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    Remote Sensing Image Segmentation Using Dual Attention Mechanism Deeplabv3+ Algorithm
    Liu Wenxiang, Shu Yuanzhong, Tang Xiaomin, Liu Jinmei
    Tropical Geography    2020, 40 (2): 303-313.   doi: 10.13284/j.cnki.rddl.003229
    Abstract675)   HTML6)    PDF (25841KB)(148)      

    Remote sensing image processing technology based on deep learning can prospectively be used to determine the characteristics of large numbers of remote sensing image data and complex scenes. However, deep-learning algorithms in remote sensing image processing have certain shortcomings, e.g., the popular DeepLabv3+ network has slow fitting speeds, inaccurate edge target segmentation, inconsistencies, and holes in large-scale target segmentation. We therefore proposed a method for introducing a Dual Attention Mechanism Module (DAMM) to DeepLabv3+ to address the above deficiencies. We designed two different network models that connected the DAMM structure to the Atous Spatial Pyramid Pooling (ASPP) layer in series or parallel. In the serial connection method, the feature map was first sent to the DAMM and then passed through the ASPP structure. Furthermore, the feature map was defused with middle-low layer feature information through the decoder layer and restored to the original image resolution. In the parallel connection method, the DAMM and ASPP layers processed the feature map extracted from the backbone network in parallel and subsequently fused the processed feature map information. The mixed feature map was restored to its original resolution by the decoder. The two improved methods were verified by the INRIA Aerial Image high-resolution remote sensing dataset. The results showed that both the series and parallel methods could effectively improve the shortcomings of Deeplabv3+. The experimental results showed that the parallel network had superior performance, and improvements in the original network defects were more obvious. The parallel method achieved a higher score [85.44% Mean Intersection Over Union (MIOU)] in the test dataset, which was 1.8% higher than Deeplabv3+. And the serial network increased by 1.12% compared to Deeplabv3+. The effects of the position and channel attention mechanisms in the DAMM structure were also determined. The ablation study results showed that the channel and position attention mechanisms improved the performance of the Deeplabv3+ model. In the test set, the channel and position attention mechanism mIoU increased by 0.95 and 1.32%, respectively. The experiments revealed that the position attention mechanism had a greater effect on edge target segmentation, the channel attention mechanism had a greater effect on large-scale hole phenomena, and the channel and position attention mechanism promoted network fitting speed in training. The proposed improved DeepLabv3+ algorithm can provide a scientific basis and reference for semantic segmentation of big data remote sensing images.

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    The Impact of COVID-19 on China’s Economy and Discussion of Policies‒Evidence from Listed Companies
    Zhang Kaihuang, Qian Qinglan
    Tropical Geography    2020, 40 (3): 396-407.   doi: 10.13284/j.cnki.rddl.003252
    Abstract503)   HTML12)    PDF (1011KB)(194)      

    The Corona Virus Disease 2019 (COVID-19) has collapsed the world’s economy. A discussion of the reaction to structural and regional policies is imperative for the Chinese government because the implementation of policies is limited. As the state of the stock market indicates the direction of the economy, the financial reports of some enterprises from China’s Stock market for the first quarter of 2020 were collected and analyzed. This was the period in which the productivity of the enterprises were severely impacted by the coronavirus pandemic with respect to industry, actors’ scale, and region. The results show: 1) Except agriculture, forestry, animal husbandry, and fishery, all other industries had lesser profit and limited operating cash flow, and their balance sheets had deteriorated. The services industry faced more challenges than the others. The behavioral decisions made by individuals, the governmental policies for lock-down, and the nature of industries were responsible for these detrimental changes; 2) The companies with small and medium market value were affected more than big enterprises. In Q1, big companies made more profits, optimized their operating cash flows, and stabilized their balance sheets. This is mainly because of the difference of operating ability among actors and the Matthew effect; 3) Owing to the differences in the population structure and land price in different regions, the manufacture, service, and building and estate industries faced greater challenges in the developed provinces than in the less developed regions. The pandemic adversely affected the finance industry in Beijing, Shanghai, and Guangdong; however, it showed improvement in Jiangsu. It has been observed that the financial structure in regions, and operating ability of companies were the main reasons for the negative impact on the finance industry. The medical industry was affected but progressed in areas with better industrial basement. This was because the demand for certain medicines and devices peaked during the period and the areas with better industrial base played more important role in fighting the virus. In this context, the authors discussed the two approaches: “Adopting a more proactive fiscal policy and deeply optimizing financial environment of enterprises,” and “Choosing policies implements regionally.” It can be argued that unilateral expansion of demand will result in a larger gap between demand and supply. This is disadvantageous because the global production system mainly depends on the manufacturing industry in China. The government should not only focus on resumption, but also start investment of new or traditional infrastructures. Moreover, owing to the uncertainty of the market, the factors that improve the balance sheet are few. Therefore, helping more entities by financial market and making the social capital more active have become the priorities for the government. In order to improve the manufacturing and service industry, undeveloped regions are encouraged to expand job opportunities, and the residents in developed regions are encouraged to consume more services and decrease the operating costs of the service industry. This can positively contribute to restoring the economy. Some measures adopted to benefit financial and building and estate industries are encouraging local commercial banks in medium-sized and small cities to provide loans to Small and Medium-Sized Enterprises (SMEs), boost infrastructure construction in developed regions, and loosen control of estate development. The policy makers of the medical industry were advised to focus on long-term development. Optimizing the financial environments for SMEs in medical industry and developing a multi-core, nation-wide distribution of industry are necessary for China.

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    Spatial Relationship between Epidemic Spread and Population Outflow of the Corona Virus Disease 2019 (COVID-19) That Impacted Chinese Urban Public Health Classification
    Xiang Yunbo, Wang Shengyun
    Tropical Geography    2020, 40 (3): 408-421.   doi: 10.13284/j.cnki.rddl.003247
    Abstract343)   HTML10)    PDF (2337KB)(120)      

    Population mobility affects the spread of the new coronavirus and of risk. Based on Baidu migration big data and provinces and municipalities’ health committee data, combined with geographic information technology, this paper studies the spatial relationship between the spread of Corona Virus Disease 2019(COVID-19) in 136 cities from January 1st to March 5th, 2020, and the outflow of population in Wuhan, which impacted urban public health management in China. The following results were obtained. The spread of COVID-19 in China has the following stages and characteristics: occurrence and recessive spread, rapid spread and outbreak, diffusion containment, and diffusion attenuation. From January 1st to March 5th, 2020, it was observed that the population flow of Wuhan City mainly extends to the Hubei Province and its surrounding provinces and cities, as well as Beijing, Shanghai, Guangzhou, Shenzhen and other first-tier cities, with geographical proximity and characteristics similar to regional central city population inflow. Influenced by geographical distance, time cost, social and economic connection, overseas input, and so on, the spatial distribution of COVID-19 is evidently unbalanced. The urban agglomeration in the middle reaches of the Yangtze River, the Beijing-Tianjin-Hebei urban agglomeration, the Yangtze River Delta urban agglomeration, Guangdong-Hong Kong-Macau Greater Bay Area, and the Chengdu-Chongqing urban agglomeration have become key areas for the concentrated distribution of COVID-19. Additionally, some key entry and exit port cities present a higher risk of spreading. A strong positive grade correlation between epidemic spread and population outflow is observed with COVID-19. The spatial relationship between the two can be divided into eight regulation types. Nearly 90% of cities have the characteristics of large population inflow, high numbers of confirmed cases or small population inflow, and low numbers of confirmed cases. Among these, cities with large population inflow and high numbers of confirmed cases are mainly concentrated in the Hubei Province and central cities of key urban agglomerations in China. The pressure of prevention and control stems from the risk of epidemic spread, caused by a large population inflow and high number of confirmed cases. The urban distribution, with a small population inflow and low number of confirmed cases, is scattered, and the difficulty involved in prevention and control is the improvement of the precision of such countermeasures. Although China’s strategies for epidemic prevention and control have achieved remarkable results, considering the evolution of the global epidemic situation, rebound uncertainty still exists, and external defense input as well as internal defense rebound pressure are still very heavy. Currently, and in the future, the prevention and control of the epidemic situation will become the “new normal” with the economic and social development of our country. Improving the capacity for urban public health management is necessary for the prevention and control of the epidemic situation in China, especially in the future. Chinese epidemic prevention and control should still consider local conditions and formulate targeted prevention and control strategies. In particular, it is necessary to consider the relationship between the spread of COVID-19 and population flow, economic ties, transportation costs, international exchanges and other factors, and set specific classifications and control plans. To facilitate the joint prevention and control strategy to formulate full coverage, and “Not One Less,” we should not only approach the current epidemic prevention and control it from a dynamic perspective, but also consider epidemic prevention and control work in specific types of cities. Urban agglomeration areas and port cities often have a large population inflow, frequent economic ties, high economic development pressure, and high-risk epidemic prevention and control. They bear the dual responsibility of economic and social development, stability, epidemic prevention, and control and management. In the context of resuming production, work, and economic and social recovery, special attention should be paid to the regular prevention and control of the epidemic situation as well as the improvement of urban public health management capacities.

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    The Impacts of COVID-19 on the Connectivity of China's International Air Transport Network and the Spatial Differences
    Du Fangye, Wang Jiao'e, Wang Han
    Tropical Geography    2020, 40 (3): 386-395.   doi: 10.13284/j.cnki.rddl.003248
    Abstract319)   HTML7)    PDF (2576KB)(88)      

    Air transportation plays an important role in connecting countries and promoting global economic development. Recently, China’s international air transport network expanded rapidly in terms of navigable countries and cities and the number of air routes and flights. In this context, the connectivity and stability of the air transportation network attracted significant attention, which could be threaten by many factors such as public health emergencies, poor weather conditions, policies, etc. Focusing on COVID-19, this paper depicted the spatial patterns of canceled flights after the spread of the COVID-19 pandemic across Chinese cities and the impact on connected countries and cities overseas. Next, this paper investigated the impacts of public health emergencies on the connectivity of China’s international air transportation network by comparing the changes of the average shortest path and weighted average shortest path before and after the outbreak of the COVID-19 pandemic. The results could be summarized as follows. First, the spread of this pandemic has significantly impacted the connectivity of China's international air transport networks. The number of navigable cities, routes and flights has substantially reduced, as has the efficiency of China's international air transportation. However, the COVID-19 pandemic has not significantly influenced the worldwide air transport network in this period. Additionally, the degree of effect of COVID-19 on air transportation connection was various across regions. For example, the air route suspension has the greatest impact on China's aviation network connectivity with Central Asia, West Asia and Oceania, while flight reduction has the greatest impact on China's aviation network connectivity with Northeast Asia, Central Asia and Southeast Asia. Second, there are no significant differences between the spatial patterns of the connectivity of China’s international air transportation network before and after the outbreak of the COVID-19 pandemic; the connectivity between China and Northeast Asia, Southeast Asia, North America, and Europe remains better than other areas. The findings indicate that labor mobility, economic communication, and trade are vital in shaping the spatial pattern of the connectivity of China’ international air transport network. However, the flight aggregation degree for international flights has increased. The proportion of flights among the top 5 countries has increased from 58.1% to 67.2%, which is also closely related to factors such as the proximity and necessity of personnel, economy, and trade links. The international route networks in Beijing, Shanghai and Guangzhou are more reliable than other cities. Thus, following the outbreak of COVID-19, the distribution of China’s international routes and flights has been concentrated in these major cities. The proportion of international air routes increased from 28.8% to 38.9%. Moreover, the concentration of international flights increased from 46.6% to 76.4%, which is a higher concentration than international air routes. While expanding its focus on the depth and breadth of international air transport links, China should focus on strengthening the reliability of international air transportation networks to cope with the impact of various emergencies and ensure basic connectivity and stable operation of international air transportation networks.

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    Identification and Patterns of Employment and Residential Centers in a Cross-Border Region Based on Mobile Phone Signaling Data: A Case Study of Guangzhou and Foshan
    Li Ying, Chen Tingting, Li Xun, Xu Weipan, Lang Wei
    Tropical Geography    2020, 40 (2): 206-216.   doi: 10.13284/j.cnki.rddl.003211
    Abstract296)   HTML14)    PDF (4526KB)(85)      

    Based on mobile phone signaling data, this study uses the Guangzhou-Foshan area as the focus area of a case study. The spatial structure is determined using the Lorenz method, and the spatio-temporal characteristics of job-housing are analyzed in a cross-border region. The findings of the study are as follows. First, the job-housing space of Guangzhou exhibits the characteristics of a single employment center and suburbanization, which is mismatched. The job-housing space of Foshan is mixed and presents a spatial pattern of "large scatter, small cluster," which is related to the urban development mode. Second, the job-housing space presents a new trend that emerged after the cities of Guangzhou and Foshan were integrated. The cross-border region, including Jinshazhou, Fangcun, and Guicheng, has formed a continuous high-intensity commuting area. Third, the job-housing patterns of the five cross-border regions are quite different. The Huadu airport area and the new station area (also referred to as a traffic hub type) support the airport economy and the high-speed rail economy, which affects the flow of labor and capital factors in the two cities and drives industrial development of surrounding areas. At the center of the cross-border region, the Jinshazhou and Fangcun-Guicheng regions (living type) undertake the resident spillover of Guangzhou and Foshan. The Wusha region (industry type) has a geographical advantage of forming a cross-border industrial park, attracting nearby residents for work. This research provides meaningful guidance and practice for the development of cross-border regions. Further, it provides new analytical dimensions and perspectives for related research. It can be seen that the development of different types of transboundary areas is conducive to suturing space rifts between the cities of Guangzhou and Foshan, thereby accelerating the integration of urban space. Based on the Lorenz curve, this study innovatively introduces a stricter endogenous threshold method to determine the threshold value of vocational and residential centers of Guangzhou and Foshan. Existing research mainly focuses on Beijing, Shanghai, Shenzhen, and other big cities. From the perspective of regional functions, this study focuses on cross-border regions and aims to provide references for regional coordinated development. However, some deficiencies still persist in this study, such as one person with multiple phone numbers, or incomplete samples of mobile phone signaling data. In the follow-up study, other trajectory data such as subway use and traffic can be added for verification. In addition, if the economic and social attributes of individual residents can be combined, the characteristics of people residing in cross-border areas during urbanization can be analyzed more precisely. This will be conducive to identifying patterns inoccupation and residence space.

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    Identifying Changes in Urban Spatial Structure Using Taxi Trajectory Data:
    A Case Study in Shenzhen
    Zhuang Haoming, Liu Xiaoping
    Tropical Geography    2020, 40 (2): 217-228.   doi: 10.13284/j.cnki.rddl.003224
    Abstract281)   HTML14)    PDF (30576KB)(62)      

    The concept of urban spatial structure refers to the inherent structure formed by interactions between people and places. Studying urban spatial structure (especially its dynamic characteristics) is of considerable significance for understanding and managing cities. This study characterized the long-term dynamics of an interaction-based urban spatial structure using a large-scale taxi trajectory dataset from Shenzhen, China, for May 2009 and September 2016. Spatial networks were built to model intra-city spatial interactions at different times in order to extract the dynamic spatial structure. Due to the differences between the global spatial structure and the local spatial structure of the city, two-level hierarchical spatial networks were built by separating long- and short-distance trips. The cut-off point for hierarchical partitioning was set as 5 km in both 2009 and 2016 by comparing the coefficient of determination (R 2) for the fitted probability distribution functions of the trip distances. Furthermore, the Infomap community detection algorithm was applied to detect global and local spatial communities in the network. By comparing changes in spatial communities and combining remote sensing images with planning policies, this study characterized dynamic changes in Shenzhen’s long-term multi-scale spatial structure and revealed the impacts of infrastructure construction and planning policy on the urban spatial structure. The results showed that the spatial structure of Shenzhen underwent dramatic changes from 2009 to 2016. 1) On a global scale, urban spatial structures tend to be compact. For example, numerous small spatial communities in the suburbs of Shenzhen have merged into five large spatial communities the same as planned functional clusters, which has relevance to the Shenzhen 2020 master plan. 2) The spatial form of communities has also undergone significant changes on a global scale. For example, the shape of the community connecting the Shenzhen urban area and Shenzhen airport has changed from “|” to “U”. This is related to the opening of the Guangshen Yangjian Expressway and the expansion of the Shenzhen airport, reflecting the impact of major transportation infrastructure development on the urban spatial structure. 3) On a local scale, urban spatial structures tend to develop in a polycentric manner. For example, in Shenzhen, the two spatial communities surrounding the North High-speed Rail Station and the Nanshan Center were split into multiple spatially small communities, indicating a strong relationship with major infrastructure construction and economic development. This study verified the effectiveness of Shenzhen’s administrative division adjustment, 2020 master plan, high-speed railway station, airport expansion, and arterial expressway construction from 2009 to 2016. The results provide a valuable reference for planning implementation assessment and impact assessment of infrastructure construction, providing support for urban traffic management.

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    A Spatial-Temporal Pattern Evolution Analysis of Urban Scale Development in the Guangdong-Hongkong-Macao Region Based on Nighttime Light Imagery
    Zhao Lixian, Li Changhui, Song Yang, Li Xi
    Tropical Geography    2020, 40 (2): 243-253.   doi: 10.13284/j.cnki.rddl.003231
    Abstract279)   HTML15)    PDF (6056KB)(90)      

    Taking the Guangdong-Hongkong-Macao region as our study area, we first used the time series data fitting method in TIMESAT to improve the quality of VIIRS nighttime light remote sensing images. We then generated annually averaged nighttime light images from the repaired VIIRS monthly composite data from June 2012 to May 2019. These, combined with the LandScan TM population distribution map and administrative division data, were used to analyze the spatial and temporal patterns of urban development in the Guangdong-Hongkong-Macao region for the first time, using a spatial statistics method, rank-size distribution method, and the Nighttime Light Development Index (NLDI) constructed using the Gini coefficient. The experiment was performed at both prefecture and county levels. The following conclusions can be drawn from this study. 1) From 2012 to 2018, the total amount of nighttime light in all prefecture-level cities in the Guangdong-Hongkong-Macao region showed an increasing trend. The total amount of night light in Guangzhou has always been highest, with Shenzhen, Dongguan, Foshan and other economically developed cities maintaining steady increases. The growth rate of nighttime light in small and medium-sized cities was significantly higher than in large cities, and was as high as 310.35% in Shanwei City. Small and medium-sized cities located in the surrounding areas show great development potential. 2) In the rank-size distribution analysis, from 2012 to 2018, the q value at prefecture level and county level decreased by 16.86% and 13.52% respectively. At the prefecture and city level, the distribution of urban scale has gradually changed from a first-place distribution to a rank-size distribution. At the district and county level, it has remained a first-place distribution, but the tendency to disperse has been greater than the tendency to concentrate. The "Core-Edge" urban network structure that had prevailed in the Guangdong-Hongkong-Macao region for a long time has gradually been broken. The gaps between urban structure levels are gradually narrowing, and the scale development is gradually becoming more balanced across the whole region. 3) It can be seen from the analysis of the Nighttime Light Development Index that the differences in nighttime light levels and population distribution levels in the Guangdong-Hongkong-Macao region are gradually decreasing, with the imbalance between cities showing a decreasing trend year by year. The rate of decrease of NLDI in small and medium-sized cities is faster than in large cities, which indicates that the development of small and medium-sized cities is faster. The NLDI values of Jieyang City, Shanwei City and Shantou City, which are all in the east of the Guangdong-Hongkong-Macao region, decreased most significantly, indicating that the east of the region has shown a strong development trend in recent years. This paper presents an analysis the evolution of urban scale distribution in the Guangdong-Hongkong-Macao region from the perspective of spatial statistics, and its dynamic urban development in recent years is discussed herein. These findings have both theoretical and practical significance for optimizing development as well as for scientifically informed distribution of resources in the region.

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    Characteristics of the Jobs-Housing Balance in Central Guangzhou Based on Open Big Data
    Lin Xunyuan, Wang Guangxing, Hu Yueming
    Tropical Geography    2020, 40 (2): 254-265.   doi: 10.13284/j.cnki.rddl.003218
    Abstract258)   HTML6)    PDF (8797KB)(55)      

    This paper comprehensively analyzes the spatial distribution relationship between employment and residence in central Guangzhou on a meso level with the help of the Baidu Thermal Map, Baidu Real-time Road Conditions, and Baidu POI data. The results show that: 1) high-value areas where the population gathers during working hours are decently marked with plaques, but most of these are concentrated in the core area. The population is primarily concentrated around the commercial areas and transportation lines of various districts because of the close connection between employment activities and transportation. Examining the main functions of specific areas revealed that they are dominated by employment centers, business centers, and transportation hubs with a strong orientation towards work. High-value leisurely areas are relatively concentrated, have higher land use efficiency, and show a polycentric circle structure. The population is principally concentrated in the traditional local and newly developed commercial residential areas, which are relatively staggered from the core business district. There is a distinct difference between the working areas and places of gathering during non-work hours. The high-value places of gathering during non-work hours are mostly residential land; 2) from the correlation between the degree of population aggregation and the density of POI facilities, the density of POI facilities is more significant in areas with higher population aggregation, during both the work and non-work hours. Therefore, population aggregation has certain selectivity and is primarily concentrated in the area where urban infrastructure development is relatively complete; 3) according to Jobs-housing balance index measurements at the meso level, the ratio of occupation and housing (indicates the relative balance of occupation and housing) of each block in central Guangzhou is between 0.73 and 1.54 with little difference between regions. From a distribution perspective, the blocks with higher scores are mostly distributed in the core area (primarily concentrated in the Yuexiu District, northern Liwan District, and southern Tianhe District) and the blocks with lower scores are mostly distributed in the peripheral or marginal zones of the core area (primarily scattered in the Haizhu, Liwan, and Baiyun Districts); 4) from the perspective of the city’s response to traffic, peak morning congestion in central Guangzhou is greater than peak evening traffic. However, the overall variation in road conditions is minimal, and there is no particularly serious commuting phenomenon in the area.

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    Diffusion Characteristics of the Corona Virus Disease 2019 (COVID-19) Outbreak in Guangdong Province
    Liu Yi, Li Yuan, Li Zhuoling, Han Fangfei
    Tropical Geography    2020, 40 (3): 367-374.   doi: 10.13284/j.cnki.rddl.003217
    Abstract246)   HTML15)    PDF (2497KB)(141)      

    This report analyzes the spatiotemporal spread characteristics and the spatial variation of the coronavirus epidemic based on detailed information of confirmed COVID-19 cases released by the city health commissions in Guangdong Province. The report finds that: 1) the confirmed cases in Guangdong Province maintain certain age distribution characteristics. Middle-aged people represented the largest number of cases, followed by young people, and lastly, the elderly. These results are similar to national statistics; 2) the epidemic spread ratio in Guangdong is 0.198, which indicates that the anti-epidemic measures in Guangdong have effectively suppressed the spread of the epidemic; 3) the difference between the epidemic spread pattern and comprehensive risk pattern in Guangdong Province is significant. Medium-sized cities (third and fourth tier) have higher diffusion risk and medium comprehensive risk. Developed cities have lower diffusion risk but higher comprehensive risks, whereas undeveloped areas in eastern and western Guangdong are safer. Medium-sized cities are apparently weak areas that can be easily overlooked in anti-epidemic work; therefore the control of such areas should be strengthened; 4) the results of Guangdong's epidemic prevention measures can be actively promoted in the future to reduce public anxiety. The current priority should be the prevention of a second epidemic shock caused by returning workers and school students. In the middle-late stages of epidemic prevention, the implementation of risk management should be differentiated according to the epidemic risk levels among different cities for the sake of restoring social production and avoiding the negative impacts towards society stemming from the over use of anti-epidemic measures, especially for vulnerable and underdeveloped areas.

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    Spatial-Temporal Distribution and Influence Mechanism of Internet Public Attention on COVID-19: A Case Study on the Baidu Searching Index
    Sun Yuting, Xiao Fan, Zhou Yong, Tian Guangzeng
    Tropical Geography    2020, 40 (3): 375-385.   doi: 10.13284/j.cnki.rddl.003244
    Abstract235)   HTML7)    PDF (1613KB)(90)      

    The rapid spatial spread of the Corona Virus Disease (COVID-19) in China during the Spring Festival has seriously endangered human health and garnered tremendous public attention via the Internet and social media. Although public attention plays a critical role in risk surveillance and epidemic prevention, there is a lack of comprehensive discussion related to its spatial-temporal differences and influence mechanism. This study focused on Internet public attention on COVID-19 using spatial analysis, spatial-temporal visualization, regression analysis of panel data, and other methods to investigate provincial spatial-temporal differences and possible influence factors of public attention in China from January 9 to March 2, 2020. In terms of data collection, the Baidu Index (BDI) was used as the measurement of public attention, disease-related data were recorded from the National Health Commission of PRC, and the population movement of Wuhan was based on geographic services of Baidu Qianxi. As per the findings 1) The spatial distribution pattern of public attention can be described as “large differences between east and west regions, higher in coastal areas than inland areas, and consistent with the areas of epidemic distribution.” In terms of temporal characteristics, there was a significant increase in the daily average of public attention in all provinces after the “Wuhan Lockdown,” and the same distribution pattern of overall levels of public attention was observed before and after the “Wuhan Lockdown.” Public attention reached its peak during the Spring festival and subsequently experienced a fluctuating decline with the periodic routine (incubation-outbreak) of the development of the epidemic. The themes of public attention moved from “searching information on related viruses in the early stage”, to “focusing on clinical diagnosis” and “the recent status of the development of the epidemic.” 2) Public attention is influenced by daily dynamic levels, including disease factor and population movement related to Wuhan, and economic/social development levels with fixed regional features. 3) Different phases of the issue—attention cycle receive different levels of attention. The effect of influence mechanisms on public attention before and after the virus outbreak is significantly different. Prior to the outbreak, information disease-related factors of confirmed cases and deaths could increase the public’s awareness and satisfy their fact exploration. After the outbreak, public attention was focused on population outflows from Wuhan. Compared to the first stage, the effect of regional factors on public attention increased after the outbreak, indicating that as the epidemic becomes gradually controlled, regional factor may have a sustainable and stable impact on public attention. 4) Media technology indirectly affects the public’s searching behavior during the epidemic. Higher amounts of available online information correspond to less searching behavior as the public becomes more informed. 5) The announcement of the “Wuhan Lockdown” did not cause a massive population movement as compared to the travel rush (Chunyun) during the Spring Festival. This indicates that the role of the incubation period may have had a negative impact of population movement on public attention before the epidemic outbreak, and that the media agenda and intervention from state authorities could arouse public attention on population outflow from Wuhan after the outbreak. Based on the findings, it is suggested that the government should focus on public searching volumes and enforce timely measures to surpass the speed of epidemic spread.

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    Accuracy Comparison of Four Gridded Population Datasets in Guangdong Province, China
    Lin Danchun, Tan Min, Liu Kai, Liu Lin, Zhu Yuanhui
    Tropical Geography    2020, 40 (2): 346-356.   doi: 10.13284/j.cnki.rddl.003220
    Abstract223)   HTML6)    PDF (2198KB)(60)      

    The spatial distribution of population is foundational information for policy making, disaster prevention, economic development, environmental protection, and natural sciences or socioeconomic research. Analyzing different gridded population products is essential for learning their characteristics and proper application. Considering timeliness of data and convenience of access, this study compared the spatial consistency of WorldPop, GPW v4 (Gridded Population of World, version 4) and two types of Gridded Population of China datasets in Guangdong Province, China, a province with significant population density differences. The sixth census data in 2010 were divided into high, middle, and low density groups and used as reference data to validate these four datasets on numerical and spatial distribution of error. Moreover, the study used average absolute error, average relative error, root mean square error, correlation coefficient, four indicators, ratio error statistics, and the Taylor diagram for quantitative evaluation. Then, the spatial distribution of the ratio error and the accuracy of the four datasets in different population density regions were analyzed. Finally, an evaluation of error sources and applications from two aspects, including methods for spatializing census data and variables selection of spatial model, was performed. The findings of the study are as follows: 1) These four population datasets have similar spatial distribution trends, and the population is concentrated in the Pearl River Delta regions such as Guangzhou, Shenzhen, Dongguan, Foshan, Zhongshan and Chaoshan regions such as Shantou and Jieyang. The WorldPop dataset had the highest relative accuracy in the whole Guangdong Province, as well as in the high population density area, whereas the GPW v4 dataset performed better than WorldPop in the middle and low population density areas; however, GPW v4 had a shortcoming in depicting population distribution beneath the township level because of the areal-weighting method used. The two types of Gridded Population of China datasets had relatively lower accuracy than the other two datasets. 2) The accuracy of the four population datasets in Guangdong Province was limited mainly by the spatial method based on the regression algorithm, the weighting method, the selection of model variables, and also related to the geographical and social environment of Guangdong Province. 3) The WorldPop dataset is suitable for detailed research in areas with medium and high population density, GPW v4 is suitable for long-time, minimal research units larger than townships, and the first type of Gridded Population of China dataset is suitable for study that requires consideration of the distribution and spatial heterogeneity of population beneath the township level. The second type of Gridded Population of China dataset is suitable for long-time study that requires consideration of the details of the population distribution and changes of spatial pattern. This study provides important basic information for research and applications using gridded population datasets.

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    Spatio-Temporal Evolution and Risk Profiling of the COVID-19 Epidemic in Shaanxi Province
    Wang Jiaobei, Li Gang, Wang Jianpo, Qiang Jingqi, Zhu Dandan
    Tropical Geography    2020, 40 (3): 432-445.   doi: 10.13284/j.cnki.rddl.003246
    Abstract214)   HTML5)    PDF (3501KB)(104)      

    The sudden outbreak and spread of the Corona Virus Disease 2019 (COVID-19) has posed great challenges to the society as well as the academia of not only China but the whole world. The occurrence of epidemic has obvious time and space attributes. Analysis of the spatiotemporal diffusion pattern and process of the epidemic reflects the dynamics of the interaction between humans and the COVID-19, it is worth discussing from the perspective of geography, which is very important for measures for prevention and control of this public health emergency. Based on the confirmed COVID-19 cases’ details manually extracted from the official reports and the relevant Point Of Interest (POI) data, this study aims to reveal the spatiotemporal evolution and risk profiling of the COVID-19 epidemic in Shaanxi province. The results are as follows: Firstly, the age-gender structure of the confirmed cases was diamond-shaped, where more males than females are confirmed, and the overall age trended to be medium-old aged, especially the age group of 40-49. Both non-local and local infections were dominantly caused by the flows of people between cities. Most of the infections belonged to small clusters of core families due to imported cases from Wuhan City, while other large mixed cluster infections in special places may have a deep influence. Secondly, the epidemic evolution process can be roughly divided into three stages, namely wave development stage (Jan.23rd-Feb.6th, 2020), low-speed recession stage (Feb.7th-20th), and stable clearance stage (Feb.21st-Mar.15th). There were lag periods between the cases’ confirmed dates and the onset or initial diagnosis dates. Moreover, the initial reporting dates of confirmed populations were synchronized with the overall evolution of the epidemic. Thirdly, the spatial flow of the epidemic to Shaanxi province was different from that to other provinces around Hubei. That is, it had a unique spatial pattern of only a single cluster center. The overall spatial distribution of the epidemic presented an inverted T-type pattern concentrated in central and southern Shaanxi with significant spatial differentiation. The spatial evolution at the city level was three-pronged. Here, the Wuhan-Xi'an path was the most frequent flow path, exhibiting the flow pattern of "from one source to many sinks, and from Wuhan to central and southern Shaanxi". Finally, the high risk areas were these key cities, for example Xi'an, as shown by the "one big cluster with three small collections" pattern, with the risk level in urban areas being higher than that in the surrounding counties.

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    Spatio-Temporal Variation of Drought in Guangdong Province from 1960 to 2014
    Wang Shuihan, Qiu Jianxiu, Wang Dagang
    Tropical Geography    2020, 40 (2): 357-366.   doi: 10.13284/j.cnki.rddl.003236
    Abstract206)   HTML6)    PDF (17635KB)(68)      

    Drought has a serious impact on socio-economic development in China and around the world. This study used daily precipitation records from 24 meteorological stations in Guangdong Province, China from 1960 to 2014 to analyze the spatio-temporal characteristics of drought in that region based on the Equivalent Dry Period (EDP) metric converted from the Average Waiting Time for Precipitation index. Particular emphasis was placed on the spatio-temporal evolution of drought in the 21 stcentury. The results showed that the EDP index was suitable for analyzing drought characteristics in Guangdong Province. Overall, drought intensity decreased from east to west and from south to north, with coastal areas experiencing more severe drought than northern and western areas. During the study period, decadal variations and an annual increasing trend in EDP were obvious over the entire province. In addition, seasonal drought was prominent, occurring most frequently in autumn and winter, followed by spring; the drought’s central location varied from season to season. Drought frequency, intensity, and spatial extent were all higher in the early 21 stcentury than those in the late 20 th century. Specifically, since the turn of the century, both Dongyuan Station in the eastern Pearl River Delta and Luoding Station in western Guangdong showed significant increases in EDP and emerged as new drought hotspots. From a seasonal perspective, autumn and winter drought intensified most severely and tended to extend throughout Guangdong Province, with an EDP increase of 23% from the late 20th century to the early 21 st century. Spring drought worsened more gradually and summer drought occurred more frequently (though still rarely) in the early 21 stcentury. These results identified the spatial pattern and temporal evolution of drought in Guangdong Province since the turn of the century and provide scientific references and technical support for drought monitoring and mitigation in southeastern China.

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    Estimating Inland Water Depth Based on Remote Sensing and Machine Learning Technique
    Wen Kaixiang, Li Yong, Wang Hua, Yang Ji, Jing Wenlong, Yang Chuanxun
    Tropical Geography    2020, 40 (2): 314-322.   doi: 10.13284/j.cnki.rddl.003237
    Abstract203)   HTML12)    PDF (6493KB)(42)      

    This study investigates the application of three machine learning algorithms, e.g. the Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM) algorithms, in water depth estimation using Sentinel-2 multispectral satellite images. A case study is conducted in the Meizhou Reservoir in Guangdong, China, and a comparative analysis of the inversion results is performed. The results are validated against in-situ measured data using an unmanned ship, in which a global positioning system and a single wave velocity sounding system are integrated. The experimental results based on our water depth inversion models demonstrate good inversion accuracy and efficiency of the machine learning water depth inversion model constructed using 7 925 water depth data samples and satellite multispectral images. By adjusting the key parameters of each model such that the model reaches the optimal state, the determination coefficient (R 2), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Bias were used to evaluate the accuracy of the models. For water depth inversion, the RF model indicated that R 2 = 0.80, RMSE = 2.21, MAE = 1.51, and Bias = 0.00; the XGBoost model indicated that R 2 = 0.79, RMSE = 2.22, MAE = 1.50, and Bias = -0.01; and the SVM model indicated that R 2 = 0.78, RMSE = 2.23, MAE = 1.60, and Bias = 0.01. To determine the efficiency of each model, the models’ running times were obtained: 3.92 s for RF, 4.26 s for XGBoost, and 6.66 s for SVM. Notably, the RF model is superior to the XGBoost and SVM models in terms of inversion accuracy and efficiency. Moreover, the advantages and disadvantages of each model can be inferred from the prediction result graph. The prediction results of the RF model are more detailed, and the terrain is clearer compared with those of the XGBoost model. The SVM model does not achieve ideal prediction using the same dataset, and the error at a shallow water depth is much worse than those of the other two models. The scatter plots indicate that the inversion deviation is not obvious between the RF and XGBoost models, and the prediction results are more consistent with the actual results. However, the scatter plot of the SVM has a horizontal bar near 11 m; therefore, it predicts the water depth value in this interval incorrectly. Furthermore, the errors of the RF and XGBoost models evaluated by the standard evaluation method are lower than that of the SVM model, indicating that those models have a higher prediction accuracy for water depth inversion. In summary, the machine learning models for water depth estimation yielded good performances in this study, and they are suitable for estimating the water depth using remote sensing images with lower economy and time cost, especially in unreachable waters.

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    Development and Accuracy Assessment of a Hyperspectral Data-Based Model for Leaf Nutrient Content Extraction in Wetland Tree Species
    Li Dan, Huang Yuhui, Sun Zhongyu, Zhang Weiqiang, Gan Xianhua, Wang Zuolin, Sun Hongbin, Yang Long
    Tropical Geography    2020, 40 (2): 175-183.   doi: 10.13284/j.cnki.rddl.003241
    Abstract190)   HTML16)    PDF (1219KB)(58)      

    Plant nutrient status is a comprehensive response to soil nutrient supply, crop nutrient demand, and crop nutrient abilities. Detecting variations in plant nutrient content is an important aspect of forest management. However, conventional chemical analysis techniques are often time and labor intensive, particularly when applied over large areas. In recent years, some convenient and non-destructive tools have been applied to monitor plant biochemical properties; however, there is no agreement about which methods are most reliable. Among the available methods, some employ hyperspectral data to nondestructively estimate levels of nitrogen, phosphorus, and potassium in plants, thus providing a theoretical framework to support scientific forest management. Certain optical characteristics in the visible and near-infrared regions are closely associated with the absorption features of chlorophyll, other pigments, water, and chemicals in leaves and canopies. However, the efficacy of utilizing spectral data to detect various nutrient parameters is dependent on the data processing methods employed. In this study, we applied near-infrared spectroscopy to examine the leaves of nineteen wetland forest species and assessed various models’ performances in estimating Total Nitrogen (TN), Total Phosphorus (TP) and Total Potassium (TK) content in the vegetation. Eleven spectral preprocessing methods and three spectral data dimensionality reduction methods were used to preprocess the spectra. And two of algorithms, the Partial Least Squares Regression (PLSR) and Support Vector Machine Regression (SVR), were used to develop the nutrients prediction models. The determination coefficients (R 2) and Root Mean Square Error (RMSE) of the models were used to evaluate the performance of the models for calibration, cross validation and prediction datasets. The Relative Percent Difference (RPD) for the prediction dataset was also used to assess the models. Results showed that the Standard Normal Variate (SNV) approach combined with the first derivative (1 st) preprocessing method had the highest accuracy among the 11 data pretreatment approaches, with RPD values of 2.35, 2.39, and 2.45 for TN, TP, and TK, respectively. Among the different dimensional-reduction methods, the Principal Component Analysis (PCA) performed the best, and SVR outperformed PLSR in parameter estimation. Models incorporating the SVR algorithm and data preprocessed using the SNV+1 st approach yielded the best prediction results for the three parameters. The best model for TN had ${R^{2}}_{p}$, RMSEp, and RPD values of 0.85, 2.82% and 2.50, respectively; best model for TP had ${R^{2}}_{p}$, RMSEp, and RPD values of 0.90, 0.55%, and 2.83, respectively; and best model for TK had ${R^{2}}_{p}$, RMSEp, and RFD values of 0.85, 3.80%, and 2.60, respectively. The results indicated that visible and near-infrared spectra can be used to estimate the leaf TN, TP, and TK content of wetland trees. However, before model calibration, the proper preprocessing of the spectral data is necessary to improve the performance of the models.

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    Rural Spatial Restructuring: Theoretical Research Progress and Framework Construction
    Lixia Jin, Zhimin Wen, Jianhong Fan, Zhiwei Du
    Tropical Geography    2020, 40 (5): 765-774.   doi: 10.13284/j.cnki.rddl.003278
    Abstract189)   HTML11)    PDF (1365KB)(92)      

    Against the background of urban-rural integration and the increasingly complex human-land relationship in rural areas, rural spatial restructuring has emerged as an important subject in rural geography. This article preliminarily defines the connotation of rural spatial restructuring. It examines and reviews the theoretical research progress in the field of western post-productionism, domestic rural territorial system, and political economy. In addition, the article also constructs a multi-perspective, multi-element, multi-theoretical framework of rural spatial restructuring. The research shows that first, in the context of western "post-productivism," as the study of the rural spatial restructuring begins to demonstrate the consumption, social-cultural and post-modern turns, the research on multi-function, global rural transformation, and spatial reconstructing becomes the focus area. Second, based on the territorial system of human-environment interaction of rural geography, domestic research emphasizes the process-mechanism-regulation of rural spatial reconstructing and farmers' economic spatial behavior from the micro perspective. Third, accompanied by land capitalization and the increasing importance of rural labor mobility, rural spatial reconstructing presents the Chinese characteristics of top-down political and economic transformation and focuses on the space-power relationship between rural collective organizations and other subjects, such as governments, enterprises, individuals, etc. This has become an important perspective of rural spatial reconstructing. Fourth, the political and economic geography and "social-spatial" dual dialectics provide good research paradigms and methods. Moreover, the theoretical study of rural space reconstructing should systematically integrate political and economic theories (spatial production, subject initiative, land capitalization, social relation network, the territorial system of human-land interaction, and peasant household geography) and strengthen the studies on multi-factor interactions and their spatial response mechanisms (nature, economy, society, and culture). To achieve this, the formation and evolution of rural spatial pattern with multi elements and multi dimensions, rural social spatial reproduction, rural labor spatial production from the perspective of initiative, government policy system, and finally, the innovation of urban and rural spatial governance system should be emphasized.

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    A Research Framework for the Application of Volunteered Geographic Information in Post-Disaster Recovery Monitoring
    Yan Yingwei, Ma Dawei, Fan Hongchao
    Tropical Geography    2020, 40 (2): 184-193.   doi: 10.13284/j.cnki.rddl.003239
    Abstract183)   HTML8)    PDF (2297KB)(82)      

    In recent years, many studies on the application of Volunteered Geographic Information (VGI) to natural disaster management have been reported. To date, it has been shown that VGI can provide big geospatial data, incorporating rich content and extensive spatiotemporal coverage, in a real-time and cost-effective manner. Thus, it can facilitate disaster management by filling information voids known to occur in traditional geospatial datasets. However, existing studies have mostly focused on disaster prevention, preparedness, and response phases, and few studies have focused on post-disaster recovery. The aim of the proposed work is to help bridge this research gap by investigating how VGI data can facilitate post-disaster recovery monitoring, both in general, and for specific aspects such as tourism, business, industry, and the daily routines of residents. In the work reported here, we first review the development of VGI research in the decade since 2007, and then propose a research framework for post-disaster recovery monitoring, based on VGI data. The research framework involves three key components—data acquisition, data quality control, and data mining. Data acquisition is generally referred to as VGI collection (for example, OpenStreetMap, Twitter, and Flickr data), while authoritative data (such as remote sensing data, official statistics, and field survey data) can be collected as ancillary information. Data quality control is based on a fuzzy expert system, which considers Linus’ law, metadata, data lineage and provenance, geographic contexts (Tobler’s first law of geography), user credibility, spatiotemporal data density, and user activeness, and leverages artificial neural networks (deep learning) for optimizing the fuzzy rule sets of the expert system. Data mining is based on the transformative paradigm, using a combination of quantitative and qualitative approaches, involving text mining, spatial statistics, and machine learning. Using this combination, the status of infrastructure (roads, electricity, water, transport, housing, buildings, and telecoms), the economy (external sources of economy, internal sources of economy, and services), and safety (reputation, secondary disasters, health, security, and stability), which are the three main measures of post-disaster recovery, are investigated. This work thus paves a way for future studies related to this topic, identifying both research and practical implications. We also identify limitations in using VGI for post-disaster recovery management. The first of these is that a VGI source may rapidly become obsolete due to the fast development of cyberspace, making it imperative for researchers to keep the technique up-to-date, adapting it to the diverse and emerging VGI sources. The second limitation is that certain VGI platforms do not provide all the data available in their databases, and have imposed constraints on their Application Programing Interfaces (APIs). The third limitation is related to privacy issues pertinent to VGI data use. We suggest that the future work should also focus on seamlessly integrating VGI with traditional post-disaster recovery monitoring approaches, such as remote sensing, field surveys, and resident interviews.

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    Extraction and Analysis of Cultivated Land Experiencing Rocky Desertification in Karst Mountain Areas Based on Remote Sensing—A Case Study of Beipanjiang Town and Huajiang Town in Guizhou Province
    Zhao Xin, Zhou Zhongfa, Wang Lingyu, Luo Jiancheng, Sun Yingwei, Liu Wei, Wu Tianjun
    Tropical Geography    2020, 40 (2): 289-302.   doi: 10.13284/j.cnki.rddl.003233
    Abstract181)   HTML10)    PDF (80040KB)(55)      

    Determining the accurate distribution of cultivated land is a prerequisite and foundation for the development of precise, modernized agricultural practices, and it is an important factor in land policies and agricultural production at the local scale. However, in karst areas, because of the complex terrain and cloudy and rainy weather conditions, the images often show repeated patterns of “identical foreign matter”; i.e., it is difficult to obtain accurate farmland information using traditional image-based farmland extraction. To solve this problem, Beipanjiang Town and Huajiang Town in Guizhou Province were selected as target areas in this study. Using Google’s high-resolution remote sensing images and combining the concepts of zoning and grading, accurate extraction and evaluation of cultivated land in the study area could be performed based on deep learning methods and traditional constraints. Firstly, based on visual data, farmland was divided into three types: farmland in gentle slopes), Relatively slender and unevenly distributed farmland, and farmland with blurred edges. Then, the Holistically-Nested Edge Detection (HED) model, Richer Convolutional Features (RCF) network model, and D_LinkNet semantic segmentation model were used to extract cultivated land. After confirming that the prediction data were sufficiently accurate, cultivated land was further classified based on the slope and topographical data of the test area, and the distribution characteristics of cultivated land within various terrains were studied. The results showed that: 1) The area of cultivated land in the study area classified via visual morphological differences and various models was 9 867 ha, which is basically consistent with the actual area. The F-measure was mainly distributed between [0.82, 0.98] and was affected by the topography and the exposure rate of rocks. The precision of arable land extraction in areas with severe rocky desertification was low. 2) In terms of morphological accuracy, the Generalized Intersection Over Union (GIOU) of the predicted and actual area of cultivated land was mainly distributed between [0.7, 1], The correct segmentation rate was more than 85%, which indicates that the predicted farmland boundaries generally coincided with the actual plot boundaries, and the extraction results reflected the actual situation in the study area. The research area mainly consists of karst cultivated land, which accounted for 74% of the total arable land area in the study area. Further, the degree of rocky desertification is relatively serious, of which light and moderate rocky desertified arable land accounts for about 32% of the total cultivated land. The narrowness and fragmentation of cultivated land in rocky desertified areas are greatly affected by anthropogenic activities. Land closer to residential areas is more accessible, and the tendency of the plots to be fragmented increases as the land utilization rate increases. In summary, the method proposed in this study can effectively extract cultivated land in areas with fragmented cultivated land and complex terrain, thus providing accurate data to support regional development, cultivated land management and research, and environmental protection and decision-making.

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    The Bibliometric Analysis on the 40th Anniversary of Tropical Geography Based on CiteSpace
    Kai Liu, Minying Lu, Xiaoling Li
    Tropical Geography    2020, 40 (6): 957-969.   doi: 10.13284/j.cnki.rddl.003285
    Abstract177)   HTML14)    PDF (3067KB)(108)      

    On the 40th anniversary of Tropical Geography, a Bibliometric analysis based on CiteSpace was made on 2 938 articles published in tropical geography during1980-2019. At the interval of every 10 years, this paper conducted keyword co-occurrence analysis, keyword emergent detection, author co-occurrence analysis and institution co-occurrence analysis, aiming to explore the trends of the themes, historical burst terms, the core author partnerships and the core institutions partnerships in Tropical Geography. As a result, in the first 20 years, the research topics and areas of Tropical Geography were concentrated, mostly focusing on south China and the development and utilization of its resources. The cooperation among the core authors was weak and overall dispersed. Besides, it mainly reported the research results of Guangzhou institute of Geography and the cooperation among the core institutions was less. Since 2000, the number of research themes has increased significantly and has formed diversified research hotspots. The research area has been expanded, but it is still concentrated in southern China. More cooperative teams were formed among the core authors, and the inter-team cooperation and communication were significantly enhanced. The proportion of research results of universities and other institutes has increased greatly, and cooperation between institutions has been strengthened also.

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    Calculation of the System Delay Elasticity of the Beijing-Guangzhou Air Corridor with Analysis of the Air Flow Operation Structure
    Zhang Yinuo, Lu Zi, Ding Jianghui
    Tropical Geography    2020, 40 (2): 194-205.   doi: 10.13284/j.cnki.rddl.003219
    Abstract174)   HTML6)    PDF (11563KB)(27)      

    During the last 10 years, aviation demand in China grew faster than transport capacity, leading to the intensification of the conflict between airspace capacity and flight flow and causing significant route congestion and flight delays. The Beijing-Guangzhou air corridor is considered the core component of the “inverted N-shaped north-south frame” of China’s air corridor pattern. In this study, a multi-level measurement framework that includes delay, duration-delay and accumulation-delay elasticity coefficient was constructed. By applying the actual track point data of 848 flights during a 24 h period in the Beijing-Guangzhou air corridor, the duration of the delay of a single flight, the system delay accumulation, and the system delay elasticity coefficient were calculated. The delay elasticity of the Beijing-Guangzhou air corridor system was evaluated, and its relationship with the air flow structure was analyzed. The improvement of the node-link settings and grid division reflected the characteristics of fine-grained research and the reasons for the heterogeneity of the delay elasticity were analyzed based on the airline network structure. The research suggests that: 1) overall, the flights in this air corridor primarily generate delay and show delay absorption capacity in low traffic periods. The average delay time for flights is 1.4 min. The mean delay of departure flights is generally higher than that of arrival flights. With the increase of flow intensity between hub airports, the mean and peak amplitudes of flight delay increase. According to the standard statistics of delay duration >15 min, the probability density and mean delay of each confluent flight are higher than those of a direct flight between the hub airports; 2) the delay of the Beijing-Guangzhou air corridor system presents a dynamic process that accumulates in the central route while peripheral routes recover. The accumulated delay of central airlines is 689 min, while the recovery of peripheral airlines is 936 min. The preference of the operators for central routes makes high-density traffic convergence the principal cause of delay accumulation; 3) the delay elasticity of the Beijing-Guangzhou air corridor system varies greatly among different air route segments and improves significantly with an increase in the number of paths and the dispersion of traffic flow between nodes. Multi-link air route segments trigger active delay absorption and thus have a strong delay recovery ability. The relationship between the delay elasticity and the air flow operation structure of the air corridor system is established by three key elements: the central route, the peripheral route, and the track clusters. This article provides a new perspective for the measurement and understanding of system delay elasticity and a basis for the selection of diverse routes and flight schedules in air corridors. Contrary to the previous elastic strategy of adjusting the allocation of flight slot resources and retaining the remaining capacity, this study reflects that flexible airspace utilization and dynamic airspace management, namely, adaptive route reconstruction and optimization of connections, would improve the efficiency of the system elasticity guarantee system.

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    Spatial Heterogeneity in Chinese Urban Innovation Capabilities and Its Determinants: Approach Based on the Geographically Weighted Regression Model
    Chen Yiman, Li Lixun, Fu Tianlan
    Tropical Geography    2020, 40 (2): 323-334.   doi: 10.13284/j.cnki.rddl.003210
    Abstract172)   HTML6)    PDF (17451KB)(47)      

    Innovation is the primary driving force of development and provides strategic support for building a modern economic system. Its role in promoting regional development has been studied and acknowledged by academics. Since the Chinese economic reform, the country’s scientific and technological level and capacity for innovation has significantly improved, and the overall national strength has steadily increased. Presently, innovation plays a critical role in China's economic transformation from a stage of high-speed growth to a stage of high-quality development. Based on urban invention patents, this study analyzes the spatial characteristics of the innovation capabilities of Chinese cities by using the kriging interpolation method and a spatial autocorrelation model. The Geographical Weighted Regression (GWR) model was used to explore the spatial heterogeneity in the factors influencing the innovation ability of 289 cities, and to reveal the spatial differences in the dominant factors. The results indicate that the innovation ability of Chinese cities shows a decreasing trend from the southeast to the west, and the cities with the highest innovation capacity are concentrated in the southeastern coastal areas. The cities in the west, mainly in Tibet, have the lowest innovation capacity. The spatial agglomeration is significant. In terms of the determinants, the significance level of each variable was good. The proportion of significant regions in all cities in order from large to small is financial input, talent element, economic foundation,economy extraversion, financial environment, and information level. In addition to the significant positive correlation between financial input and urban innovation capacity, there are positive and negative correlations among the other determinants. Moreover, the range of the index’s regression coefficient is large and has an obvious spatial differentiation. The talent element is positively correlated with the innovation ability of most cities. The influence of the economic foundation and information level on urban innovation ability is positive for economically developed areas and negative for underdeveloped areas. Economic extraversion is positively correlated with the innovation ability of the eastern coastal areas and the central and western regions, but negatively correlated with that of most cities in northeast and north China. The financial environment, represented by residents' savings, has a positive correlation effect on the innovation output of the northeast and western regions, while it has the opposite effect in the Yangtze river delta and other regions. The input of innovation elements in China is still a leading determinant in improving the country’s innovation ability. For southeastern Chinese cities with a higher level of economic development, more attention should be paid to improving their economic level and promoting the overall improvement of their innovation ability. For cities in the northeast and west, where the economic level is relatively inferior, financial support plays a significant role in the development of their innovation activities. Thus, attention should be paid to the cultivation of the financial market in these areas. The research shows that there are spatial differences in the factors influencing urban innovation capabilities in China, and the characteristics of different cities should be taken into account when formulating innovation policies to make policies more targeted and facilitate the healthy and coordinated development of national urban innovation.

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    Diel Variations of Hydrochemistry and Influencing Factors in the Surface Water of the Yelanghu Reservoir in Puding, Guizhou Province
    Wang Jialu, Ren Juan, Wang Yong, Li Weijie, Lou Zhao, Chen Jia
    Tropical Geography    2020, 40 (2): 335-345.   doi: 10.13284/j.cnki.rddl.003214
    Abstract172)   HTML6)    PDF (2742KB)(25)      

    A karst reservoir is a type of semi-natural and semi-artificial water body. Owing to the dual regulation of fragile geological background of the karst and human activities, the geochemical indexes of karst water body differ considerably. To understand the variation processes of hydrochemistry of the Yelanghu karst reservoirs, which are located in Puding in Guizhou Province, the diel cycles of geochemistry of their surface water were measured for three days and nights. The results indicate that: 1) the ion indices of the reservoir water did not exhibit obvious diel variations due to variable weather and hydrological conditions, whereas regular indices of water temperature, Dissolved Oxygen (DO), pH, and partial pressure of CO2 exhibited apparent diurnal fluctuations. Under the control of water-rock interactions and the effect of the coal-bearing bedrock, the water chemical type of the Yelanghu Reservoir is Ca-HCO3·SO4. 2) By calculating the thermodynamic parameters and analyzing the principal components, it is found that these parameters are controlled by temperature, biological effects, and human activities, as well as storage and discharge of the reservoir, of which their contribution rates are 21.66%, 17.28%, 14.08%, and 10.22%, respectively, indicating that the influencing factors of hydrochemistry of the reservoirs are multivariate. 3) During the study period, the variation ranges of the Yelanghu Reservoir water’s δD and δ 18O values were -60.61‰~-57.17‰ and -8.11‰~-8.85‰, respectively, and the mean values were -59.44‰ and -8.46‰, respectively. The δD and δ 18O values were smaller during the day and larger at night. During the day, the biological activity in the reservoir is primarily photosynthesis with weak respiration; whereas at night, it is primarily respiration, which consumes a large amount of O2 to obtain more light isotope 16O, thereby resulting in a decrease in DO concentration in the water at night and a negative 18O. However, a comparison of the d-excess value of the reservoir water with the local atmospheric precipitation shows that the d-excess value of the former (8.21‰) is significantly lower than that of the latter (9.64‰), indicating the main effect of unbalanced fractionation caused by evaporation over a long period of time.

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    The Residential Differentiation of Residents’ Overweight: A Case Study of Guangzhou
    Zhu Zhanqiang, Tao Xiaofang, Zhou Suhong
    Tropical Geography    2020, 40 (3): 487-497.   doi: 10.13284/j.cnki.rddl.003222
    Abstract172)   HTML4)    PDF (814KB)(32)      

    The rapid increase in the overweight rate among Chinese residents is accompanied by a complex overweight differentiation characteristic. However, little is known about the causes of the differentiation at a community level. Thirty years of housing system reform has led to China's housing pattern evolving into a variety of types. It will be of theoretical and practical value to study the mechanism of the influence of residential type on the rate of residents’ overweight under the specific policy and social background of China. Based on 962 questionnaires from 25 typical communities in Guangzhou (categorized into four residential types), we used chi-square analysis and a binary logistic regression model to analyze the residents’ overweight differentiation characteristic and its mechanism on a community level. The results showed that the overweight rate of residents and its differentiation characteristic varied between residential types. Demographic features and community environment were the core variables that explain the above-mentioned differentiation by residential type. 1) The incidence of overweight in the order of highest to lowest was as follows: historical district, indemnificatory housing, unit community, and commercial housing community. Commercial housing communities attract young people with high education, high income, a generally better health awareness and community resources availability leading to the lowest overweight rate. Due to long-term housing isolation, poor marketability and earlier construction, unit communities and historical districts drew residents with low education and income, in addition to which historical districts had a large proportion of the elderly. Consequently, both residential types had a higher overweight rate. Indemnificatory housing tended to support low-income groups, and usually had a poor community environment so although residents had a higher education level, there was less opportunity to use physical activity resources, therefore this residential type had a higher overweight rate. 2) Age and marital status were important influencing factors of overweight for all residential types which indicates that this is of concern for both the elderly and married population. With regard to other aspects of demographic and socioeconomic attributes, as well as leisure-time physical activity levels, overweight differentiation among the residential types had varied characteristics and mechanisms. An increase in income provided individuals with more access to social resources including physical activity facilities and food facilities, resulting in an overweight differentiation for both indemnificatory housing and unit communities. Moreover, in respect of indemnificatory housing, non-agricultural residents from other cities had higher income levels than other hukou types, so they tended toward higher physical activity and diet resource acquisition ability or a higher intensity physical activity (physical work) which reduced the overweight level. Education levels affected the leisure-time physical activities and other health behaviors of people in historical districts, leading to an overweight differentiation. Commercial housing communities consisted of higher income residents whose unhealthy work practices contributed to an overweight differentiation at the community level. This study revealed the characteristics and mechanism of overweight differentiation in Chinese residential patterns and proposes a number of community optimization measures to alleviate overweight, which may help improve the health of residents living in these communities and promote the implementation of the “healthy China” strategy. Further research might be needed to establish the mechanism of overweight differentiation in terms of gender and leisure-time physical activity.

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    Impact of Guinan Railway Construction on the Geomorphologic Value of the Libo-Huanjiang Karst World Heritage Site
    Xiong Kangning, Zhang Zhenzhen, Xiao Shizhen, Di Yongning, Xiao Hua, Zhang Ying, Zhang Yin, Liu Shuxi
    Tropical Geography    2020, 40 (3): 466-477.   doi: 10.13284/j.cnki.rddl.003225
    Abstract171)   HTML5)    PDF (4387KB)(40)      

    The relationship between protection of an outstanding universal value and regional development and utilization has always been an important aspect of World Heritage protection and management. As an important component of South China Karst, the Libo-Huanjiang karst World Heritage property was listed on the World Heritage list for its outstanding geomorphologic and aesthetic value, meaning that it should be protected by all the world. Its outcropped carbonate rocks developed in different geological ages and formed remarkable fengcong (cone karst) and fenglin (tower karst), which shows the change and evolution of landform between fengcong and fenglin. Guinan Railway, from Guiyang to Nanning in China, which will pass through the buffer zone of Libo-Huanjiang karst, is planning to be constructed for the display and community development of the world heritage property, as well as the poverty alleviation of the buffer zone (as peripheral coordination area of a world heritage property to reduce the adverse effects caused by human activities outside the area). The area of the property and its buffer zone are 366.47 km2 and 479.28 km2, respectively. This study used 3S technology and field studies to assess the impact of Guinan Railway construction on the hydrology, geology, and landforms of the area with regard to its geomorphologic value and the potential effects of the buffer zone. The results indicated that: 1) Carbonate rocks are continuously distributed throughout the property and its buffer zone; karst systems are obvious and support many springs. Underground rivers are mainly distributed in fengcong-valley, fenglin-valley, and depression landscapes. The area’s special hydrogeological conditions are represented by typical geomorphological types such as fengcong karst and fenglin karst as well as active groundwater features. 2) The Guinan Railway will pass through the buffer zone of the property, though not through the property itself, so will not directly influence its geomorphological value. The Chaoyang Tunnel will be located within the upper reach of the buffer zone, and the its capture rate of the Di’e River during construction is expected to be 0.88%. Although this is predicted to have little effect on groundwater flow diversion from the Di’e River, monitoring and management of the Chaoyang Tunnel will be indispensable. 3) The railway route is designed to cross the buffer zone via bridges, tunnels, and subgrades. All the bridges are designed to cross rivers without support piers, avoiding impacts to water quality and quantity. The Jiuwandashan No.2 Tunnel may reduce the groundwater level within its cone of depression, but would have little influence on the property’s hydrogeological conditions and karst processes. The exposed subgrades will cross non-karst landforms, having no effect on karst landforms within the property. 4) The hydrogeological units of the Da-xiaoqikong and Maolan-Huanjiang components, the two parts of Libo-Huanjiang karst, are different, with no unified groundwater hydraulic connection, so the Guinan Railway would not affect groundwater hydraulic connections and karst processes. 5) The railway route would affect 13 fengcong-depression sites with an area of 5.32 km2, accounting for 1.22% of the total area of the buffer zone. Therefore, it would have little influence on the zone’s buffering effect.6) The existence of the buffer zone protects the geomorphologic value of the property from potential impacts of Guinan Railway construction, as a buffer zone is meant to do. However, due to unique connections between changes in karst water environments and karst landform evolution, further research on the hydrogeological processes at karst-related natural World Heritage sites and the evolution of karst landforms is still needed. In addition, the monitoring and management of railway projects during the construction and operation periods should be strengthened.

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    Analysis of Spatio-Temporal PM2.5 Patterns Obtained Using Mobile Monitoring: Case Study Conducted in Central District of Guangzhou
    Song Jie, Zhou Suhong, Peng Yinong, Lin Rongping, Xu Jianbin
    Tropical Geography    2020, 40 (2): 229-242.   doi: 10.13284/j.cnki.rddl.003232
    Abstract160)   HTML7)    PDF (35229KB)(62)      

    It is crucial to address the global risk of disease caused by PM2.5 air pollution, which requires large-scale monitoring of PM2.5 pollution. Simulations of pollutant patterns are also necessary; however, it is currently difficult to accurately depict the spatial and temporal distribution patterns of PM2.5 pollution in cities using traditional air pollutant simulation methods. In this study, basic low-cost air quality monitoring equipment was used to conduct mobile monitoring of PM2.5 pollution in the central urban area of Guangzhou within the ring expressway, and 2,257,000 PM2.5 monitoring data were obtained at a frequency of 1 Hz. Using these data, simulation of PM2.5 pollution within the study area was conducted at a spatial and temporal resolution of 10 m × 10 m, and the reliability of collecting spatial and temporal patterns of PM2.5 pollution via the mobile device in the urban center was analyzed. The mobile monitoring data results showed the following: under stable weather conditions, there was a significant temporal correlation between PM2.5 data obtained under mobile monitoring and that from the fixed monitoring station (R 2: 0.72-0.86). The spatial and temporal distributions of PM2.5 pollution in the central area of Guangzhou showed significant spatial and temporal differentiations over short time periods. Temporally, the hourly average ranges in dry and wet seasons were 27 μg/m3 and 11 μg/m3, respectively, where the temporal periods of the highest and lowest concentrations occur depends were related to the background concentrations on the day. Spatially, there were higher values of PM2.5 near transportation hubs, commercial centers, industrial parks, and large commercial markets; however, lower values were found in parks, green areas, and high-end residential areas and on university campuses. Furthermore, spatial differentiation characteristics were evident, with values higher in the west and south and lower in the east and north during the dry season, but higher in the east and lower in the west during the wet season. Although there was no temporal correlation between high PM2.5 values during the day and peak traffic periods, pollution was spatially concentrated in the vicinity of important traffic nodes within the city, and the amount increased during peak traffic periods. These results show that the mobile monitoring method can be used to describe the spatial and temporal patterns of pollutants and key areas of exposure can be identified, which is of great significance for optimizing and adjusting the layout structure of monitoring sites and associated maintenance costs. Implementation of this method could enable the identification of high risk pollution routes, which would prevent and control pollution, improve the ecological environment, and enable targeted protection measures to be effectively evaluated. As such, use of mobile monitoring is important in the construction of smart cities and for realizing the long-term and high-precision air quality monitoring within cities under the support of smart geospatial technology.

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    Reconstruction of Shipwreck and Surrounding Relief at a Coral Reef in the South China Sea Based on Side Scan Sonar Image
    Liu Xiaoju, Shi Qi, Yang Hongqiang, Zhou Shengnan
    Tropical Geography    2020, 40 (2): 278-288.   doi: 10.13284/j.cnki.rddl.003221
    Abstract158)   HTML2)    PDF (13414KB)(42)      

    As sonic imaging instrument, side scan sonar is widely used in the qualitative detection and recognition of underwater landforms and objects. Some researchers have attempted to quantitatively reconstruct underwater landforms using the Shape From Shading (SFS) method, which is based on the principle of computer vision. At present, it is sometimes used in the investigation of coral reefs in China. In the present study, a quantitative reconstruction of shipwreck and its surrounding relief is carried out at a coral reef in the South China Sea based on single side scan sonar image. After the pre-processing steps of data format conversion, image generation, water removal, image gain and correction, and coordinate conversion, the side scan sonar image of the shipwreck area was used to retrieve the underwater topographic data. The study involved using an SFS algorithm based on minimization approach with the measured bathymetric data as the initial topographic condition to reconstruct the three-dimensional relief of the shipwreck and surrounding area. The mean absolute error was 0.77 m and the mean relative error between the retrieved and measured water depths was 4.5%, revealing the topographic and geomorphic features of the shipwreck area. The results show that the shipwreck area is located on the western side of the coral reef and has the typical geomorphologic form of a reef slope with water depth increasing from -1.8 m to -165.4 m from east to west. It can be divided into two relatively planar terraces and two steep slopes according to the water depth and slope gradient. The first terrace is approximately 46 m wide, with a mean depth of approximately -4.1 m and a mean gradient of approximately 1.4°; the first slope is approximately 35 m wide, with a mean depth of approximately -16.1 m and a mean gradient of approximately 28.8°. The second terrace is approximately 87 m wide, with a mean depth of approximately -26.7 m and a mean gradient of approximately 5.7°; the second slope is approximately 90 m wide, with a mean depth of approximately -63.3 m and a mean gradient of approximately 39.0°. The shipwreck is located on the second terrace of the reef slope. The shipwreck lies in EES-WWN orientation and is approximately 45 m long, 9 m wide, 4 m high, with a tonnage of approximately 500-600 tons. However, the shipwreck is no longer intact. The quantitative inversion and reconstruction of underwater landforms using side scan sonar images is an effective complement to the qualitative analysis of the images and can reveal the topographic and geomorphic characteristics of the coral reef in more comprehensive and detailed ways. In the future, the quantitative analysis method of side scan sonar imaging will have widespread applications in the investigation of topographic reconstructions, substrate types and coral community distributions, human activity footprint monitoring, and identification of special objects such as submerged reefs and shipwrecks.

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    Spatio-Temporal Characteristics and Transmission Path of COVID-19 Cluster Cases in Zhuhai
    Liu Zhengqian, Ye Yuyao, Zhang Hong’ou, Guo Hongxu, Yang Ji, Wang Changjian
    Tropical Geography    2020, 40 (3): 422-431.   doi: 10.13284/j.cnki.rddl.003228
    Abstract157)   HTML5)    PDF (1115KB)(82)      

    On the eve of the 2020 Spring Festival, an epidemic of COVID-19 broke out in Wuhan and spread quickly across the country through population movements, posing a serious threat to Zhuhai and other large cities. In this paper, epidemiological survey data for 98 cases of COVID-19 published by the Zhuhai Municipal Health Bureau were used to analyze the spatio-temporal characteristics of 26 epidemic clusters, conduct case analyses of four types of typical transmission routes, and determine the spatio-temporal patterns and transmission routes of the virusin Zhuhai, with three main results. 1) The epidemic’s spread in Zhuhai was affected by timely population management and control in Wuhan, which restricted it to a limited range. 2) There were four different transmission paths: imported family cluster units, imported non-family cluster units, imported and local family cluster units, and imported and local non-family cluster units. The first unit was most important, though the path of non-family cluster transmission was especially complex; epidemiological investigations should be strengthened along with prevention and control measures. 3) For imported cases, given the lag time from importation to onset and the longest time interval between the onset of cluster units, a small number of cases or carriers can break the 14-day isolation limit currently in use, such that caution should be exercised regarding possible risks associated with this measure. Based on these, three recommendations can be made for the prevention and control of COVID-19. 1) It is necessary to fully estimate the risk of future epidemic spread that may be brought about by the movement of people returning to work following initial quarantine, while strengthening epidemiological studies, actively exploring the spatio-temporal law of population flow and epidemic spread, and using science-based methods to prevent and control further viral spread. 2) It is necessary to persist in the prevention and control of population movements from Hubei and other high-risk epidemic areas. The 14-days quarantine currently in place throughout the country is effective for the vast majority of cases or carriers of the virus, but the results show that a few can break this limit, suggesting that the isolation time should be prolonged by up to 24 days. 3) The combined use of epidemiological investigation and geographic information technology should be strengthened to improve the timely tracking of epidemic occurrence and spread, accurately identify the activities of high-risk groups, and conduct accurate and effective source tracing, prevention, and control. In short, for a major public health crisis like the COVID-19 outbreak, emergency management and control should involve many scientific fields (including medicine, geographic & information technology, computer science, psychology, and behavioral science) in order to achieve timely and effective prevention and control measures that rely on such multi-disciplinary joint action.

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    Spatio-Temporal Characteristics and Impact Factors of Museums in Shanghai
    Zhuang Liang, Tian Na, Zhao Biao
    Tropical Geography    2020, 40 (3): 539-550.   doi: 10.13284/j.cnki.rddl.003215
    Abstract157)   HTML1)    PDF (2013KB)(39)      

    Based on a variety of Spatial Analysis techniques, this study examines the museums in Shanghai and discusses their time-space characteristics and the influences of space-time evolution mechanisms on them. The results show that the development of the said museums can be divided into three phases: exploration development (1978-1985), steady development (1986-1997), and high-speed development (1998-2016); and that the internal types of museums considerably differ from one another. Museums were also found to be primarily concentrated in the central city and along the Huangpu River, showing a typical “core-edge” diffusion feature. Additionally, their spatial distribution in the central city area followed a complex fractal structure radial trend and their development can be described as being gradually rich and diverse. At the same time, the spatiotemporal evolution of museums was discovered to result from the interactions between multiple factors: 1) The regional difference in historical and cultural resources, the most important factor affecting the development of Shanghai’s museums frames the basic pattern and main types of museum spatial distribution and limits the evolutionary trend of the aforementioned development. 2) The strategic orientation of government policies is also a key factor leading to the phased development and changes in these museums. This overall guidance and regulations gradually gave them a logical layout. 3) The financial support for regional development is a prerequisite to ensure the continuous improvement of the museums. 4) Spatial differentiation of regional population is an important influencing factor that causes differences in the museums’ spatiotemporal patterns. 5) And traffic access is the primary location condition that determines the spatiotemporal evolution trend of museums. These have all further strengthened the uneven distribution of museums. As a result, this article arrived at the following findings In terms of the process of benchmarking the construction of an “excellent global city” at a development level, Shanghai should work on further improving the indicators of the museum’s public service, cultural, and creative product revenue. It should insist on building museums to contribute to the cause of cultural preservation and growth as well as optimize its museum business model at the levels of incremental expansion and rational planning. With respect to quantity, it should actively explore museum resources and encourage the participation and investment of nongovernmental forces in museums. In terms of spatial layout, it should consider the balance of the geographical distribution in the various types of museums, break through the unipolar development model that focuses on the central urban area, specifically strengthen the construction of museums in the suburbs, and fully tap surrounding historical and cultural resources. In addition, it must promote the proper allocation of public cultural resources and the localization of its urban culture, thereby fostering the balanced development of museum spatial distribution.

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    Evolution of Ecosystem Service Value of Typical Dike-Pond in the Pearl River Delta:A Case Study of Foshan
    Han Ran, Ye Changsheng
    Tropical Geography    2020, 40 (3): 562-574.   doi: 10.13284/j.cnki.rddl.003249
    Abstract156)   HTML3)    PDF (2315KB)(173)      

    Dike-ponds are a type of ecological agricultural land formed by man-made depressions in ponds where silt is accumulated as dikes to farm fish and grow crops such as mulberry and sugarcane; they are mainly distributed in the Pearl River Delta. Ecosystem services refer to the living environment they provide for human beings, as well as the various types of ecosystem products and functions that are beneficial to human beings. In recent years, Ecosystem Service Value (ESV) has become a hot topic for scholars in China and abroad. Using the Pearl River Delta’s birthplace, Foshan City (FS), as a case study, the Millennium Ecosystem Assessment (MA) framework, which combines the characteristics of a dike-pond ecosystem and the social and economic conditions of the study area, is used to adopt the market price method, replacement cost method, and shadow engineering method to estimate the ESV of dike-ponds in FS in 2000, 2009, and 2017. Additionally, Dike-pond’s ESV in FS law of change was discussed and the influencing factors of ESV changes in dike-ponds were analyzed. The results show that during the study period of 2000-2017: 1) a few towns (streets) such as Lubao Town and Hecheng Street in the west and north, respectively, of FS have increased their dike-pond area, while Beijiao Town and Lecong Town in the east and south, respectively, have significantly decreased their dike-pond area to 19,244.47 hm2, which have been mainly transferred to construction land. 2) In 2000, 2009, and 2017, the ESV of dike-ponds in FS first decreased and then increased to 1,661.91×108 and 978.60×108, and 1,166.37×108 yuan, respectively. The overall trend is a declining one, with a total decrease of 495.54×108 yuan. In the three years, the proportion of adjustment functions in the total ESV is higher than 86%, which is the core function. Among the individual functions, the value of tourism and leisure increases the most, with an average annual growth rate of 19.36%. The value of climate regulation decreases significantly, by 589.37×108 yuan. 3) The ESV of dike-ponds in the southeast of FS is the highest. The western and northern regions are less affected by human activities and the ecological environment is suitable in this region; thus, the ESV of the dike-ponds increases accordingly. While the high level of industrialization and urbanization in the eastern and southern regions, serious pollution in the dike-ponds, and shrinkage of the dike-ponds all caused the ESV to decline, the material production and tourism and leisure values of the dike-pond of each research unit generally increased. The value changes of the remaining individual functions show strong consistency in space, i.e., the value of the towns (streets) in the northwest and southwest has increased significantly and the value in the southeast has decreased. 4) The results of a Geodetector probe show that a change in the Gross Domestic Product (GDP) of primary industries is the principal factor affecting the spatial distribution of the ESV of dike-ponds in FS, followed by the change in GDP, population density, population, investment in fixed assets, GDP of the secondary industries as well, and impact of policy factors, none of which should be ignored. Measures such as controlling the scale of development, restoring green vegetation, and giving importance to the advantages of the dike-pond landscape to increase the ESV of the dike-pond are all recommended.

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    Progress and Prospects in Rural Space Diversification, Reconstruction, and Governance from a Development Perspective
    Ren Yang, Xiuli Luo
    Tropical Geography    2020, 40 (4): 575-588.   doi: 10.13284/j.cnki.rddl.003240
    Abstract155)   HTML11)    PDF (1532KB)(116)      

    With industrialization, urbanization, informatization, and economic globalization, there is significant diversification in rural areas, including the social and economic devolopment and rural landscape, land-use structure, urban—rural relationship, consumption structure, and governance pattern. Development and evolution are types of spatial transformation, and their differentiation is significant in rural areas. With changes in the relationship between human beings and the environment in rural areas, problems such as the gradual disappearance of traditional villages, loss of regional identity, precariousness of villagers’ development prospects, and loss of autonomy tend to arise. The renaissance and revitalization of rural areas have become the core target of regional and rural development in this new era. Development, together with the theoretical construction of rural geography, now faces a critical period of opportunity. The mechanism of interaction between the internal and external motivations of rural spatial differentiation needs to be clarified, and geographic parameters concerning the reconstruction of rural multidimensional space need to be examined carefully, as they take a scientific approach in exploring comprehensive rural governance. These are beneficial in strengthening both rural construction and the framework of governance theory. This paper systematically reviews the progress of research on rural spatial differentiation, reconstruction, and governance both at home and abroad. We found that, internationally, research on rural geography is more diverse, and theories and methods from the field of political economics and sociology are widely used. These research methods are mainly qualitative, focusing on the theoretical interpretation of the construction and translation of the actor-network of cognition, differentiation, and reconstruction of rural space. Further, the main body and framework of rural community governance are analyzed deeply. Domestic research, in contrast, focuses on the differentiation and reorganization of rural material space, but the content framework and methodology of rural spatial differentiation, reconstruction, and governance remain insufficient. Accordingly, this paper—guided by the theory of territorial system of human—environment interaction on a macro scale—systematically examines the spatial differentiation types and dynamic mechanism of rural development and transformation under multiple external environments in China. On a medium-micro scale, the comprehensive study of the rural human—environment relationship in a regional system is implemented, focusing on element structure, function change, element reconstruction, and space governance. We performed a space gradient analysis using urban—rural continuous spectrum geographic transects, which analyzed internal multidimensional space differentiation and reconstructed the scientific logic of governance in different locations and with different types of rural space. By integrating geography, sociology, politics, management, and other subjects, we constructed a unique theory framework for the transformation of rural space in China. Rural space governance is an important part of territorial space control and social governance, and is of interest across multiple academic disciplines. The collaborative mechanism between the governance of space and the participating community, as well as the approaches and models of village construction management and spatial governance used, needs an urgent conclusion and summary.

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    Migration Characteristics and Return Migration Intentions of Migrants in the Context of New Urbanization
    Yongfei Xie, Yanqing Ma, nd Li Hongjuan
    Tropical Geography    2020, 40 (4): 612-624.   doi: 10.13284/j.cnki.rddl.003245
    Abstract155)   HTML6)    PDF (1270KB)(73)      

    Drawing on data from the 2016 "Migrants' Dynamic Monitoring Survey", using descriptive analysis and three multinomial logistic regression models, this paper describes the latest status and characteristics of return migration intentions, and explores the relationship between migration characteristics and return migration intentions. Findings showed that migrants’ return intentions is particularly weak; more than 40% of migrants plan to return in the near future; the return regions are diverse and dispersed. They present a multi-location interactive mode of "destination place, namely the original location as the main part and administrative townships and counties (districts) as the auxiliary part." Among the migrants who return to their administrative townships and counties (districts), the proportion of those who return to their administrative county is higher than that those who return to their administrative township. The results of the models show that migration characteristics have a significant influence on return migration intentions. Intra-provincial migrants are more likely to return than inter-provincial migrants. Compared with migrants with shorter migration times, migrants with longer migration times are more likely to return; to do so within 2 years; and return to their point of origin. Migrants within the category of non-whole family migration are more likely to return; to do so within 2 years; and return to their point of origin than in the case of whole-family migration. Compared with migrants who have no children left behind, migrants who have left children behind are more likely to return and to do so within 2 years than those who have not. Migrants' return intentions is obviously influenced by characteristics such as career, income, education level, age, and other variables. Relatively speaking, those with lower occupational prestige, income and education levels and those of older age are more likely to return. Based on the above results, it is suggested that the government should implement the strategy of “holding local citizenization as essential, with reflux citizenization as a supplement”; continue to deepen systemic reform to clear up institutional barriers and provide equal public service to migrant workers; and promote the economic and social development of the Central, Western and Northeastern regions, formulating preferential policies to encourage farmers to return.

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    Spatio-Temporal Evolution, Influencing Factors, and Diffusion Model of Golf Courses in China
    Jin Wanfu, He Guangjing, Chen Le
    Tropical Geography    2020, 40 (3): 515-524.   doi: 10.13284/j.cnki.rddl.003234
    Abstract154)   HTML3)    PDF (1334KB)(41)      

    This study examined the spatial diffusion of golf courses in mainland China from 1984 to 2016 through the application of spatial analysis and mathematical statistics. We found that since the early 1990s, the central government has introduced policies to limit course expansion. However, it was not until 2014 that the rapid national expansion of course construction was brought under control. Overall, the number of courses experienced a low-rate expansion period in 1984—1994, a steady expansion period in 1995—2004, an accelerated expansion period in 2005—2013, and a contraction period in 2014—2016. The spatial distribution of courses has also experienced expansion and contraction periods, with the most significant spreading occurring northward and westward. Golf courses are clearly clustered in China. The Yangtze River Delta, Pearl River Delta, Bohai Rim region, and capital cities in central and western China that feature relatively high levels of economic development, more outward-looking economies, and dense populations have larger numbers of courses, indicating that the spatial distribution of golf courses in China is affected by socioeconomic factors. Correlation analysis further showed that socioeconomic factors such as per capita GDP, population size, regional openness, and transportation dominance are significantly positively related to the spatial distribution of courses, with transportation dominance having the greatest impact. There were 115 golf courses in six transport hub cities, accounting for 25.96% of the total. It is worth noting that despite the scarcity of land resources in China, local governments are interested in building courses to develop tourism and leisure industries and attract foreign investment. There is also a significant positive relationship between the scarcity of land resources and the spatial distribution of courses. The spatial diffusion model of courses was characterized by a degree of regularity. Specifically, courses first appeared in the coastal areas with developed economies and a high degree of openness to the outside world, and then spread to surrounding and inland areas, demonstrating obvious contact diffusion characteristics. In addition, metropolitan areas first built courses, and then surrounding lower-level cities also built courses in Bohai Rim and the Yangtze River Delta regions. The spatial state model further confirms that golf courses in China present obvious contact and hierarchical diffusion characteristics. This study’s findings promote a better understanding of the spatial diffusion patterns of golf courses in China since the reform and opening up and further enrich the theoretical study of the spatial diffusion of sports culture in Chinese human geography.

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    Spatial Differentiation and Influencing Factors of Beautiful Village in Guangzhou
    Zhang Chen, Xiao Dawei, Huang Yi
    Tropical Geography    2020, 40 (3): 551-561.   doi: 10.13284/j.cnki.rddl.003216
    Abstract150)   HTML5)    PDF (1629KB)(48)      

    At present, along with rapid urban-rural transformation, rural development faces a new round of challenges. Under the progressive drive of urban-rural integration development, new countryside construction, and the rural revitalization strategy, rural development has been gradually receiving attention. Since 2013, many nationwide rural construction practice explorations have been carried out. Among them, local practices represented by beautiful village construction have achieved staged results. In this context, based on four batches of 160 village construction pilots published by Guangzhou from 2013 to 2016, the research attempts to explore spatial differentiation characteristics of the beautiful village in Guangzhou and its influencing factors using GIS spatial analysis methods such as the nearest neighbor index, multi-distance spatial clustering analysis based on Ripley’s function, kernel density analysis, and overlay analysis. Based on a geospatial perspective, this study attempts to provide a phased assessment of the current spatial distribution of beautiful village, to expand the spatial dimension of this kind of village and “village cluster” study. First, since 2013, the number of beautiful village in Guangzhou has increased year by year and the growth rate is on the rise. At the same time, their spatial distribution presents obvious concentrated characteristics. Nuclear density analysis shows that high-density areas of these villages are mainly distributed in the south and northwest of Guangzhou, including one hotspot main core area of Panyu-Nansha and two hotspots sub-core areas of Conghua and Huadu-Baiyun. The density distribution shows a multi-core imbalance. Second, the main factors affecting the spatial distribution of these villages include topography, hydrology, human population, history, transportation, location, policy, and planning. Among them, topography and hydrology constitute the basic motivation for rural development; deep historical and cultural resources are the spiritual driving force to support the continuous development of rural areas; transportation and location are a key positive factors affecting rural development; policy and planning factors have a decisive influence on the "beautiful village cluster" spatial pattern, which is manifested in government efforts to promote the concentration of village space through the formulation of selection criteria, post-construction evaluation and acceptance mechanisms, construction action plans, and "beautiful village cluster" planning. Guangzhou beautiful village planning and construction has achieved initial results and gradually formed “beautiful village clusters” based on the hotspot core areas. This kind of government-led village pilot construction has promoted village spatial concentration but has exacerbated uneven development among villages. Therefore, under the strategy of rural revitalization, we should strengthen the diversity and locality of the selection of village pilots, push forward the transformation of "village cluster" from spatial concentration to industrial agglomeration, pay attention to the pluralistic value of these villages, and explore new models of governance led by communities, to explore new directions for rural development.

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    See the World from a Mobile PerspectiveA Review on “Mobility” Edited by Peter Adey
    Cai Xiaomei, Bu Meiling, Li Jun
    Tropical Geography    2020, 40 (3): 455-465.   doi: 10.13284/j.cnki.rddl.003250
    Abstract145)   HTML2)    PDF (771KB)(30)      

    Social mobility is transforming the way we survive , as well as our place of residence and production. Studies in mobility have evolved from a dispersive and independent mode to a multi-disciplinary form, led by geography and sociology , and have become a new multilevel interdisciplinary paradigm. Peter Adey’s Mobility (2nd Edition) is a classic textbook sorting out the evolutionary research path of mobility, interpreting its theories, and citing cases and methods from previous studies. This study summarizes main aspects of this book based on the background for the mobility research, its main contents, research methods, etc. Instead of dualism, future work could adopt networking and dialectical approaches to contemplate the world before conducting research on mobility. Additionally, future studies need to be grounded in a thorough understanding of the meaning, politics and practice of mobility, and related media. This study further suggests the conduction of future studies within the context of the politics of mobility, the spatiotemporal dimension of mobility, its relation to tourism, etc.

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    Spatial Agglomeration and Factors Influencing of Secondary Vocational Education in China during 2000‒2016
    Wang Hui, Yan Junping, Peng Bangwen, Liu Dongmei, Lian Lijuan
    Tropical Geography    2020, 40 (3): 525-538.   doi: 10.13284/j.cnki.rddl.003209
    Abstract138)   HTML0)    PDF (2682KB)(20)      

    The economic and social transformation and reconstruction in China has prompted the government to focus its attention on the role and influence of vocational education on the development of the manufacturing industry and improvement of social equity. Secondary vocational education is an important part of popularizing high school education and developing modern vocational education in China. It is the foundation of constructing a modern vocational education system. It is of great significance for the cultivation of middle-level skilled technical talents and the improvement of the labor market. Based on statistical data of the development of secondary vocational education in 31 provinces and regions in mainland China from 2000 to 2016, this study focuses on the spatial clustering characteristics and factors influencing the development of secondary vocational education. The study adopts methods such as geographical concentration, spatial autocorrelation analysis, geographical detector, etc., to explore the following issues: How will China’s secondary vocational education change in a spatiotemporal context? Is there spatial agglomeration? What are the factors that cause the spatial agglomeration of secondary vocational education? This study shows that the development of secondary vocational education in China followed an inverted "U" trend from 2000 to 2016, and the geographical concentration of students in the provincial level is gradually increasing. The provinces with large-scale secondary vocational education include Guangdong Province, Henan Province, and Shandong Province. The development of secondary vocational education in more than one-third of the provinces in China is characterized by small scale and slow growth, as seen in Beijing, Tianjin, Shanghai, Fujian, Hubei, Shaanxi, Shanxi and Northeast China, while the "growth" provinces are all distributed in southern China, including Anhui, Jiangxi, Hunan, Guangdong, Guangxi, Yunnan, Guizhou, Sichuan, etc. From the perspective of spatial relationship, there is a significant spatial autocorrelation between the level and growth of secondary vocational education from 2000 to 2016, but the degree of spatial agglomeration has declined; this indicates that the spatial balance of secondary vocational education is constantly improving. In addition, the overall level of secondary vocational education shows a trend of "moving south." The hotspots have moved from North China to Southeast, Central, and South China. Shandong, Henan, and Anhui provinces are always included as hotspots of secondary vocational education. The hotspots of secondary vocational education growth are mainly distributed in the western region, and show a transfer process from northwest to southwest. Tibet is always in a hotspot of growth. The main factors influencing this pattern of change are the population of school-age children and secondary vocational education development conditions, while the role of regional economic development level is relatively small. The interaction between different factors significantly affects the changes in the spatial pattern of secondary vocational education, mainly through interactions between the number of junior high school graduates and other factors.

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    General Characteristics and Knowledge Maps Visualization Analysis of Human Settlement Research in China
    Wang Yi, Lu Yuqi, Zhu Yingming, Ding Zhengshan
    Tropical Geography    2020, 40 (3): 498-514.   doi: 10.13284/j.cnki.rddl.003212
    Abstract135)   HTML0)    PDF (3094KB)(35)      

    Along with environmental problems that constantly emerge due to rapid industrialization and urbanization, human settlement, an ancient and new field in the man-land relationship research, is attracting increasingly wider attention in academia. Taking the China National Knowledge Internet (CNKI) and Chinese Science Citation Database (CSCD) as the literature search engines, and based on the platform of CiteSpace, this paper analyzes and summarizes the general characteristics and the mapping knowledge domain of human settlement research from 1992 to 2017 in China. The results show the following: 1) There has been a significant increase in the number of published articles on Chinese human settlements, and the Architectural Journal, City Planning Review, and Urban Development Studies are the main journals for publication. 2) The most competitive research institutions and teams are mainly found in the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (CAS), as well as in other architectural & planning and normal universities, such as Liaoning Normal University, Tsinghua University and others. 3) As for the funding sources, there is an obvious diversification trend with national funding being the primary source of research grants. 4) In terms of key research areas, human settlement, residential environment, livable city, human environment, sustainable development, living space, and the like have been focused on for a long time. 5) In terms of the research topics and intellectual base, the research content on human settlement is relatively broad, and there is no focus on any specific topic. Based on 31 classic articles, "Urban human settlements”, “livable city”, “rural human settlements”, “residential environment”, “nature suitability”, “residential satisfaction”, “sciences of human settlement”, and “population development” are 8 hot topics. 6) As for the evolution route, the development of research on human settlements in China has shown a clear evolutionary process and has a strong problem orientation and policy research orientation. Stages and dynamics of socio-economic development, as well as problem and policy orientations of research are the main driving forces for its evolution. In addition, the cooperation and exchange among scholars, interdisciplinary integration, and the innovation and application of new technology and methods can also promote its evolution. Throughout the history of Chinese human environment research, scholars have always focused on the nation's requirements, focusing on the two central elements (i.e. human and environment) of human settlements and their relationship. However, the understanding of related studies of theoretical cognition, research object and content, and research scale and method should also be further deepened and expanded. This paper clarifies the context of the development of the science of human settlements in terms of time, deepens the understanding and grasp of the human settlement research, as well as provides scientific reference for subsequent research.

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    Spatio-Temporal Evolution of Shawan Ancient Town in Guangzhou from the Perspective of Spatial Syntax
    Wei Tao, Kefeng Lin, Hengyu Gu, Chaoming Liao, Shiying Liu, Qianyi Ou
    Tropical Geography    2020, 40 (6): 970-980.   doi: 10.13284/j.cnki.rddl.003282
    Abstract135)   HTML6)    PDF (3912KB)(91)      

    Against the background of the construction of the Guangdong-Hong Kong-Macao Greater Bay Area, the development of ancient towns is faced with new challenges, such as the expansion of urban scale, the weakening of traditional cultural values, the lack of continuity between new and old urban areas, and the inconsistent pattern of old urban areas. This research takes the Shawan Ancient Town, Panyu District, Guangzhou City, as its research object and conducts a spatial syntactic analysis of urban morphology in 2002, 2008, and 2017, based on the axis model. The research shows that: 1) Shawan Ancient Town has experienced three stages of development in terms of overall shape, from "single nucleus cohesion" to "axis growth" and then to "divergence and spread." The town's core has been expanding and its shape has been perfected. 2) The direction of expansion of the ancient town's spatial form is consistent with expansion in the direction of the integrated nuclear center, with which the town's new business is in line. The central transfer is synchronized with the evolution of the spatial form. 3) The phenomenon that the integration core of ancient towns and the development of commercial centers are out of sync is related to modern cities' orthogonal grid form and traditional ancient towns' relatively dense and complex spatial texture. This study reveals the law of development of the traditional village spatial form in the process of rapid urbanization and provides a useful reference for the traditional village's new spatial design and the inheritance and reconstruction of the spatial development structure and order. Finally, the research proposes the following suggestions for the spatial protection of ancient towns: 1) The development of ancient towns should extract the spatial rhythm from the traditional space and follow similar rules to update and develop the town, so as to protect the sense of scale and the traditional daily living space. 2) Good traffic planning can ensure that the original space is only minimally affected. At the same time, the use of transit rail to connect the ancient towns old and new districts can improve continuity between the spaces and ensure efficient operation. 3) Demonstrating the need for the rational control of tourism development., Shawan Ancient Town is in the stage of high tourism development, which makes residents' living space overlap with tourists' visiting space, often resulting in the occupation and destruction of the original settlement space to meet the needs of "others." As a characteristic element of traditional ancient towns, their protection and continuation need to be respected during tourism development. Planning should fully analyze ancient towns' spatial rules and development needs to avoid excessive transformation of the space due to commercial development and the timely restoration of some places worth preserving" if applicable..

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    Construction of Sense of Place and Rural Governance:A Case Study of Chaoshan Ancestral Hall
    Yuangcheng Lin, Ren Yang, Qiuping Lai, Min Wang
    Tropical Geography    2020, 40 (4): 732-743.   doi: 10.13284/j.cnki.rddl.003257
    Abstract134)   HTML3)    PDF (2242KB)(27)      

    In the vast rural areas of southern China, ancestral halls, being material space carriers with common historical culture and value identification as the core, play an important role in the cultural shaping and governance of rural society. However, with the rapid spread of modern elements and modern culture, many Chaoshan rural areas are facing the dilemma of cultural identity and cultural confidence. What kind of cultural identity, local affiliation, and emotional expression do Chaoshan ancestral halls bearing local culture and local significance have in the daily practice of local subjects? How to construct the local meaning around Chaoshan ancestral hall and then realize the cultural space with multiple connotations? On the path of seeking cultural confidence in rural areas, what is the internal logic of Chaoshan ancestral hall and rural governance, and how to achieve the revitalization and co-governance of rural regional space? These are questions worth thinking about and exploring further. In view of the same, this article researches the breakthrough point, with Chaoshan ancestral hall and its links to the local villagers, ancestral hall management personnel, and grass-roots workers as the research objects. We used the network file analysis, in-depth interview, and questionnaire-based survey research methods, exploring the Chaoshan ancestral hall where the construction process and the culture mechanism to better resolve the Chaoshan multi-agent ancestral hall and the village of dialogue and interaction. First, Chaoshan ancestral hall, as a material entity connecting and maintaining rural social network, plays a significant role in shaping the sense of place of rural spatial subjects. To be specific, Chaoshan ancestral halls have formed rooted cultural identity and shaped common symbols, cultural concepts, and behavioral norms in the long-term historical evolution, which act on local cognition, emotion, and intention, making Chaoshan ancestral halls continuously strengthen local perception and local practice of rural subjects. Additionally, Chaoshan ancestral hall has become a very local physical landscape in rural areas through localization and stability of architectural form, highlighting local characteristics, and local significance in increasingly homogeneous rural areas. The construction of locality is a process from material to spiritual, the “time and space” of Chaoshan ancestral hall represents the transformation from materiality to spirituality, and the meaningless place is shaped into a place with roots and attributes. The cultural confidence in rural areas is in an urgent need of the construction of local identity and local attachment so as to realize the transformation of rural areas from being culturally “lost” to culturally “rooted”. The interaction between Chaoshan ancestral hall and many subjects in rural areas forms a sense of place, which provides an emotional and cultural basis for rural governance. Admittedly, rural regional space has its own complexity, so rural governance is bound to be multi-subject, multi-dimensional consultation, and co-governance. Based on local culture and material function, multi-subject creation is an important mode of rural governance. Clan council derived from Chaoshan ancestral hall plays an irreplaceable role in coordinating and dealing with rural affairs.

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    Application of GF-2 Satellite Data for Monitoring Organic Pollution Delivered to Water Bodies in the Guangdong-Hong Kong-Macao Greater Bay Area
    Di Wu, Wenjin Yu, Tao Xie
    Tropical Geography    2020, 40 (4): 675-683.   doi: 10.13284/j.cnki.rddl.003259
    Abstract125)   HTML9)    PDF (2272KB)(35)      

    Remote sensing technology for monitoring of water pollution has the advantages of wide monitoring range, fast monitoring speed, low cost, and long-term dynamic monitoring. To explore the applicability of the GF-2 earth observation satellite in the monitoring of organic pollution delivered to water bodies, this study extracted water body information from the normalized difference water index based on GF-2 earth observation multi-spectral data and used the Ratio Vegetation Index (RVI) to obtain the water quality classification and organic pollution distribution of six major rivers in the Guangdong-Hong Kong-Macao Greater Bay Area in March 2019. To reflect the water quality classification and water pollution distribution more clearly and intuitively, this study used ArcGIS software to visualize the water pollution information. According to their different degrees of organic pollution, the water bodies were categorized into the four levels of pollution-free, light pollution, moderate pollution, and heavy pollution, respectively, corresponding to the blue, green, yellow, and red colors in the figure, and the classification results of each river section were developed using area statistics. Finally, the water quality indexes of measured data were classified and evaluated according to the single water-quality parameter evaluation standard of surface water. The classification map of organic pollution was verified by comparing it with the remote sensing analysis results. The results of the study are as follows.: 1) The water quality of the study area is generally good. The Jitiemen and Jiaomen watercourses mainly have light pollution, whereas the Modaomen watercourse, Dongjiangnan tributary, Hengmen watercourse, and Hongqili watercourse are mainly pollution-free, with generally good water quality. 2) The distribution of organic pollution shows a spatial pattern. The main channel of the river is mainly a pollution-free water body; the two sides of the river have mainly light pollution, and the closed water body away from the main river has mainly medium pollution and heavy pollution. Timely and effective water pollution prevention and control measures need to be taken according to local conditions. 3) The extraction of organic pollution information from GF-2 multispectral data is feasible. The water bodies of JiTimen bridge, MoDaomen bridge, HongQili, and Jiao Men belong to the pollution-free class of water bodies. The ShatianShisheng is a water body of four types, with dissolved oxygen and ammonia nitrogen parameters exceeding the limit, and the ZhongShan port wharf is a water body of three types, with ammonia nitrogen parameters exceeding the limit. Both of these are mildly polluted water bodies with respect to organic pollution. The pollution levels of the six monitoring sections analyzed by remote sensing are consistent with the evaluation results of the actual monitoring sites in March 2019. The study concluded that GF-2 earth observation satellite multi-spectral data are accurate and reliable as a remote sensing data source for water pollution monitoring. These data can provide auxiliary information for decision-making pertaining to water pollution prevention and control in China. The research method of water body classification using the RVI implemented in this study is a semi-quantitative analysis method, which cannot be used to analyze specific water quality parameters quantitatively. The next step is to establish a chlorophyll concentration inversion model, which would allow the specific chlorophyll concentration data of each detected water body to be obtained quickly.

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    Spatial-Temporal Characteristics, Danger Simulation, and Boundary Detection of Malaria during the Qing Dynasty (1644‒1911)
    Li Zimo, Chen Danyang, Wang Xiaowei
    Tropical Geography    2020, 40 (3): 446-454.   doi: 10.13284/j.cnki.rddl.003251
    Abstract124)   HTML3)    PDF (1252KB)(21)      

    Malaria is an insect-borne infectious disease transmitted by anopheles. It was widespread in China about 3,000 years ago and continues to pose a severe threat to human life and health. Taking the Malaria epidemic during the Qing Dynasty as the research object, and using Excel, Geographic Information System (GIS), MaxEnt, and BounderSeer, the following results were obtained: 1) Malaria was one of the most common diseases during the Qing Dynasty. During fifty-nine of the total of 268 years of the Qing Dynasty, Malaria was widespread, with a frequency of 22.01%. The disease spread to 17 provinces, leading to an epidemic situation in a total of 210 counties, covering an area of 340,400 km2. This area accounted for approximately 2.69% of the total malaria-epidemic area during the Qing Dynasty. Malaria outbreaks frequently during the seasons of autumn and summer. These two seasons account for 85.23% of the total pandemic years and 92.47% of the pandemic-struck counties. Consequently, autumn and summer are targeted for the prevent and control of the Malaria pandemic. 2) Genetic adaptations to Malaria parasites is highly adaptable in China, with the southeast being the most optimal place for the mosquitoes to thrive. As per the distribution pattern, the risk of Malaria decreases from the southeast to northwest, of which, the Jiangsu, Anhui, Shandong, Henan, Hubei, and Hunan provinces have higher risks of Malaria. Various environmental factors affect the prevalence of Malaria with altitude, minimum temperature, and annual temperature difference as the main factors, with respective contribution rates of 44.4%, 16.3%, and 10.6%. 3) The geographical boundaries of Malaria were clearly established. The Malaria epidemic during the Qing Dynasty presented the boundary characteristics of "two horizontal and three vertical." The first horizontal boundary at the 40°N line and the second at the Nanling line were, respectively, the northern boundaries of Malaria and falciparum Malaria (pestilence). The first vertical boundary was an arc with Huoshan at its center. Using the straight-line distance between Huoshan and Hongya (approximately 1,250 km) as the radius, this area accounted for 96.67% of the Qing Dynasty Malaria pandemic. The second vertical boundary was the boundary line of the highly adaptable area of the Malarial mosquito, which included the eastern and central provinces of China. The third vertical boundary was the enclosure area based on the main Malaria network, covering the Yangtze River Delta region. However, the risk levels and boundary characteristics of the Malaria pandemic were not invariable and changed based on the natural and social environments. For example, the high-risk Malaria-endemic areas of the Qing Dynasty included Hubei and Hunan, with lower levels of risks in Sichuan, Yunnan, and other provinces, which still continue have low levels of risk. Investigating the temporal and spatial characteristics, risk levels, and boundary characteristics of the Malaria epidemic during the Qing Dynasty is expected to provide a historical basis for the improvement of the present Malaria control system, as well as a historical reference for dealing with sudden Malaria outbreaks.

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