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10 January 2021, Volume 40 Issue 1 Previous Issue   
Plateau Science and Sustainable Development
Research progress on the sustainable development of Qinghai-Tibet Plateau
GAO Qing, MIAO Yi, SONG Jinping
2021, 40 (1):  1-17.  doi: 10.11821/dlyj020200614
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The Qinghai-Tibet Plateau, also known as the roof of the world, the water tower of Asia and the third pole of the earth, profoundly affects the ecological security at the national and global scales. But its harsh, sensitive and fragile natural environment has long been constraining local socio-economic development. It is an inevitable requirement for Qinghai-Tibet Plateau to take the path of sustainable development in order to balance the socio-economic development with ecological protection. In this context, it is necessary to summarize the relevant research results on the sustainable development of the Qinghai-Tibet Plateau so as to promote the transformation of the relevant research into targeted, operable and implementable policy reference in the regional sustainable development. Therefore, this paper selects 1416 Chinese papers and 120 English papers related to the sustainable development of Qinghai-Tibet Plateau by conditional search based on the database of China National Knowledge Infrastructure (CNKI) and Web of Science (WOS). And this paper uses the CiteSpace 5.7.R2 visualization software to carry out bibliometric analysis such as keyword co-occurrence network analysis and institutions cooperation network analysis based on these papers, and further thoroughly reviews the progress of related research. This paper finds that the study of the sustainable development of the Qinghai-Tibet Plateau has experienced the slow rising stage (before 1999), the accelerated rising stage (1999-2009), the fluctuant decline stage (2009-2017) and the new development stage (after 2017). By combing the relevant research, it is also found that scholars have made a rich exploration on the sustainable development of the whole region and systems of Qinghai-Tibet Plateau from many aspects such as the interaction among systems, practices, countermeasures and evaluation. However, there are still some problems in the research content, the perspectives and the methods. There is an urgent need to make further research in the mechanisms and influencing factors of multi-scale regions from the interdisciplinary perspective with multiple research methods, deepen the understanding of the sustainable development of Qinghai-Tibet Plateau, and summarize and explore the sustainable development paths of different function areas so as to build a basic theoretical framework for the study of the sustainable development of Qinghai-Tibet Plateau.

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Ecosystem service trade-off and synergy on Qinghai-Tibet Plateau
CHEN Xinmeng, WANG Xiaofeng, FENG Xiaoming, ZHANG Xinrong, LUO Guangxiang
2021, 40 (1):  18-34.  doi: 10.11821/dlyj020200399
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The Qinghai-Tibet Plateau is known as the "third pole" of the world. With the global changes and frequent human activities, its ecological problems are exacerbated. Analysis of the spatiotemporal changes of ecosystem services and trade-off synergy has important significance for the coordinated development of the ecological environment and economy in the Qinghai-Tibet Plateau. Based on climate regulation services, carbon sequestration and water production services, we combine remote sensing, meteorology, land use and other multi-source data, and use pixel-by-pixel correlation analysis to study the spatiotemporal dynamic characteristics of trade-offs and synergies in long-term sequences in the study area. The results showed that: (1) From 1990 to 2015, all the three ecosystem services presented a spatial distribution pattern, in which water production, carbon sequestration, and climate regulation increased from northwest to southeast. In the 26 years, water production services and climate regulation services showed a trend of increasing volatility, and inter-annual fluctuations in carbon sequestration services rose slightly. (2) Among different land use types, the three types of services in the forest land type are generally higher in value, while the values of carbon sequestration and climate regulation in the water body type are lower, and the value of water production is higher. In terms of land use types in 2015, the value of water production services was listed as forest land > water body > grassland > cultivated land; the value of carbon sequestration was presented as forest land > arable land > grassland > water body; the value of climate regulation was forest land > grassland > arable land > water body. (3) In the Qinghai-Tibet Plateau, there is a trade-off relationship between climate regulation and water production, carbon sequestration and water production. Climate regulation and carbon sequestration services have a mutually reinforcing synergistic relationship. Carbon sequestration and climate regulation are closely related. The correlation between climate regulation and water production is the weakest. (4) Under the protection scenario, the climate and water production exhibit a weak synergy relationship, with the strongest synergy between climate and carbon sequestration, and the weakest balance between water production and carbon sequestration, which is most conducive to the healthy development of the ecological environment of the Qinghai-Tibet Plateau.

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Impact of climate change and engineering activities on spatio-temporal changes of vegetation index along Qinghai-Tibet Railway
MA Chao, CUI Peipei, ZHONG Guangrui, MENG Meng, YANG Cheng, MA Wensi
2021, 40 (1):  35-51.  doi: 10.11821/dlyj020200528
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The fragile ecological zone of the Tibetan Plateau is extremely sensitive to human activities and global changes. To reveal the response characteristics of the normalized difference vegetation index (NDVI) to engineering activities and climate changes in the direct impact area and ecological check area (CK) of the Qinghai-Tibet Railway construction, GIMMS AVHRR NDVI3g plus data (1982-2015), MODIS NDVI data (2001-2018), and meteorological data from the same period were selected in this study. Using the maximum value compositing (MVC) method, the annual maximum NDVI and interannual average NDVI of the direct impact area (8-km buffer zone) and CK (16-km buffer zone) along the Qinghai-Tibet Railway were obtained, and trend, variation, correlation, and residual analyses were performed. The results show the following aspects. (1) Using spatio-temporal pseudo-invariant features, the spatial heterogeneity component and periodic greenness component from vegetation coverage were eliminated, and the contribution of climate change and engineering activities were identified. (2) The annual NDVI along the Qinghai-Tibet Railway was highly responsive to climate change and engineering activities. In the early stage of construction, the annual NDVI mainly responded to climate change, and the annual NDVI showed a slowly rising trend. In the middle stage of construction, it mainly responded to engineering activities, and the annual NDVI showed a significant downward trend. In the operation of the railway, it responded to a combination of climate change and engineering activities, and the annual NDVI slowly increased. (3) The engineering activities of the Qinghai-Tibet Railway had a significant impact on the vegetation along the railway. In the early stage of construction, the annual NDVI growth rates in the direct impact area and CK were similar. In the mid-construction period, the annual NDVI growth rate in the direct impact area was lower than that in the CK. In the operation of the railway, the annual NDVI growth rate in the direct impact area was higher than that in the CK. (4) From 1982 to 2015, climate change along the Qinghai-Tibet Railway responded significantly to global change. In the Xining-Golmud section, the temperature increase rate was 0.57°C/10a, and the precipitation growth rate was 4.67 mm/10a; in the Golmud-Lhasa section, the temperature increase rate was 0.20°C/10a, and the precipitation growth rate was 1.78 mm/10a. Both temperature and precipitation increased.

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Phenological characteristics of alpine arid region based on biome type and its responses to climate factors: A case study of Qaidam Basin from 2000 to 2019
FU Yang, CHEN Hui, ZHANG Siqi, YANG Yi, ZHAO Yuanjie
2021, 40 (1):  52-66.  doi: 10.11821/dlyj020200327
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Vegetation phenology reflects the adaptation of vegetation to the comprehensive environment. Phenology research is of great significance to understand the growth mechanism of vegetation in the ecosystem and its response to ecological factors, especially climate factors. Based on the MODIS NDVI data and Double Logistic Function fitting method, the vegetation phenology in the typical alpine arid region of Qaidam Basin from 2000 to 2019 was selected as the object. The characteristics of static state (spatial heterogeneity) and dynamics (temporal and spatial change) of vegetation phenology and their responses to climate change were studied at the regional and biome levels. The results are as follows. First of all, in Qaidam Basin, the start of growth season (SOS) and the end of growth season (EOS) were mainly advanced. Specifically, the start of growth season was 0.13 days/yr in advance and the end of growth season was 0.23 days/yr in advance. With regard to the end of growth season, 57% of the vegetation areas had a significant advance level (P<0.01). The length of growth season (LOS) was mainly shortened. The trend of shortening was 0.09 days/yr. Secondly, there was a positive correlation between the start of growth season and the end of growth season in spatial distribution and variation trend. In the region where the start of growth season occurred earlier, the end of growth season occurred earlier, and vice versa. The region where the variation trends of the start of growth season and the end of growth season were both in advance showed an obvious overlapping. The last but not the least, the combination of water and heat has obvious restrictive effect on vegetation phenology. No matter in distribution or variation trend of phenology, the start of growth season and the end of growth season were affected more significantly by precipitation, and the response of variation trend to precipitation was faster. Under the alpine arid condition, there was more precipitation in warm steppe and shrub, resulting in the longest growth season, 131 days and 128 days respectively. And the shortest growth season occurred in the alpine meadow (113 days).

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Time series monitoring and analysis of hydrological change process of Sarez Dammed Lake from 1972 to 2019 by multi-source remote sensing
WANG Xiang, ZHU Changming, ZHANG Xin, WANG Weisheng, FANG Hui
2021, 40 (1):  67-80.  doi: 10.11821/dlyj020200383
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The hydrological characteristic process of the dammed lake has practical guiding significance and scientific reference value for the macro-control, forecast and early warning, safety prevention and control of floods in the reservoir area. In order to acquire and grasp the hydrologic characteristics and historical evolution process of the Sarez Dammed Lake in Pamir Plateau in time, the spatiotemporal changes and hydrologic evolution process of this dammed lake from 1972 to 2019 are comprehensively and systematically analyzed by using the intensive time series remote sensing data and the measured data of the hydrological station. And through the "area-water level" relationship model, we reconstruct the historical water level and historical area evolution sequence process of the Sarez Dammed Lake from 1972 to 2019. On this basis, the Mann-Kendall trend and mutation test method is adopted to analyze the hydrological change of the lake. The research results show that: (1) In general, the water level process showed a significant upward trend in volatility, and this volatility trend was mainly manifested in fluctuations and high oscillations during the year, but the amplitude of the rising water level was decreasing year by year. (2) In terms of the hydrological evolution, the hydrological characteristics had an abrupt inflection point around 2013, where the lake area and water level changed from the original slow increase to the accelerated rise. (3) The relationship model between the area and the water level of the Sarez dammed lake is: y=-0.1003x2+18.181x+2440 (R 2=0.63, P<0.05, two tail). Combined with the analysis of river basin meteorology, runoff and related literature data, it is concluded that the intra-annual/inter-annual hydrological fluctuations of the lake are directly affected by the runoff recharge of the upstream Murgabu River. In terms of the causes of hydrological changes, we believe that the increase of river runoff caused by the accelerated melting of plateau glaciers and snow under the environment of global warming is the main reason for the accelerated increase of the area and water level of the lake in recent years.

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River terraces in the northern Guizhou Plateau and their implications for karst landform evolution
JIANG Xi, CHEN Wenqi, NING Fan, SUN Yuhui, AO Jin, LUO Weijun, KUANG Guangxian
2021, 40 (1):  81-92.  doi: 10.11821/dlyj020200485
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Geologists pay much attention to mountainous geomorphic evolution of Guizhou Plateau, because of its core region of karst area in Southwest China. There are two different geomorphic blocks in the northern Guizhou Plateau, which is representative for the karst landforms in Guizhou. River terraces in the karst intermontane basin, as an important step-like landform system in this area, are of great significance for the study of regional geomorphic evolution. In this work, we studied sediment characteristics and optical stimulated luminescence (OSL) dating of the terraces in the Suiyang Basin and the Wangcao Basin in the northern Guizhou Plateau. And then, the terrace ages and associated evolutionary dynamics of Guizhou Plateau have been discussed. Combining the terrace development and geological background, we explored karst landform evolution of northern Guizhou Plateau. It is found that in the Suiyang Basin, the ages of terrace are ranged between 18.8 ka-8.2 ka for T1 and 144.4 ka-104.1 ka for T2. In the Wangcao Basin, the ages of terrace are 5.5 ka for T1 and 45.1 ka for T2. In the Suiyang Basin, the terraces mainly deposited floodplain sandy sediments, while the terraces in the Wangcao Basin mostly cut the thick dolomite bedrock. The dating results show that in the formation stage of terrace T1, the average cutting rate of the Furong River in Wangcao Basin is 1.67 m/ka, significantly greater than that of the Yangchuan River in the Suiyang Basin, which is 0.35 m/ka. According to dating and regional geological correlation, we hold that climate change may affect the sedimentary characteristics of the terraces, but tectonic uplift is the dominant driving force for terrace formation. Different terrace ages are the results of differential uplifts in the Guizhou Plateau. Based on the terrace characteristics and dating, we found that tectonic uplift and river undercutting in the Wangcao Basin were more intensive than those in the Suiyang Basin. Actively driven by differential tectonic uplift and river erosion, the karst deep-cutting gorges and peak clusters landform is formed in the Furong River Basin, a part of Dalou Mountain, while the flat intermontane basins and hill clustered landform has been developed in the middle reaches of Wujiang River Basin.

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Geographical Study on COVID-19
Evolution pattern of scientific cooperation under several global major pandemics: Take SARS, H1N1, Ebola in West Africa and COVID-19 as examples
DUAN Dezhong
2021, 40 (1):  93-108.  doi: 10.11821/dlyj020200444
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International cooperation is not only the leading force for global exploration of cutting-edge science, but also the best way for global response to problems including resources and environment, climate change, health, public security and other issues. It takes only six months from the discovery of the Novel Coronavirus (COVID-19) to more than 6 million confirmed cases and 300,000 deaths, which not only proves that the COVID-19 is too contagious to be overcome, but also demonstrates the common destiny of all countries and regions in the era of globalization. In fact, when this outbreak was declared as a Public Health Emergency of International Concern (PHEIC) on 30 January 2020 by the WHO, international cooperation is regarded as the key to combating this pandemic. Based on the Web of Science database, this paper systematically reviews the international cooperation on scientific research and its evolution during several major global epidemics. The findings are as follows. In the international cooperation of SARS, H1N1 and Ebola, the United States has been playing a critical role. Meanwhile, Chinese Hong Kong and European countries took the lead in the research of SARS virus and Ebola virus, respectively. By intercepting the COVID-19 research papers on four time nodes, it is found that the cooperation between China and the United States is the constructive framework of the COVID-19 research international cooperation network. In view of the current global pandemic of COVID-19 virus, this article recommends that research institutions in China strengthen the research on COVID-19 virus and vaccines, and actively cooperate with foreign research institutions, especially those countries and regions with severe situations. In the direction of cooperation, the collaboration with U.S. research institutions should be strengthened. In terms of cooperation strategy, it can take advantage of the Hong Kong region to carry out tripartite or multi-party cooperation with relevant foreign research institutions.

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Articles
The construction of cyberspace elements hierarchical system based on man-land-network relationship
GUO Qiquan, GAO Chundong, SUN Kaifeng, CHEN Shuai, JIANG Dong, HAO Mengmeng
2021, 40 (1):  109-118.  doi: 10.11821/dlyj020200867
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As a common carrier of human and information, cyberspace is intertwined and integrated with geographical space. It has become a new spatial form of human activities as well as an important basis for the operation and development of social system. The diversity and volume of elements in cyberspace and the frequency and complexity of cyber-attacks have brought new challenges to the governance and security of cyberspace. At present, the cognition of cyberspace is inadequate, the geographical attributes of cyberspace are ignored, and a reasonable and complete classification framework of cyberspace elements has not been formed, making it difficult to meet the practical needs of cybersecurity business. Therefore, comprehensively considering both the interactions between cyberspace and geographical space and their characteristics, constructing a hierarchical system of cyberspace elements with all sorts of themes and clear layers, are of great importance for drawing geographic maps of cyberspace and realizing the visual expression of cyberspace. Based on the review of cyberspace hierarchical model, with cyberspace geography theory as guidance, focusing on the "man-land-network" relationship, combining with the practical demand for cybersecurity business, drawing on the construction method of geographic factor index system, the present study put forward a four-layer cyberspace hierarchical model including the geographical environment layer, the network environment layer, the behavior subject layer, and the business environment layer. Specifically, the geographical environment layer is the base layer, which is the carrier of all kinds of cyberspace infrastructure as well as the foundation of multi-source data integration, visualization, and comprehensive analysis; The upper layer is the network environment layer, including physical network and logical network. The behavior subject layer is composed of realistic roles, cyberspace roles, managers and organizations, and also involves their activities and social relations; The business environment layer is abstracted from the previous three layers, including all kinds of cybersecurity cases (incidents), critical network assets, security situation, cybersecurity protection activities, cybersecurity intelligence, and other elements related to cybersecurity business. Additionally, the methods to express and link the elements of each layer were also explored. All of these efforts could provide a scientific basis for the management of network asset and for the comprehensive prevention and control of cybersecurity.

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Spatial distribution of intra-product export trade of electronic machinery manufacturing products in China
LI Zhenfa, HE Canfei
2021, 40 (1):  119-137.  doi: 10.11821/dlyj020190854
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Electronic machinery manufacturing products have occupied a crucial position in trading activities of China and studying the spatial pattern of such products from the perspective of intra-product trade can help to understand the Chinese trading system better. After differentiating intermediate/final products and general/processing trading modes, this study analyzes the spatial distribution of enterprises in China exporting electronic machinery manufacturing products in the aspects of export places and trading partners, and explains the distribution based on the technological relatedness. The findings are as follows. As for the descriptive part, firstly, firms of the general trading mode are located in more cities than those trading processing products, in which the latter prefers to agglomerate in the eastern region. Similarly, firms exporting intermediate products are more scattered in the inner areas. Secondly, firms exporting intermediate products export to most of countries, while those with final products mainly concentrate in developing countries. In other words, developed countries, mainly in America and Europe, import more intermediate products from China. In addition, the firms with final products, particularly the ones under the general trading mode, tend to export more to the developing countries represented by those in Africa and South America. As for the empirical part based on econometric models, first of all, at the national level, for enterprises with intermediate products under both the general and processing modes, and the ones with final products under the general mode, the higher degree of their technological relatedness to the local product structure, the greater chances they come to this place to export. In the eastern region of China, such positive correlation also exists in firms with final products under the processing mode. When it comes to the central and western regions, this promoting effect of technological relatedness on exporting behaviors only exists in the general-trade enterprises. Next, for firms exporting products under the general mode, the higher degree of their technological relatedness to the product structure imported from China of a certain country, the easier they select the country as one of the trading partners. This relation is not robust for firms with products under the processing mode. Moreover, when dividing countries into different groups by income levels, such promoting effect is validated in general-trade firms exporting to countries of middle- and low-income groups, while it is insignificant in the high-income destinations.

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Evolution and mechanism of port hinterland in Yangtze River Delta
KANG Yizhi, HE Dan, GAO Peng, SUN Zhijing
2021, 40 (1):  138-151.  doi: 10.11821/dlyj020190853
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This study attempts to integrate the hinterland evolution of seaports and inland ports into a unified research framework. The field strength model is used to divide the direct hinterland scope of the main seaports and inland ports in the Yangtze River Delta (YRD) in 2001, 2008 and 2016. Afterward, this study analyzes the evolution characteristics, and summarizes the hinterland evolution influence mechanism of the two leading ports with the most significant evolution - Shanghai port and Ningbo port. The research outcomes reveal that: (1) There are significant differences in the comprehensive influence and traffic accessibility of each port, and there are also changes in their ranking. (2) Due to the port cluster of YRD involving seaports and inland ports, the high value areas of field strength are concentrated in Shanghai, Ningbo and Lianyungang ports. (3) Significant difference is found in the scope of direct hinterland, but the overall spatial pattern shows no great change. The most dramatic change is that the expanding hinterland scope of Ningbo port basically comes from the shrinking hinterland scope of Shanghai port. The potential reason is that the further expansion of Shanghai port is indirect hinterland of river-sea shipping rather than direct land hinterland. On the contrary, Ningbo port expands the direct land hinterland. (4) The endowment differences between two ports lead to different hinterland evolution mechanisms and various types of port groups. Limited by water depth, Shanghai port depends more on developed freight forwarding system, cross provincial strategic alliance, capital investment on inland ports along the Yangtze River and other market mechanisms. Furthermore, with the intergovernmental cooperation, tax relief and deregulation, Shanghai port gradually establishes a relatively loose port community, which strengthens the control of the source of goods and further expands the indirect hinterland based on river-sea shipping. (5) Ningbo port, with advantageous port resources, leans heavily on administrative power of Zhejiang provincial government to integrate the port resources in jurisdiction, which forms a relatively close port community. This action contributes to alleviating cargo flow saturation and improving traffic accessibility. In the meantime, Ningbo port gradually sets up the chain of dry port, by which it expands the direct land hinterland to Zhejiang jurisdiction.

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A review of agricultural landscape conservation pathways and its implications
YU Huirong, DU Pengfei
2021, 40 (1):  152-171.  doi: 10.11821/dlyj020190502
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Sustainable development of agricultural landscape is the cornerstone for ensuring food security, farming civilization, rural maintenance, eco-environmental security and even stable socioeconomic development. But the vulnerability of agricultural landscape calls for efficient landscape conservation to ensure its sustainability. That is typically the case in China: hyper urbanization and rapid economic development have highly risked the sustainability of agricultural landscape. Learning from the rich experience of developed countries in conserving agricultural landscape is urgently needed. As such, this paper makes a comprehensive review on the long-term pathways of agricultural landscape conservation in some typical developed countries like European countries, the USA and Japan, with the aims of exploring general pathways of agricultural landscape conservation, learning lessons from the experiences of developed countries and also providing some possible implications for agricultural landscape conservation in China.
The main results are as follows: (1) There are typically five agricultural landscape conservation patterns in the long-term pathways of developed countries’ agricultural landscape conservation. From ancient times to the present, many developed countries have gone through traditional-use of conservation pattern, exploitation conservation pattern, control conservation pattern, and governance conservation pattern to current stewardship conservation pattern. (2) We summarized the characteristics of each agricultural landscape conservation pattern. It was revealed that the goals of conservation patterns gradually transformed from ancient self-fed production to current sustainable development, with their landscape sustainability level first decreasing then rising. (3) We also identified that the pathway of agricultural landscape conservation in China generally kept consistent with the pathways of developed countries, that is, following the pathway of “traditional-use of conservation pattern→exploitation conservation pattern→control conservation pattern→governance conservation pattern→stewardship conservation pattern”. Nowadays, China is pursuing long-term sustainable development of agricultural landscape through the construction of Ecological Civilization System, which makes it somewhere in between governance conservation pattern and stewardship conservation pattern. (4) At the end of this paper, we proposed some possible implications and directions for the future agricultural landscape conservation in China, which include enhancing stakeholders’ awareness of landscape stewardship, optimizing multi-scale landscape patterns and services, securing information symmetry and communication channels, and improving policy resilience and efficiency.

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Field evapotranspiration experiment in Zhaoshu Island of Xisha Islands, South China Sea
HAN Shengsheng, LIU Suxia, SONG Xianfang, MO Xingguo, YANG Lihu, LI Daning
2021, 40 (1):  172-184.  doi: 10.11821/dlyj020190860
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Evapotranspiration is an important component of water balances on coral islands, which plays a pivotal role in the ecological protection of coral reefs. A field experiment using a self-made microlysimeter was carried out in Zhaoshu Island, Xisha Islands, China from June 20th, 2018 to August 16th, 2018, which obtained the change processes of actual evaporation after rainfall, as well as evapotranspiration characteristics of different underlying surface and calcareous sand particles. Soil on coral islands is mainly calcareous sand, which has high porosity and water binding capacity. The actual evaporation observation of sandy loam bare land showed that the average evaporation rate was 1.6±0.2 mm/d from the 2nd day to the 4th day after rainfall, which was followed by a rapid decrease on the 5th-7th days. Evaporation rate stabilized at 0.5±0.2 mm/d gradually after the 7th day. Soil water content took control of evaporation. The ratio of bare surface evaporation rate to pan evaporation rate had a significant linear correlation with surface soil water content, indicating that evaporation of bare land on coral islands could be predicted by pan evaporation and soil water content. Control evapotranspiration experiment showed that potential evapotranspiration rate of different types of microlysimeter followed a rule of ETgrassland in the open field > ETsandy loam in the open field > ETgrassland in forests belt > ETsandy loam in forests belt. The shade of forests could decrease evapotranspiration, however, evapotranspiration of grassland decreased larger than that of sandy loam soil under the forests belt. Evaporation of calcareous sand was affected by the sand textures, the larger the calcareous sand particles. The shorter the duration of rapid evaporation, and the smaller the evaporation rate. Daily evaporation rate (mm/d) and midday evaporation rate (mm/h) showed a significant linear correlation especially for sandy loam soil, fine sand, and medium sand. So, we could estimate daily evaporation of fine sand, medium sand, and sandy loam soil in South China Sea with midday evaporation rate for similar underlying surface and climate conditions.

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The effects of residential instability on migrants′ health in urban China
CHENG Hanbei, LIU Yuqi, TIAN Ming, LI Zhigang
2021, 40 (1):  185-198.  doi: 10.11821/dlyj020190815
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Health research has long recognized the importance of residential instability. However, less attention has been paid to disclose their relationships against the background of frequent mobility in urban China. Thus, this study used multilevel linear models and grouping regression to explore the impacts of residential instability on migrants′ health based on the data collected from a questionnaire survey involving 9 cities and 2573 respondents. The results were as follows: (1) Migrants in urban China exhibited an ordinary level of subjective well-being (SWB) but reported preferable value in self-rated physical health (SRH). Notably, there were significant differences in health between genders. (2) Migrants′ health was affected by sociodemography, residential instability, as well as geographical factors. For instance, migrants working overtime and those living in cities with higher housing prices exhibited lower health outcomes. Married, well-educated, and high-income migrants were happier than the rest of the migrants. No evidence has shown that marital status, education level, and monthly income were significantly related to their physical health. (3) Residential instability had a statistical significance in health outcomes, and the strength of effect varied in different gender groups. In detail, interurban and intraurban mobilities were negatively related to migrants′ health in both subjective well-being and physical health. Importantly, these relationships were prominent in terms of males. In other words, frequent mobility can reduce their health. Besides, migrants moving with family members and owning purchased houses exhibited better health than those moving on their own and living in rented houses, especially in female groups. Moreover, migrants residing in neighborhoods with a higher proportion of locals had a higher probability of reporting better health. This result was also obvious in female migrants who concerned more on neighborhood safety. Finally, the number of friends was positively correlated with migrants′ health, which implied the health promotion of social capital in cities. All in all, this study confirmed that residential instability had a significant impact on migrants′ health and that gender played a moderating role in this relationship. Men were more sensitive and vulnerable to mobility factors, while women′s poor health was attributed to housing and neighborhood instability. Therefore, we call for the government to strengthen the housing attainment, education, medical services, etc. to increase migrants′ settlement intentions and reduce the frequency of mobility. On the other hand, community committees should encourage migrants to interact with locals to build a cohesive and supportive neighborhood for health promotion.

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Examining the role of air quality in shaping the landscape of China′s internal migration: Phase characteristics, push and pull effects
CAO Guangzhong, LIU Jiajie, LIU Tao
2021, 40 (1):  199-212.  doi: 10.11821/dlyj020190892
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With the continuous changes in the composition and migration patterns of floating population in China, amenities such as air quality have gradually become important factors in shaping the spatial pattern of migration. On one hand, the heterogeneous demand structure of various subgroups of migrants is surely to lead to substantial change in their overall preference for attributes of destination cities as the composition of migrants evolves significantly in recent years, that is, but not limited to, the increasing shares of the high-skilled, the aged, and followers. On the other hand, emerging types of migration such as inter-city migration, secondary migration, and return migration has not only made the spatial modes of China′s internal migration much more complex than before but also provided more opportunities to cities that used to lack economic superiority and thus can rarely share the migration dividend in the past. Against this background, based on the data of population censuses and sample surveys since 2000 and by using panel data models, this paper explores the overall characteristics, changing trends and acting paths of the effect of air quality on migration. Regression results of the panel data model demonstrated the significantly positive association between air quality and net migration rate which has rarely been discussed in previous literature. A set of cross-sectional models further revealed the increasing role that air quality plays in affecting the geography of China′s internal migration, which is in line with the migration transition history of developed countries. In-depth analysis on the mechanism of this effect found that the environmental condition has been acting mainly as a push factor instead of a pull one. Air quality is directly related to the emigration decision, which means that a number of Chinese people have been escaping from heavily polluted areas. In contrast, satisfactory air quality and pleasant living conditions have not been a vital factor in attracting migrants. As it is a fact that income level and job opportunity still play a significant role in pulling, their overall influence has been shrinking gradually as the income level increases commonly in all Chinese cities. In addition, the study verified the guiding role of accessibility of educational resources for cities to attract internal migrants and further revealed the continuously strengthened position of megalopolises as the main spatial form of China′s new-type urbanization from the perspective of migration.

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Shrinking cities: Misunderstandings, identifications and reflections
WU Kang, QI Wei
2021, 40 (1):  213-229.  doi: 10.11821/dlyj020200359
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While China′s urbanization has been characterized by 'growth-oriented' development models, the recent literature has highlighted the emergence of urban shrinkage in China, i.e., cities and regions that endure sustained population losses. This is especially the case for some resource-based cities in Northeast and North China, which have been losing their population and suffering from stagnant and even negative local GDP growth. Shrinking cities is a new phenomenon for research in the areas of population-resources-environments, spatial planning and urban governance in China. Based on a brief review of related literature, this paper summarizes some misunderstandings in the research of shrinking cities in China. It is a challenge to identify shrinking cities scientifically because of different demographies, different classification standards and disconnection between attributes data and geographic units. Extending from the suggestion from Zhou and Shi (1995), this paper, based on urban physical areas comparison and urban administrative areas test, analyzes the changes of China′s urban population and proposes a framework to identify the shrinking cities. The results show that there are 114 designated cities, in which the population size of the "Chengrenkou" (residential population in the built-up area) in 2010 was smaller than that of the "Shirenkou" (residential population in the administrative area) in 2000. However, due to a larger "Shirenkou" size in 2000 in statistics than in actual situation, and also several inflated figures of "Chengrenkou" in 2010, the exact number of "shrinking cities" is less than 114. After excluding "urban administrative areas" with a larger rural population, 56 cities and 75 cities were in net outflow in 2000 and 2010, respectively. The results are highly policy-relevant, therefore we should adjust future policies regarding urban shrinkage management. Finally, this paper argues that China should establish the concept of urban physical areas and promote the regional collaborative statistical system of urbanization. And it is also necessary to build a "spatio-temporal aligned" geographic information system database of China's resident population and take the regional differences in the administrative divisions into account in order to continuously promote the accurate division of urban and rural population.

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Urban polycentric recognition and spatial interaction analysis based on word vector data field trajectory gravity
LI Xin
2021, 40 (1):  230-246.  doi: 10.11821/dlyj020190849
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Polycentric structure is an important method of dispersing urban population, relieving traffic congestion, adjusting the imbalance of job-housing, and dealing with "big city disease". First of all, word vector is used to describe the spatial characteristics and behavior rules of the trajectory big data, and vector operation is used to reflect the correlation between the origin points and destination points of the trajectories. In addition, the spatial grid of Zhengzhou city is divided, the gravity of grid units to mobile targets is measured by using the gravitational model of data field theory, and the recognition of polycentric structure is completed. At last, the interaction rules of the polycentric structure are explored with the assistance of the complex network theory, and the relationships between the polycentric nodes are reflected by the in-and-out intensity, net flow ratio and chain weight. The results show that: (1) The gravity strength of trajectories presents a circular spatial pattern with a strong core and weak peripheries, and the region with high gravity spreads along the main roads. There are significant differences in the unbalanced gravity of trajectories among the identified 21 centers. Urban elements and moving targets spread from the saturated core urban area to the periphery along the main traffic routes. The spatial distribution of polycentric structure presents a typical overflow pattern of dense inside and sparse outside. (2) The regional gravity intensity and interaction frequency of the peripheral sub-centers are low, and the interaction direction mainly goes towards the primary centers in the core urban area. Although the planning prospect of the peripheral centers is broad, due to the late planning, remote location and insufficient supporting facilities, their attraction to the surrounding areas is limited. And it will take a long time to achieve the planning objectives. In order to make the sub-centers decentralize better, it is necessary to strengthen the overall planning and guide the scientific development of the sub-centers. A polycentric structure recognition method and spatial interaction analysis method based on the trajectory gravity of word vector data field are proposed. The trajectory word vector describes the spatial information and travel pattern information in a comprehensive way, the trajectory gravity intensity expressed by the potential value of data field is more accurate, and the polycentric spatial interaction structure analyzed in a complex network is clearer. The evolution mechanism of polycentric structure is presented from the perspective of flow. This is a more suitable polycentric analysis method for trajectory data, which provides a new idea for urban planning.

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The spatial characteristics of railway passenger network in Russian capital cities based on the daily railway passenger flow
CHU Nanchen, ZHANG Pingyu, WU Xiangli, LI He
2021, 40 (1):  247-262.  doi: 10.11821/dlyj020190843
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This paper studied the spatial structure, pattern, and characteristics of Russian railway passenger network. The paper first built a daily railway passenger flow matrix consisting of 81*81 capital cities to evaluate the daily railway passenger flow of Russia. Then by analyzing the network density, three kinds of centralities, core/periphery structure and cohesive subgroups using the network analysis software - University of California at Irvine Network (UCINET), this paper displayed the structure and characteristics of Russian railway passenger network. Finally, the global trend analysis and spatial interpolation function of geographic information system (GIS) were used to simulate the pattern of the daily railway passenger flow and three kinds of centralities in Russia and to reveal the characteristics and the differentiation of their spatial distribution. The results are as follows. First, spatially, the railway passenger network of Russia is loosely organized, displaying the unbalanced characteristic of "dense in the west, while sparse in the east". The railway passenger network of different federal districts differs greatly as such: Privolzhsky (Volga) Federal District > Siberian Federal District > Central Federal District > Ural Federal District > North West Federal District > South Federal District > Far East Federal District> North-Caucasian Federal District. Particularly, the railway passenger connection density of the capital cities in the Central Federal District and along the trans-Siberian railway is higher than that of other capital cities in Russia. The railway subgroups and cores of the northern Europe clique, southern Europe clique, and Asia clique in Russia are different. Second, by analyzing the daily railway passenger flow, we find that the trans-Siberian railway line which has developed into the main "corridor" of Russian railway passenger flow is much higher than the rest lines. However, its south and north sides have shown an asymmetric reduction trend. And in the trans-Siberian railway line, Moscow, Yekaterinburg-Perm-Tyumen, Omsk, and Novosibirsk are located in the key positions of high railway passenger flow. Third, key elements related to railway such as population of the capital cities located on the southwest side of Russian population boundary (Saint Petersburg- Rupublic of Tuva) line is higher than that of the capital cities on the northeast side. Moscow, Saint Petersburg, Yekaterinburg, Tyumen, Rostov-on-Don, Krasnodar, Novosibirsk, and Tver are the national important railway passenger accessibility intermediary cities.

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Study on the spatial pattern and image of inbound tourists in the Pan-Yangtze River Delta
LU Shuying, TAO Zhuomin, LI Tao, PU Rong, RONG Huifang
2021, 40 (1):  263-278.  doi: 10.11821/dlyj020190801
Abstract ( 16 )   HTML ( 0 )   PDF (5107KB) ( 0 )  

City is an important space carrier for tourists' activities. Grasping the characteristics of tourists' mobility between cities is the premise and foundation for exploring the tourism links between regional cities, clarifying the mechanism of tourism-affected regional development and optimizing the layout and strategy of urban tourism development in the future. Based on the clustering method, mining algorithm and network analysis method, this paper takes geo-tagged photos as the research object, and analyzes the spatial characteristics of inbound tourists from 52 prefecture-level cities in the Pan-Yangtze River Delta from the perspectives of distribution, type, flow and image. Through the data acquisition, processing, analysis and other steps, some conclusions can be drawn as follows. The results show that according to the degree of inbound tourists, the study area can be divided into the inbound tourism core area, the sub-core area and the marginal area. The core area is highly consistent with the regional economic center, and higher economic level provides a strong support for the development of regional tourism. The sub-core area has prominent tourism resources, rich or special tourist resources can make up for development disadvantages and attract more tourists. The great tourism development potential of marginal area will become key development area in the future. At the same time, the density of inbound tourists' moving networks gradually decreases from the central core area to the outer edge area, forming a four-level network hierarchy, and the density of network structure decreases from east to west. Moreover, the distribution and flow of inbound tourists within the provinces and cities are also differentiated, which are closely related to resource endowments, economic levels, traffic conditions and service reception levels, and the different influencing factors have the difference function degree in different areas. Further quantitative analysis is needed at a later stage. Finally, the image analysis of inbound tourists shows that different regions generally have corresponding local characteristics, and confirm the influence and role of the most essential local characteristics of the destination on its spatial distribution and flow characteristics.

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Research on the process, characteristics and spatial effect of the development of Chengdu's museums
LIU Run, REN Xiaolei, YANG Yongchun, FENG Xiaofeng
2021, 40 (1):  279-291.  doi: 10.11821/dlyj020190802
Abstract ( 24 )   HTML ( 0 )   PDF (3486KB) ( 0 )  

Since the reform and opening-up, the institutional environment for the development of Chinese museums has undergone fundamental changes, from absolute government dominance to encouraging and supporting non-public capital to invest museums. Various social and market subjects have shown great enthusiasm and initiative in participating in the construction and development of museums. Domestic research has rarely systematically sorted out the development and characteristics of museums, and rarely explored the relationship between museum development and institutional environment. However, this work is of great significance for guiding museum development and enriching the theoretical connotation of museum research. Taking Chengdu, the city with the largest number of museums in China, as an example, and using qualitative methods such as semi-structured interviews, this paper systematically studies the development process, characteristics and spatial effects of museums in Chengdu. Results show that: (1) The museum development in Chengdu has experienced three stages, namely nationalization, non-nationalization and industrialization. The key features of museum development include the increasing number, various types, significant differences in the scale and level between state-owned and private nuseums, diverse functions, gradual formation of industrial foundation, and prominent relocation and agglomeration. (2) Institutional change has affected museum development by changing the types of participants and their perceptions and behaviors. Chengdu municipal government regards museums as an essential carrier for the development of cultural industries, and actively promotes the construction of state-owned museums and the gathering of private museums. Companies, which are market-oriented, try to use museums to demonstrate their social responsibility. Collectors and art workers, with strong individuality and subjectivity in their behavior, take museums as a platform for entrepreneurship and cultural creation. (3) The spatial effects of the development of state-owned museums in Chengdu are quite different from those of private ones. The former mainly refers to the influence of a single state-owned museum on the industrial type and land use of its surrounding area, and the latter mainly refers to the impact of the gathering of multiple private museums on the industrial and functional structure of the gathering area.

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