The high-speed rail network exerts a multifaceted influence on the spatial structure of urban agglomerations. While the reduced cost of regional factor flows has the potential to enhance overall economic efficiency, it also reinforces the advantages of central towns, leading to a “siphon effect” on surrounding small and medium-sized cities, exacerbating imbalances in urban development. The conventional “Land-use Transportation Interaction” theory, centered on location accessibility, falls short in explaining the intricate network effects of high-speed rail on urban agglomeration spatial structures. This article adopts an approach grounded in the “Space of Flows” paradigm, considering both “transfer” (exclusive of time and space, e.g., capital and labor) and “sharing” (non-exclusive of time and space, e.g., information and technology) effects of factor flows. It analyzes the cascading effects of the “high-speed rail network-factor transfer and sharing-urban agglomeration spatial structure”. Using Wuhan Urban Agglomeration as a case study, the research employs big spatial data (i.e., population migration) extracted from network location-based services to identify and measure factor transfer and sharing among cities and towns. Then, a set of spatial models and “What-if” analyses were applied to demonstrate the impact of the high-speed rail network on factor transfer, sharing, and the overall spatial structure of the urban agglomeration. The findings reveal a heterogeneous impact of high-speed rail development on the spatial structure of Wuhan Urban Agglomeration. The high-speed rail development propels labor transfer from surrounding small and medium-sized towns to central cities, creating a discernible polarizing effect on Wuhan’s economy, and presenting challenges to its neighboring cities’ economic development. Simultaneously, high-speed rail facilitates the dissemination of information and technology from central cities to peripheral areas, offering opportunities for regional economic transformation. This study overcomes the shortcomings of previous research, which have often oversimplified the interactions between cities. It established a unified analytical framework to explain the impact of the high-speed rail networks on the spatial structure of urban agglomerations.The research results aim to serve as a policy reference for optimizing the spatial structure of urban agglomerations.
During the process of regionalization in the last 20 years, inter-city co-construction zones have been undergone rapid expansion as well as vital and thorough reorganization, which profoundly reflects the cutting-edge orientation of the widespread economic and social restructuring and current regional process. Located in the developed eastern coastline areas in China, the Yangtze River Delta Region (YRDR) consists of a glocal city: Shanghai (municipality) and 3 rapidly developing provinces (Jiangsu, Zhejiang and Anhui). Driven by the global metropolis of Shanghai, the YRDR has developed into one of the world-famous city-regions, with the fastest economic and social development in China over the past forty years since the opening-up policy. In particular, establishing co-construction Zones, as one of the most important approaches to promote local economic competitiveness in the YRDR, has had a huge impact on the economic and social growth of the area. Since then, the YRDR has, in part, taken the approach that has been the most encouraging in establishing the co-construction zones. As a result, the YRDR’s inter-city co-construction zones have been dispersed across the province/municipality and even outside of it, with some of them turning into growth poles in the city-regions. Co-construction zones appear to have had a significant influence on the YRDR’s and the nation’s overall economic and social growth. The purpose of this paper is to explain how the multi-dimensional characteristics of scale, network, and territory shape the dynamics of restructuring and influence the formation, dilemma, and breakthrough of co-construction zones in the YRDR under the fluctuating external policy environment by referencing Jessop’s theoretical framework of “TPSN” and proposing a conceptual framework for changing regional city cooperation. The study finds that: 1) The co-construction zones’ complex features have been continually deconstructed and rearranged by the growing regional development shift, with capital orientation and crisis orientation acting as the main driving forces behind the evolution. Hence, the co-construction zones in the Yangtze River Delta Region have undergone three stages: An initial stage aimed at enterprise transfer, a transitional period of emerging dilemmas, and a new stage of new partnership agenda after 2016, displaying changing sociospatial relations under different capital demands and space fixs in response to institutional crises. 2) The scale, network, and territorial features of the zone were significantly influenced by the organization of shifting transitions from inter-governmental partnership to socionetwork action, as well as the more varied partner agenda. 3) Finally, the evolving course of sociospatial connections moves from a specialization advantage in a specific job to a comprehensive deployment system, indicating the significant trend of regional governance change under the increasing complex regional economic and social activities. The process of restructuring a co-construction zone involves changing sociospatial linkages, and its multidimensional features are continuously enhanced and updated in accordance with guidelines for social and economic growth.
Taking the “Carbon Peak” in 2030 as the research time point, the IPCC “bottom to up” method and social network analysis method are used to explore the network pattern of carbon emission and emission reduction potential of interregional urban agglomerations road logistics under different channel scenarios, and to analyze the influence of the Bohai Channel on it. The research shows that: 1) Differences in the carbon emission network of interregional urban agglomerations road logistics of different channel scenarios in 2030: Under the Land Channel scenario, the carbon exchange of interregional urban agglomerations is concentrated in the economic and traffic developed axes and the endpoint cities of the Bohai Strait; under the Land-Sea Channel scenario, the interregional carbon exchange is concentrated in cities adjacent to the Land Channel; The Bohai Channel improves the high energy consumption situation pointed by the “Bohai Strait endpoint cities” of the interregional urban agglomerations. 2) The network pattern of road logistics emission reduction potential in interregional urban agglomerations in 2030: with Dalian as the emission reduction pivot and the Bohai Strait as the center, strong emission reduction city pairs are more in the south than in the north, and there are zero emission reduction city pairs; The Bohai Channel mainly exerts carbon emission reduction influence on other cities through endpoint cities. However, its influence on the carbon emission reduction of some cities of far away from it and on the edge of road logistics is relatively limited.
As a special cross-regional major infrastructure, the operation of high-speed rail (HSR) reduces factor constraints faced by firms along the route, information asymmetry and agency costs among enterprises, promotes capital flows in the regions along the route, and influences inter-city investment. Several studies have explored the impacts on enterprises investment decisions of the introduction of HSR evaluated by a dummy variable reflecting whether a city is passed by HSR, however, little attention has been paid to the impacts of the improvement in accessibility and connectivity caused by HSR. To this end, this paper analyzes and evaluates the impact of the enhanced accessibility and connectivity caused by HSR on enterprises inter-city investment and its spatial heterogeneity, relying on data about the new investment decisions of Chinese listed companies from 2008―2017. It is found that: 1) Connectivity is improved higher in the cities in eastern region and accessibility is improved more significantly in the western region; the disparities of the accessibility and connectivity between mega-cities and small/medium-sized cities keeps widening. 2) The inter-city investment is mainly concentrated between cities in the eastern region and mega-cities, but the regional differences are narrowing. 3) The enhanced accessibility and connectivity caused by HSR have a significant positive impact on inter-city investment, and the impact of accessibility is greater than that of connectivity. 4) The impact of HSR accessibiity and connectivity on inter-city investment varies across different regions and cities with different population scales. Amongst, the improvement in connectivity has generated larger influence on the inter-city investment flowing to the cities in eastern region and mega-cities, while the enhanced accessibility significantly enhances the attraction of inter-city investment in cities of western region and small cities.
Submarine optical cables play a vital role in social economy development, and national defense and security. Submarine optical cables are always facing the risk of natural or man-made damage. However, the current researches of the vulnerability of submarine optical cable network are still limited to local network and national scale. In this article, we construct the global submarine optical cable network with information ports as nodes, and design a set of evaluation method combining complex network theory and simulation tools to analyze network vulnerability, classify hub information ports, and measure regional survivability in turn. The research results are as follows: 1) The submarine optical cable network has typical scale-free and small-world characteristics, and its vulnerability structure, which is not significant under random attacks but significant under deliberate attacks, is confirmed by simulation. In the deliberate attack mode, the submarine optical cable network is more sensitive to intermediary centrality attacks than point-degree centrality attacks, and it can be assumed that the transit and bridging functions of the information port are more critical to the vulnerability structure of the network. 2) The submarine optical cable network shows three states of “connectivity damage” “partial collapse”, and “complete collapse” in order with the increase of attack level. Accordingly, 66 hub information ports are identified and classified into 3 levels. The hub information ports appear the characteristic of polar core structure in the submarine optical cable network, and echo the main sea lanes, which are the main reasons for the vulnerability structure of the submarine optical cable network. Singapore, Cape Town, England’s west coast area, Florida and other information ports and their surrounding waters need to be focused on security. 3) The redundant connections of hub information ports make the submarine optical cable network have a certain self-regulation mechanism. However, the regional survivability levels vary greatly in space, specifically showing that Europe and North America have higher survivability levels, while East Asia, South Asia and South-Central Asia have midstream destructivity levels, Central America and North Asia have the lowest destructivity levels, and there is still much room for optimization. Overall, the research results can provide reference and decision support for the optimization of submarine optical cable network structure.
Based on the perspective of knowledge spillover costs and benefits, this paper deeply explores the U-shaped characteristics of the impact of changes in technological proximity between cities on knowledge spillovers. This paper first uses Chinese urban patent data and patent citation data to analyze the changes in technology proximity and knowledge spillover levels between Chinese cities from 2008 to 2017. It is found that the average technology proximity and knowledge spillover levels between cities during the review period show a fluctuating upward trend. The increase in knowledge spillover levels in Chinese cities is mainly due to the decrease in the number of city pairs with low knowledge spillover levels and the increase in the number of city pairs with medium-low knowledge spillover levels, showing a change in many city pairs from almost no knowledge spillover to a small amount of knowledge spillover. Among them, patent cross-referencing occurs most frequently among cities such as Beijing, Shanghai, and Shenzhen, and among cities in the Yangtze River Delta, the Pearl River Delta, and provincial capitals such as Wuhan, Changsha, and Chengdu. Patent cross-referencing between these cities and Beijing, Shanghai, and Shenzhen is also relatively frequent, forming a knowledge spillover concentration area with Beijing Shanghai Shenzhen as the core, including the Yangtze River Delta, Pearl River Delta, and provincial capitals. The improvement in technological proximity between Chinese cities from 2008 to 2017 is mainly due to the significant increase in the number of high-tech neighboring cities, which shows a moderate to high level change in technological proximity between some cities. Based on the current situation analysis, this paper selects China from 2007 to 2018 as a sample period to empirically test the impact and mechanism of changes in technological proximity between cities on knowledge spillovers. The research results show that the level of technological proximity and knowledge spillovers between cities presents a U-shaped feature, that is, higher and lower technological proximity between cities contribute to promoting the occurrence of knowledge spillovers, However, there is less knowledge spillover between cities with medium technology proximity, resulting in medium technology proximity traps. Mechanism research has found that specialized technological exchange and cooperation between cities with high technological proximity can generate explicit economies of scale, and cities can better understand, learn, and utilize each other’s spillover knowledge, enhance the benefits of knowledge spillovers, and reduce the cost of knowledge spillovers. Differentiated technology exchange and cooperation between cities with lower technological proximity can generate scope economic benefits, without spending a lot of effort on information screening during the communication process. Knowledge spillover benefits are high and costs are low, thereby stimulating knowledge spillovers between cities. Relatively speaking, knowledge spillover benefits between cities with medium technology proximity are lower, and there are higher costs. The research conclusions of this article not only help clarify the relationship between technology proximity and knowledge spillovers, further expand the relevant research literature in this field, but also provide beneficial insights for effectively promoting collaborative innovation between cities and accelerating the construction of national innovation systems.
The life course events of migrants are important practices in daily life, and their impact on migrants is related to the vital interests of migrants and the sustainable development of urbanization. Using the data of China Migrants Dynamic Survey in 2018 (absence of data Hong Kong, Macao and Taiwan), migrants’ settlement intention was measured, and binary logistic regression models was established to explore the impact mechanism. The life course events in each stage of the life cycle of migrants will trigger their thoughts on whether to stay or leave in the receiving cities. The main findings are as follows: 1) The proportion of migrants who intend to stay in the receiving cities is 85.10% and the probability of re-migration in a shorter period of time is low. 78.39% migrants who intent to stay in the receiving cities intend to stay for a long time and there are significant differences among cities. 2) Graduation makes migrants tend to stay for a short period of time. Having children in the receiving city and children’s age near to primary or junior high school age significantly increase the probability of migrants’ settlement or long-term settlement intention. The deterioration of physical condition could increase settlement intention but have no significant impact on their long-term settlement. Marriage, losing job and retirement could increase migrants’ long-term settlement intention by the effects from characteristics of families or individuals. 3) Migrants’ characteristics of demography, family, migration and cities’ features have different effects on migrants’ settlement intention or long-term settlement intention. Finally, suggestions for high-quality urbanization of migrants are put forward in terms of housing, fertility, health, and education, including creating long-term job opportunities and living conditions for professional and skilled talents; improving policies on public rental houses and co-ownership houses to reduce the cost of marriage for migrants; popularizing cities’ public healthcare and health services; granting equal educational rights to migrant children, and creatiing an elderly friendly city.
The global economy is undergoing a transition between old and new drivers, with digital trade being a typical characteristic of the current economic structural transformation. In the process of the vigorous development of the digital economy, the field of digital trade has shown strong competitiveness. Compared with traditional trade, it has stronger resilience and can withstand the downward pressure of the global economy. This study utilizes trade data from the OECD database spanning 2008 to 2019, selecting 6 highly digitized industries, to explore the evolution of the global digital trade from both network structure and influencing factors perspectives. The study found that: 1) The spatial distribution of global digital trade is uneven, with major trade nodes and connections concentrated in the Western and Northern Hemispheres. “USA, Japan, and Europe” as leaders in the global digital economy and digital trade play crucial roles in the global digital trade network. 2) Different industries exhibit varying structure and density in digital trade networks. Except for the financial services trade network, which is a polycentric structure, trade networks of other industries are all single-center structures with the United States as the core. China occupies a peripheral position in the digital trade networks of the 6 industries. 3) Information and communication technology, openness level, internet penetration, income levels, currency, language, and regional trade agreements all contribute to the enhancement of bilateral trade flows. Bordering relationship is favorable for boosting trade flows only in the early stages, and religious culture has no significant impact on digital trade. Geographical distance still significantly inhibits digital trade, challenging the notion that “distance is dead”. This study aims to explore the spatial distribution and evolution of global digital trade, in order to enhance China’s radiative capacity in the global digital trade network and seek competitive advantages.
Food security is a complicated social and economic issue, linked to social stability and physical health, which is always a key concern for governments and academia around the world. This study reviewed the evolution and characteristics of the concept of food security, analyzed the main measurement indicators and the advantages and disadvantages of scenario analysis methods of food security in recent years, and explored the possible research directions of geography in food security systems. The main conclusions are as follows: 1) The concept of food security has developed into a comprehensive concept with 4 dimensions and 5 scales. The 4 research dimensions of food security are food availability, access, utilization, and stability, and 5 scales are the individual, household, national, regional and global levels. 2) Households are the basic production and living unit of society, and the country shoulders responsibility for safeguarding food security of the whole society. So food security at household and national levels should be focus of the food security assessment. The attention of academic and the governments has also shifted from national scale to household and individual scale. Nutrient supply and dietary bulk have become key indicators for measuring food security. 3) At present, there are more than 200 definitions of food security and more than 450 measurement indicators in the world. Most of food security assessment indicators have some shortages, such as insufficient quantification, non-uniform standards, inaccurate data, etc. There is no global standardized assessment indicator system covering the 4 dimensions. Large scale inaccurate and incomplete data sets have become one of the biggest obstacles in food security assessment. 4) Computable General Equilibrium (CGE) model or Partial Equilibrium Theory (PE) are used to predict the situation of food security. There are significant differences in the prediction results of different studies on future food security. The accuracy of the forecast results is difficult to measure, too. 5) Food security is a comprehensive and complex system, involving a series of processes such as agricultural production, supply chain, household food access, food security evaluation, and coping strategies, etc. Geography, characterized by comprehensiveness and regionalism, can make important contribution to the studies of driving forces of food supply, food supply chain, food security assessment indictor system, coping strategies, etc.
Tourism urbanization is a new form of urbanization. Under the support of national strategies such as beautiful China and ecological civilization and people’s expectations for better human settlements, a scientific assessment of the coupling coordination and driving force of tourism urbanization and human settlements in the western China is of great significance for the development of green and low-carbon economy and the construction of livable, pleasant and tourable cities. However, existing studies on the bidirectional relationship between tourism urbanization and human settlements are still lacking, especially from the perspective of spatial correlation. On the basis of constructing the theoretical framework of coupling coordination between tourism urbanization and human settlements, this paper empirically analyzes the coupling coordination and driving force between tourism urbanization and human settlements in the western China from 2005 to 2019 by means of coupling coordination model, spatial gravity model and geographical detector. The results show that: 1) The average value of the comprehensive index of tourism urbanization and human settlement environment is on the rise, the development level of tourism urbanization is faster than that of human settlement environment, but the index of human settlement environment is higher than that of tourism urbanization. 2) The intermediate coordination regions of the coupling coordination degree of tourism urbanization and human settlements are mostly, which have evolved into high-level coordination after 2017, and the coupling coordination type has gradually changed from the lagging type of tourism industry to the synchronous development type. 3) The spatial trend of the coupling coordination degree between tourism urbanization and human settlements is extremely unbalanced, and the spatial linkage intensity shows a chain-like spatial correlation pattern with Ningxia, Shaanxi, Chongqing and Guizhou as the main axis. 4) The difference of coupling coordination degree is the result of the combined action of different driving factors. International tourism income is the dominant driving force, per capita social fixed asset investment is the fundamental driving force, and the number of A-level scenic spots is the original driving force, among which the interaction between international tourism income and A-level scenic spots has the strongest explanatory power. Therefore, special attention should be paid to the interaction between international tourism income and A-level scenic spots when formulating the coupling and coordinated development strategy of tourism urbanization and human settlements in the western China. This paper focuses on the spatio-temporal coupling coordination and driving force between tourism urbanization and human settlements in the underdeveloped the western region of China, constructs its theoretical framework and innovatively adds the analysis and discussion of the coupling coordination spatial linkage. On the one hand, this paper provides a new idea for scientific breakthroughs in the interdisciplinary fields of tourism geography and human settlement environment, and on the other hand, it provides a new inspiration for the coupling and coordination of tourism urbanization and human settlement environment in western China.
This article takes Dongning in Heilongjiang Province and Hunchun in Jilin Province as research cases, constructs a comprehensive index system for sustainable urbanization development of border cities from three dimensions of urban economy, port economy and social condition, using the entropy method and the modified McKinsey Matrix to evaluate the level of urbanization development and the comprehensive performance and trends in sustainable urbanization of border cities, and finally exploring the main obstacle factors that affect sustainable urbanization development through the obstacle degree model. The results show that: 1) The overall level of urbanization development in Dongning and Hunchun shows an upward trend, which is mainly influenced by the development level of urban economy and port economy. 2) The overall trend of sustainable urbanization in Dongning and Hunchun is synchronized with its urbanization development process, and has generally experienced 3 stages of sustainable development with low development level (1993—2005), non-sustainable development with continuous improvement of development level (2006—2016), and sustainable development with medium development level (2017—2020). 3) The sustainable development of urbanization in Dongning and Hunchun has the same general trend, but shows some different characteristics at some stages due to the port’s economy development level. 4) Urban economy is the main obstacle standard layer that affects the sustainable urbanization development of Dongning and Hunchun in the long term, total investment in fixed assets, general public budget expenditure, general public budget revenue and export dependence are the main obstacle factors. The results of this article can provide some theoretical and empirical references for the study of sustainable urbanization in border cities.
Urban green spaces are one of the essential infrastructure elements for promoting the rational allocation of spatial resources. Taking the completed affordable housing in Guangzhou City as the research object, the study employs GIS network analysis to analyze the accessibility of residents living in affordable housing to green spaces of different scales and levels using various transportation modes. Research findings: 1) The accessibility of affordable housing residents to district-level and street-level green spaces is less influenced by transportation modes. 2) The distribution differences between green spaces and affordable housing were verified using kernel density analysis and standard deviation ellipse analysis. The results indicated that green spaces around affordable housing had limited coverage, and the accessibility to green spaces of various levels was relatively poor. The development direction of affordable housing did not align with the planning direction of green spaces, resulting in affordable housing being situated at the periphery of green areas. 3) The accessibility of green spaces is higher for the combination of subway and bus or car compared to the combination of subway and walking. This is mainly because green spaces are typically located farther from the city center or busy areas, and subway, bus, or car modes can cover longer distances. The results of this study provide valuable insights for Guangzhou City’s efforts in building new affordable housing during the “14th Five-Year Plan” and can contribute to optimizing the urban spatial layout.
The evolution of rural tourism destinations is dynamic and complex due to the interaction of multiple factors. From the perspective of social-ecosystem resilience, revealing the complex evolution law of rural tourism destinations can provide theoretical support for effectively promoting rural revitalization. Based on adaptive cycle theory and core-edge theory, this paper uses multiple integration methods such as set pair analysis, vector autoregression and system dynamics simulation to compare and analyze the evolution mechanism and path differences of social-ecosystem resilience in the core-edge rural tourism destinations. The results show that: 1) Tourism can promote the integrated and balanced development of the resilience of the core-edge rural tourism destinations, and the resilience gap shows a decreasing trend. 2) Besides, the resilience system of the core-edge rural tourism destinations has complex interaction and coordinated orderly development. The resilience of the social, economic and ecological subsystems is a nonlinear dynamic causal relationship with each other. Under the action of this nonlinear complex self-organizing force, the coupling and coordination degree between the subsystems shows a good development trend. 3) Furthermore, under the multi-scenario simulation of complex systems, coordinated development or ecological protection is the appropriate development path for rural tourism destinations in core areas, while tourism priority is the appropriate development path for rural tourism destinations in edge areas. 4) Finally, there are differences in the factor systems driving the resilience evolution of the core-edge rural tourism destinations. At the system level, the ecological system has the highest impact on the resilience in the core areas, while the social system has the highest impact on the resilience in the edge areas. At the factor level, ecological factors are the common factors affecting core-edge rural tourism destinations. The core area can improve the ecological resilience through ecological restoration, and the edge area can transform the ecological advantages into development advantages, thus significantly improving the resilience of rural tourism destinations.
The ecological environment serves as the core of intangible cultural heritage (ICH), providing vital resources for its preservation and transmission. While substantial research has been conducted, the environmental support behind intangible cultural heritage and the nurturing role of the habitat in the formation of ICH have not been thoroughly explored and understood. Research on the ecological response of ICH can furnish new insights and approaches for exploring cultural ecology, preserving the human-environment relationship, and clarifying socio-ecological networks. This study focuses on ethnic cultural and ecological protection area of Southeast Guizhou, leveraging geographic spatial analysis methods and linear diffusion continuity analysis to the integral role of ecological factors in supporting the preservation and development of ICH. The key findings are as follows: 1) ICH distribution in Southeast Guizhou exhibits a preference for mountainous and aquatic environments, and the degree of ecological response differs among the various ICH within the three areas, revealing distinct sub-cultural-ecological systems within the broader region. 2) The environmental dependence of ICH varies among different cultural types, with production, construction, medicine, manufacturing, and food and beverage brewing showing the most pronounced ecological dependence. Notably, Some folk customs may not directly depend on environmental elements. However, their indirect reliance on the environment becomes evident when considering their association with other ICHs that are environmentally dependent. Additionally, some folk activities inherently carry connotations of nature worship. 3) ICH has a certain degree of ecological vulnerability. Biodiversity loss, soil erosion, water pollution, and climate change pose significant threats, particularly for those directly depending on environmental and biological resources. 4) Due to its ecological impact, ICH plays an instrumental role in constructing and maintaining local environmental order, as manifested by its promotion of cross-county, cross-altitude, and cross-terrain division of labor and cooperation, thereby positively bolstering ethnic exchanges. This suggests that the establishment of social order, division of labor, and societal norms cannot be decoupled from the maintenance of a foundational environmental order. ICH, therefore, serves as a mediator between environmental and social order. Given these insights, it becomes evident that ICH protection should not isolate it from other cultural phenomena or simply regard it as an independent commodity for packaging and development. Instead, it’s essential to fully comprehend the “cultural-ecological-societal” network that revolves around ICH, further discern its degree of environmental dependence, and harness its environmental order function. Doing so will provide a solid scientific basis for promoting the construction of cultural and ecological protection areas.
To analyze the sources and spatial distribution of net anthropogenic nitrogen input (NANI) and net anthropogenic phosphorus input (NAPI) in China, this study constructed regional the NANI and NAPI models for 367 urban units in China in 2020. The study utilized standard deviational ellipse and Local Moran's Index for spatial heterogeneity analysis. In addition, this study also conducted 10000 Monte Carlo simulations on the model parameters to analyze the uncertainty of the model. The main conclusions are as follows: 1) In 2020, the NANI and NAPI in mainland China were 4596.43 kg N/(km2·a) and 840.02 kg P/(km2·a) respectively; 2) The application of chemical fertilizers was the primary contributor to NANI and NAPI, with 80.93% and 89.65% of the urban units being their largest contributors, respectively; 3) The spatial distribution of NANI and NAPI in China exhibits significant clustering and heterogeneity. The areas to the southeast of the Hu huanyong Line have notably higher NANI and NAPI compared to the northwest, with aggregation mainly occurring in the North China Plain region. 4) When the coefficient of variation of the parameters is 30%, the average relative errors of NANI and NAPI are 7.3% and 13.6%, respectively, indicating good simulation results. The NANI and NAPI models serve as quantitative tools for assessing the nitrogen and phosphorus emission status in a region, providing technical support for the identification and management of nitrogen and phosphorus pollution in key areas of China.
This study explores two limiting factors of long-term high-resolution agricultural harvest sequences reconstruction based on gazetteers. The first one is the interference caused by the coexistence of good and poor harvest records in the spatiotemporal distribution in the gazetteers. This study defines this phenomenon as “good and bad harvests combination”, and preliminarily analyzes its possible causes. This second limiting factor caused by the asymmetry of missing records of good and bad harvests is also analyzed. This study effectively overcomes these limitations by introducing non-linear assignment of crop yield levels and interannual decay indices, and proposes a new reconstruction method for regional agricultural harvest sequences, which could: 1) Extend the reconstruction time scale to a large extent while maintaining annual resolution; 2) Integrate the phenomena of harvest and failure into the same sequence into the same sequence. The method was applied to four sub-regions in Shanxi and Shaanxi during the Ming and Qing dynasties. The results show that: 1) The agricultural harvest in Shanxi and Shaanxi shows two fluctuation patterns: low-frequency high-amplitude pulses with a quasi cycle of about 40 years and high-frequency low amplitude oscillations; 2) There is a good correspondence between the agricultural harvest in Shanxi and Shaanxi and climate factors, which is “negative during cold and positive during warm” and “negative during dry and positive during humid”; 3) The “pulse” “adaptive”, and “periodic” response patterns of the social system to climate change are reflected in the agricultural harvest sequence in Shanxi and Shaanxi during the Ming and Qing dynasties: Severe crop failures periodically impacted local society, while the majority of other periods were characterized by high-frequency minor crop failure fluctuations. Both types of crop failures significantly decreased in the 18th century, which is consistent with the significant population growth in this area and the “prosperous era from Kangxi Reign to Qianlong Reign” recorded by historians.
High latitude permafrost regions are the most sensitive areas to climate change. The degradation of permafrost seriously affects the soil carbon cycling process. Revealing the vertical distribution pattern of soil organic carbon in permafrost layers under different land cover types is of great significance for predicting future changes in soil carbon pools in permafrost regions. Here we select forests, forest swamps, and shrub swamps in the high latitude permafrost areas of the Da Hinggan Mountains. Soil columns (7-8 m) were collected using drilling methods to measure soil carbon (organic carbon, soluble organic carbon) under the three different land types, and further analyzed the carbon content at different depths. The results showed that as the depth increased, the soil carbon contents decreased, and the organic carbon content varied from14.55 g/kg to 95.98 g/kg (forest swamp), from 17.48 g/kg to 132.93 g/kg (forest), and from 2.58 g/kg to 396.50 g/kg (shrub swamp). There was also a high carbon content soil layer in permafrost layers. The average content of organic carbon and soluble organic carbon in the active layer soil is as follows: shrub swamp>forest>forest swamp, and the average content of organic carbon and soluble organic carbon in the permafrost layer soil is as follows: forest swamp>forest>shrub swamp. The correlation analysis revealed significant negative correlations between depth and soil organic carbon content, water-soluble organic carbon content, and soil water content in soils under forest and shrub swamp conditions. However, there was no significant correlation between depth and these indices in soils under forest swamp conditions. Additionally, pH values were significantly positively correlated with depth across all soils, while they were negatively correlated with soil organic carbon content, soluble organic carbon content, and soil water content. The coefficient of variation of organic carbon in the active layer is 30.31%-114.26%, and the coefficient of variation of organic carbon in the permafrost layer is 30.23%-192.09%. Correlation analysis showed that soil organic carbon was negatively correlated with depth and pH, and significantly positively correlated with soil moisture.
With a focus on the Medieval Warm Period (MWP) and the Little Ice Age (LIA), the last millennium is a crucial period in the study of global climate change. In this study, a sediment core (SCH17-04) was collected from Shuangchi Maar Lake, Hainan Island, South China, and its n-alkanes proxies, including the ratios of Tree/Grass, Proportion of aquatic (Paq), Carbon Preference Index (CPI) and Average Chain Length (ACL) were determined. Based on the analysis of Accelerator Mass Spectrometry (AMS) 14C age and n-alkanes, the climatic and environmental characteristics of this region were reconstructed from 775 to 1550. The results showed that the proportion of long-chain n-alkanes was relatively high, while the proportion of medium- and short-chain n-alkanes was relatively low, suggesting that the organic matter inputs to the sediments of Shuangchi Maar Lake over the last millennium were mainly dominated by terrestrial higher plants, with relatively small contributions from aquatic plants and fungi and algae. Based on the above indicators, the environmental changes of Shuangchi Maar Lake over the past millennium can be divided into three stages: 1) In the late Dark Ages Cold Period, the gradual decrease in the Tree/Grass ratio and the significant increase in the ACL value indicated a gradual decrease in woody plants in the study area, indicating that the climatic environment of the study area was drier during this period. 2) In the Medieval Warm Period, low Tree/Grass values and high ACL values indicated an increase in the proportion of herbaceous plants and a relative decrease in the proportion of woody plants in the study area, suggesting a drier climate during this period. 3) In the early Little Ice Age, the increase in Tree/Grass values and decrease in ACL values indicated a gradual increase in the proportion of woody vegetation and a gradual decrease in the proportion of herbaceous vegetation, indicating a wetter climate during this period. In addition, the n-alkane records of Shuangchi Maar Lake were consistent with other climate records revealed by the lacustrine sediments of Huguangyan Maar Lake in the northern Leizhou Peninsula, Dongdao Island in the Xisha Islands, and stalagmite records from Thailand, etc., indicating a relatively dry climate condition during the Medieval Warm Period. Furthermore, it was found that during the Medieval Warm Period (Little Ice Age), the drier (wetter) climatic characteristics of the tropical northern margin could be related to the northward (southward) migration of the Intertropical Convergence Zone, the expansion (contraction) of the tropical rainbands, and the decrease (increase) of the sea surface temperature gradient in the eastern and western Pacific, respectively.
