‘high in the south and low in the north’, and that of ecological space were ‘high in the north and low in the south’. 4) The evolution of territorial space pattern was influenced by the joint action of physical geography and socioeconomic factors in Guangxi Zhuang Autonomous Region. The limiting effect of natural environmental conditions was gradually weakened, while the driving force of socioeconomic development level and the intensity of policy regulation played a far-reaching role. Therefore, the spatial pattern of Guangxi Zhuang Autonomous Region can be optimized through territorial spatial planning, adjustment of industrial layout and guidance of production and life style.

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    Dynamic Evolution Path of Land Use in the Hinterland of the Three Gorges Reservoir Area: A Case Study of Fengjie County
    Xia Chunhua, Li Yangbing, Chen Shuang, Huang Mengqin, Tang Jinjing, Wang Ruofeng
    2022, 42 (11):  1975-1985.  doi: 10.13249/j.cnki.sgs.2022.11.012
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    This article took Fengjie County in the hinterland of the Three Gorges Reservoir Area as the study area, based on the land use data in 1980, 2000, 2010 and 2020, analyzed the dynamic change process of land use in Fengjie County from the “whole region-local” scale by adopting the methods of dynamic degree of single land use, regional division and land use pattern division, cleared the evolution path of land use and explored its driving mechanism. The results showed that: 1) The overall performance of land use change in Fengjie County and other small areas was consistent from 1980 to 2020; forest land, orchard, abandoned land and urban and rural settlement land continued to increase, while grassland, shrub land and cultivated land continued to decrease. 2) The land use evolution of Fengjie County tended to be ecological conservation, while the small areas were mainly manifested as single grain supply type and eco-economic cooperation type, comprehensive development of grain supply and eco-economic cooperation type, and gradual transition from grain supply to eco-economic cooperation type. 3) The land use evolution of Fengjie County was influenced by the comprehensive role of natural, the construction of the Three Gorges Project, socio-economic and policy factors from 1980 to 2000, and the land use was mainly affected by the construction of the Three Gorges Project, socio-economic and policy factors from 2000 to 2010, while it was mainly restricted by socio-economic and policy factors from 2010 to 2020.

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    Livelihood Vulnerability and its Influencing Factors of Geographical Indication Agricultural Products Growers: A Case Study of Mei County and Zhouzhi County, Shaanxi Province
    Feng Xiao, Shi Xingmin, Fan Yi, Chen Xieyang
    2022, 42 (11):  1986-1995.  doi: 10.13249/j.cnki.sgs.2022.11.013
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    Geographical indication agricultural products play a significant role in promoting the greener and high-quality development of agriculture, rural revitalization and improving the livelihoods of growers. The increase in climate change and extreme weather events may exacerbate the livelihood vulnerability of geographical indications growers. This study takes the geographical indication agricultural products kiwifruit planting area as an example. A livelihood vulnerability assessment framework combining with the entropy method and the Jenks natural break method were used to assess the livelihood vulnerability of growers. Ordinal Logistic regression and Shapley value decomposition method were used to explore the influencing factors and their contribution to the livelihood vulnerability of the growers, respectively. The results show that: 1) The proportion of growers in the middle and high vulnerability levels is relatively large, accounting for about 64.10%. 2) The contribution rate of the production characteristics of the growers to the livelihood vulnerability level is 48.47%. Whether to use geographical indication trademarks, whether to participate in geographical indication trademark training, and whether to adopt cooperative production has a significant impact on the livelihood vulnerability of growers. 3) In terms of planting characteristics of growers, planting time has a significant impact on the level of growers’ livelihood vulnerability, with a contribution rate of 12.20%. 4) In terms of the intensity of adaptation behavior, the adoptive intensity of continuous autumn rain has a significant impact on the livelihood vulnerability of kiwifruit growers, with a contribution rate of 20.75%.

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    Spatial and Temporal Explicit Analysis of Forestland of Northeast China in 1950-2020
    Yang Xuhong, Jin Xiaobin, Yang Yongke, Xue Qiaofeng, Liu Ronggao, Zhou Yinkang
    2022, 42 (11):  1996-2005.  doi: 10.13249/j.cnki.sgs.2022.11.014
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    The abundant forest cover information has been recorded on the historical topographic maps which can offer the first-hand information of long time period of forest cover change and satisfy the research of land cover reconstruction and its environmental effect. By the meaning of map interpretation and data digging, this study has extracted the forestland cover information from historical topographic maps (1950) and contemporary land use map (2020), and analyze the change process and spatial-temporal pattern of forestland cover during 1950 to 2020. The results showed that: 1) It is very accurate for the forestland cover information recorded in the historical topographic maps which can effectively represent the fundamental spatial-temporal pattern characteristics of forestland in Northeast China in the middle of 20th century; In the past 70 years, the total area of forestland in Northeast China had rapidly increased by 10.04×104 km2, and meanwhile the forestland coverage ratio had increased from 34.67% to 44.97%. Except Baishan City, the area of forestland in the cities level is increasing and the forestland area of net growth of top five cities have exceeded 5 000 km2. 2) During the study period, the region areas of maintained, increased and decreased forestland were 28.36×104 km2, 15.49×104 km2 and 5.45×104 km2 respectively. The maintained region for forestland mainly were distributed on the Changbai Mountains, the Lesser and Greater Khingan Mountains which have spatially formed the inverted U-shaped pattern, and the area have covered the 64.68% of whole forestland in 2020. The increasing district of forestland was concentrated in the Liaohe Plain, the west of Changbai Mountains, the east side of the Sanjiang Plain and the east-east sides of Da Hinggan Mountains, and the decreased region of forestland was scattered in many place. 3) The region disappeared the forest have been mainly occupied by the grassland and grain farming which have accounted for the 88.18% of whole decreased forestland area, and it is basically equal for the forestland occupied by waterbody or urban-rural construction, accounting for about 2.00% of whole decreased area. 4) The site condition and quality of forestland have been greatly improved. On the one hand, the average distance from forestland to the nearest towns has shrunk by 2.26 km, and more than half of the newly increased forestland have located the region within no more than 10 km distance to the towns, and it means the forestland have spatially expanded to the near center of town. On the other hand, the average elevation of forestland has been decreased by 41.44 m, and more than half of the newly increased forestland have concentrated the region within 300 m elevation above the sea level, which means the increasing forests have grown on the plains and gentle slopes region.

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    Impact of Population Changes on County Economic Vulnerability in the Loess Plateau
    Yuan Qianwen, Chen Jia, Han Wenwei, Yang Xinjun
    2022, 42 (11):  2006-2018.  doi: 10.13249/j.cnki.sgs.2022.11.015
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    Population and economic development is important research contents in the field of sustainable development, and is an important carrier for realizing rural revitalization and regional high-quality development. In order to promote the high-quality development of the Loess Plateau region, it is necessary to have a new understanding and judgment on the relationship between population and economic vulnerability in the region of the Loess Plateau. This paper takes the county of Loess Plateau region as an example, utilizes the sensitivity-resilience model to evaluate the characteristics of economic vulnerability and its temporal and spatial changes in the Loess Plateau since 2000, and explores the effect of population changes on county economic vulnerability by ArcGIS spatial technology and gray correlation analysis. The results are as follows: 1) In 2000, the economic vulnerability grades of counties in the Loess Plateau were dominated by low and lower vulnerability grades, while in 2010, the area of low vulnerability areas decreased, and the areas of medium and high vulnerability increased significantly. In 2017, the area of low and low vulnerability grades increased, and the area of medium and high vulnerability areas decreased. In general, from 2000 to 2017, the overall economic vulnerability of counties in the Loess Plateau showed a significant trend of ‘increase first and then decrease’. 2) The overall economic vulnerability of the county in the Loess Plateau shows the spatial pattern of “high in the south and low in the north”. The counties with high and relatively high levels are mainly concentrated in the area of Liupan Mountains and Luliang Mountains; the middle-level counties are concentrated in the area of Longdong, Taihang Mountains and Luliang Mountains; the vulnerability level of the surrounding areas of counties, districts and prefectures under the jurisdiction of the provincial capital city is the lowest. 3) The population outflow rate, gender ratio, and the proportion of the elderly population, which represent population changes, are the key factors affecting the county economic vulnerability of the Loess Plateau, and the influencing factors of population changes on economic vulnerability in different periods are different.

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    Evaluation of Reconstruction Effect of NDVI Time Series Based on QA Weight: A Case Study of MODIS NDVI in the Yangtze River Basin
    Zhu Hui, Hu Yong, Sun Fen, Wang Qiang, Ma Xueying
    2022, 42 (11):  2019-2027.  doi: 10.13249/j.cnki.sgs.2022.11.016
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    In this article, the quality of MODIS NDVI in the Yangtze River Basin is analyzed by calculating the mass frequency and noise ratio. Based on three commonly used reconstruction methods of S-G, A-G and D-L, three quality weight schemes are designed to reconstruct the time series MODIS NDVI data of the Yangtze River Basin from 2001 to 2020. Subsequently, the reconstruction effect is analyzed and evaluated by visual contrast, high-quality regional fidelity as well as simulation denoising. The results show that the annual noise ratio in the Yangtze River Basin is mainly 75%?125%, in which the noise in winter has a great inhibitory effect on NDVI, followed by spring and autumn, and the noise in summer has an increasing effect on NDVI. The S-G method on the basis of the third quality weight scheme exerts the optimal effect on the reconstruction of continuous missing original data. Additionally, in the high-quality region, the fidelity of A-G method is high, and the mean R2 and RMSE of high-quality pixels are 0.9489 and 0.0245, respectively. Moreover, in the simulation denoising experiment, the S-G method has the least data loss pixels after reconstruction, the average value and standard deviation of the R2 between the reconstructed data and the original data are 0.8616 and 0.1848 respectively the RMSE is between 0.0035 and 0.4411, and the standard deviation is 0.0383, indicating that the fidelity of the S-G method is higher in the low-quality area.

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    Layout and Optimization of Urban Water System Connectivity Based on the Graph Theory
    Fu Chun, Deng Junpeng, Ouyang Huanrui, Fu Yaozong, Zhang Jing
    2022, 42 (11):  2028-2038.  doi: 10.13249/j.cnki.sgs.2022.11.017
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    Urban expansion has cut off the originally connected rivers and lakes, and repairing the connectivity of the water systems in urban areas is an important part of the construction of sponge cities and water ecological civilization cities. Based on the ‘point-edge’ quantitative relationship in landscape ecology, three water system connectivity evaluation indicators (α), node connection rate (β) and network connectivity (γ) are established, and the ‘node-corridor’ of the water system in Nanchang is drawn. ‘Tao’ has a directed map and uses urban lake water drainage and pollution as the starting point to optimize the connectivity of the urban water system. Studies have shown that: 1) The urban water system of Nanchang has uneven distribution of corridors, and there are fewer corridors connecting the lake node with other water system nodes; 2) The optimized urban water system is compared with the current water system. The degree (α) is increased by 75%, the node connection rate (β) is increased by 14.88%, and the network connection degree (γ) is increased by 14.63%. In the optimization of urban water system connectivity, we should not blindly increase lake corridors by pursuing connectivity too much. We should maintain a balance between connectivity and the number of corridors connected to the lake to prevent water pollutants from silting up in the lake.

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    Permeability and Brine Enrichment Mechanism of Brine Reservoir in the Mahai Salt Lake, Qaidam Basin
    Hu Shuya, Ren Jie, Li Jiqing, Zhao Quansheng
    2022, 42 (11):  2039-2046.  doi: 10.13249/j.cnki.sgs.2022.11.018
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    The permeability coefficient of brine reservoir in the Mahai Salt Lake of Qaidam Basin was determined by field pumping test, and its permeability was analyzed by the occurrence characteristics and sedimentary environment of underground brine. The results showed that most of the rock salt layers in this area are impure, the rock salt crystals are wrapped with mud and sand, and the crystals are also filled with mud and sand. During the period of rock salt deposition, the permeability of the brine reservoirs formed during the evolution of the geological environment varied considerably due to the influence of floods and intermittent rivers, and the connectivity of the regional subsurface brine was weak. According to the drilling data of 27 mining wells and the monitoring data of underground brine in the experimental mining area, the brine reservoir was classified differentially. The brine reservoirs exposed by the drilling were divided into three types. The brine enrichment performance of different types of brine reservoirs is quite different. Through the analysis of the lithology, pore characteristics and supply conditions of borehole cores, the basic conditions for strong brine enrichment performance were obtained: The brine reservoir has a natural good particle skeleton and a stable brine supply source and channel. According to the permeability of brine reservoir and the law of brine enrichment, the experimental mining area of the Mahai Salt Lake was divided into different underground brine enrichment sections.

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