2020 Vol. 30, No. 6
Display Method:
2020, 30(6): 947-958.
doi: 10.1007/s11769-020-1157-5
Abstract:
The rapid development of China's economy and urbanization has given rise to noticeable environmental problems, among which the change of air quality has received extensive attention. The panel data of PM2.5 (particles with an aerodynamic diameter of 2.5 μm or less) in 343 prefecture-level cities in China from 1998 to 2016 were statistically analyzed to reveal the characteristics of the temporal evolution and spatial variation of China's air quality in the past two decades. The results show that: 1) the overall deterioration trend of air quality is obvious throughout the country. The variation trend of PM2.5 was divided into three phases: rapid-growth phase (1998–2007), lag phase (2006–2011) and mildly-incremental phase (2012–2016), with their average growth rates of 7.19%, −3.59% and 0.52%, respectively. 2) The spatial difference of PM2.5 values in China increased significantly with time. Since 2003, the high-value area in the east has expanded rapidly, and polarization became much more pronounced. The change rate of PM2.5 is high in the east and west and low in the middle. The change rates of most areas in the west exceed more than 80%, and in the east lie somewhere between 40% and 60%. In the midlands, the change rate is not large and some regions even show a negative growth. 3) The change rate of PM2.5 is also high in areas with higher values. However, in regions where the change rate of PM2.5 is high, the value of PM2.5 is not always high. The high change rate is mainly attributable to the low base value of PM2.5 and the cities concerned belong to sensitive areas. 4) According to the PM2.5 warning index, the number of strong, medium, weak and non-warning areas in China is 45, 85, 159 and 54, respectively.
The rapid development of China's economy and urbanization has given rise to noticeable environmental problems, among which the change of air quality has received extensive attention. The panel data of PM2.5 (particles with an aerodynamic diameter of 2.5 μm or less) in 343 prefecture-level cities in China from 1998 to 2016 were statistically analyzed to reveal the characteristics of the temporal evolution and spatial variation of China's air quality in the past two decades. The results show that: 1) the overall deterioration trend of air quality is obvious throughout the country. The variation trend of PM2.5 was divided into three phases: rapid-growth phase (1998–2007), lag phase (2006–2011) and mildly-incremental phase (2012–2016), with their average growth rates of 7.19%, −3.59% and 0.52%, respectively. 2) The spatial difference of PM2.5 values in China increased significantly with time. Since 2003, the high-value area in the east has expanded rapidly, and polarization became much more pronounced. The change rate of PM2.5 is high in the east and west and low in the middle. The change rates of most areas in the west exceed more than 80%, and in the east lie somewhere between 40% and 60%. In the midlands, the change rate is not large and some regions even show a negative growth. 3) The change rate of PM2.5 is also high in areas with higher values. However, in regions where the change rate of PM2.5 is high, the value of PM2.5 is not always high. The high change rate is mainly attributable to the low base value of PM2.5 and the cities concerned belong to sensitive areas. 4) According to the PM2.5 warning index, the number of strong, medium, weak and non-warning areas in China is 45, 85, 159 and 54, respectively.
2020, 30(6): 959-975.
doi: 10.1007/s11769-020-1161-9
Abstract:
Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative, and remarkable progress has been made since 2013. Taking the 65 countries along the Belt and Road (BRI countries) as the research areas and using collaborated Web of Science (WOS) core collection papers to construct an international scientific collaboration matrix, the paper explores the spatial structure, hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road. The results show that: 1) Beyond the Belt and Road regions (BRI regions), Central & Eastern Europe, China and West Asia & North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions. China has the dominant role over other BRI countries in generating scientific links. The overall spatial structure has changed to a skeleton structure consisting of many dense regions, such as Europe, North America, East Asia and Oceania. 2) Within the Belt and Road regions, Central & Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries. The spatial structure of scientific collaboration networks has transformed from the ‘dual core’ composed of China and the Central & Eastern Europe region, to the ‘multi-polarization’ composed of ‘one zone and multi-points’. 3) The hierarchical structure of scientific collaboration networks presents a typical ‘core-periphery’ structure, and changes from ‘single core’ to ‘double cores’. 4) Among the formation mechanisms of scientific collaboration networks, scientific research strength and social proximity play the most important roles, while geographical distance gradually weakens the hindrance to scientific collaboration.
Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative, and remarkable progress has been made since 2013. Taking the 65 countries along the Belt and Road (BRI countries) as the research areas and using collaborated Web of Science (WOS) core collection papers to construct an international scientific collaboration matrix, the paper explores the spatial structure, hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road. The results show that: 1) Beyond the Belt and Road regions (BRI regions), Central & Eastern Europe, China and West Asia & North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions. China has the dominant role over other BRI countries in generating scientific links. The overall spatial structure has changed to a skeleton structure consisting of many dense regions, such as Europe, North America, East Asia and Oceania. 2) Within the Belt and Road regions, Central & Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries. The spatial structure of scientific collaboration networks has transformed from the ‘dual core’ composed of China and the Central & Eastern Europe region, to the ‘multi-polarization’ composed of ‘one zone and multi-points’. 3) The hierarchical structure of scientific collaboration networks presents a typical ‘core-periphery’ structure, and changes from ‘single core’ to ‘double cores’. 4) Among the formation mechanisms of scientific collaboration networks, scientific research strength and social proximity play the most important roles, while geographical distance gradually weakens the hindrance to scientific collaboration.
2020, 30(6): 976-992.
doi: 10.1007/s11769-020-1158-4
Abstract:
The core issue of sustainable development refers to the coordinated development of economic-social-environmental issues. In the present study, by complying with the China Sustainable Development Indicator System (CSDIS) concept, a comprehensive index system was built; besides, Natural Breaks (Jenks) Classification Method, Exploratory Spatial Data Analysis and Geographic Detector Analysis were conducted to delve into the sustainability and coordinated degree at city level in China from 2007 to 2017. The achieved results are presented as follows. First, for spatial differentiation, the overall spatial distribution pattern was characterized by the high-value units in eastern China and the low-value units in western China from 2007 to 2017. To be specific, the high-value units were radiated along the Beijing-Guangdong Axis (Jing-Guang Axis) centered on the core of Beijing-Tianjin-Hebei Region, the middle-value units were distributed in strips along the coast, and the low-value units were vastly gathered in western China and gradually break via the Hu Huanyong line (Hu Line) in south China from 2007 to 2017. More specifically, based on the five subsystems, the pattern of each system was consistent with the whole, whereas the degree of concentration was different. Second, for spatial correlation, the significant High-High (HH) areas were primarily distributed in the core of Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions. The significant Low-Low (LL) areas were continuously distributed in the southwest China and broke through the Hu Line from 2007 to 2017. There were insufficient number of significant High-Low (HL) and significant Low-High (LH) areas, whereas the spatial agglomeration of them was less obvious. Third, for internal coupling coordination, the spatial differentiation between the coupling degree and the coupling coordinated degree was significantly consistent in 2007 and 2017. The Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions have demonstrated a high level of coordinated evolution, and the pattern of western mountainous areas exhibited a low degree of coordinated growth. Lastly, based on the combination of quantitative and qualitative, its factors were underpinned by robust economic strength, the vitality support of the information level and the basic support function of the topography, active guidance of national policies and path dependence and industrial transfer.
The core issue of sustainable development refers to the coordinated development of economic-social-environmental issues. In the present study, by complying with the China Sustainable Development Indicator System (CSDIS) concept, a comprehensive index system was built; besides, Natural Breaks (Jenks) Classification Method, Exploratory Spatial Data Analysis and Geographic Detector Analysis were conducted to delve into the sustainability and coordinated degree at city level in China from 2007 to 2017. The achieved results are presented as follows. First, for spatial differentiation, the overall spatial distribution pattern was characterized by the high-value units in eastern China and the low-value units in western China from 2007 to 2017. To be specific, the high-value units were radiated along the Beijing-Guangdong Axis (Jing-Guang Axis) centered on the core of Beijing-Tianjin-Hebei Region, the middle-value units were distributed in strips along the coast, and the low-value units were vastly gathered in western China and gradually break via the Hu Huanyong line (Hu Line) in south China from 2007 to 2017. More specifically, based on the five subsystems, the pattern of each system was consistent with the whole, whereas the degree of concentration was different. Second, for spatial correlation, the significant High-High (HH) areas were primarily distributed in the core of Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions. The significant Low-Low (LL) areas were continuously distributed in the southwest China and broke through the Hu Line from 2007 to 2017. There were insufficient number of significant High-Low (HL) and significant Low-High (LH) areas, whereas the spatial agglomeration of them was less obvious. Third, for internal coupling coordination, the spatial differentiation between the coupling degree and the coupling coordinated degree was significantly consistent in 2007 and 2017. The Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions have demonstrated a high level of coordinated evolution, and the pattern of western mountainous areas exhibited a low degree of coordinated growth. Lastly, based on the combination of quantitative and qualitative, its factors were underpinned by robust economic strength, the vitality support of the information level and the basic support function of the topography, active guidance of national policies and path dependence and industrial transfer.
2020, 30(6): 993-1004.
doi: 10.1007/s11769-020-1162-8
Abstract:
Understanding the spatiotemporal patterns of three-dimensional urban forms, especially building height, can have important implications for improving urban air quality and mitigating the urban heat island effect by optimizing urban planning and management policies. This study investigated building height evolution and its influencing factors over approximately half a century (1960–2017) in Guangzhou, China. The results indicated that the logarithmic declines in height, quantity, and area of urban buildings followed Zapf's law, which restricts the three-dimensional shape of the urban form. The urban building height decreased from the center to the periphery of the city and decreased with decreasing altitude and increasing distance from main roads. These characteristics constituted the three main spatial differentiation rules of building height in the central district of Guangzhou, and all exhibited a logarithmic decrease, which gradually strengthened over time. The development of a double-layered height structure of low-rise and high-rise buildings between 1990 and 2017 was a notable manifestation of the increase in vertical urban height over time. The three factors of city center, altitude, and accessibility, which represent centrality, low relief, proximity to water, and proximity to road networks, highlighted the roles of traffic accessibility and commercial attraction in building height evolution. The importance of location macroscopically depends on the combined effect of the geographical pattern, urban planning, and market forces of cities located on a plain near hill or by a river. The principle of profit orientation restricted spatiotemporal building height patterns.
Understanding the spatiotemporal patterns of three-dimensional urban forms, especially building height, can have important implications for improving urban air quality and mitigating the urban heat island effect by optimizing urban planning and management policies. This study investigated building height evolution and its influencing factors over approximately half a century (1960–2017) in Guangzhou, China. The results indicated that the logarithmic declines in height, quantity, and area of urban buildings followed Zapf's law, which restricts the three-dimensional shape of the urban form. The urban building height decreased from the center to the periphery of the city and decreased with decreasing altitude and increasing distance from main roads. These characteristics constituted the three main spatial differentiation rules of building height in the central district of Guangzhou, and all exhibited a logarithmic decrease, which gradually strengthened over time. The development of a double-layered height structure of low-rise and high-rise buildings between 1990 and 2017 was a notable manifestation of the increase in vertical urban height over time. The three factors of city center, altitude, and accessibility, which represent centrality, low relief, proximity to water, and proximity to road networks, highlighted the roles of traffic accessibility and commercial attraction in building height evolution. The importance of location macroscopically depends on the combined effect of the geographical pattern, urban planning, and market forces of cities located on a plain near hill or by a river. The principle of profit orientation restricted spatiotemporal building height patterns.
2020, 30(6): 1005-1021.
doi: 10.1007/s11769-020-1163-7
Abstract:
Based on urban physical space and theory of landscape ecology, a triune assessment framework —‘size-density- morphology’—was constructed in order to analyze the spatial pattern and the scale effect of urban resilience in Shenyang of China in 2015, and to explore the main impact factors of landscape under different spatial scale backgrounds. The results show that: 1) Urban resilience is an optimal combination of the resilience of size, density, and morphology. The urban resilience of Shenyang displays scale effect; the overall resilience level increases with the increase in scale, while the spatial difference and spatial similarity tend to decrease resilience. 2) As 2 km, 1 km and 2 km are scale inflection points of average value curves for size resilience, density resilience and morphology resilience, respectively in an urban setting; the optimal scale unit of comprehensive resilience is 1 km. Choosing 1 km–2 km as the basic spatial scale better depicts overall pattern and detailed characteristics of resilience in Shenyang. The spatial amplitudes of 0.5 km and 1 km are sensitive points for spatial autocorrelation of morphology and density resilience, size, and comprehensive resilience to scale effect. 3) The major landscape factors of urban size and morphology resilience transform with scale expansion. Aggregation index (AI) has a significant impact on urban resilience at different scales; its influence increases significantly with the increase in scale. 4) The high-level area of comprehensive resilience in Shenyang is the eastern ecological corridor area, while the low value area is the peripheral extension area of the city. To promote the overall level of resilience in Shenyang, this paper argues that the construction of ecological infrastructure should be strengthened in the peripheral extension area in a balanced manner. In the city center, population and building density should be controlled; the intensity of human activities should be reduced; impetus should be placed on landscape heterogeneity; and the homogeneous expansion of the area of construction should be prevented. In the eastern ecological corridors, the exploitation of ecosystem lands should be strictly controlled, and the integrity of the green landscape patches should be maintained.
Based on urban physical space and theory of landscape ecology, a triune assessment framework —‘size-density- morphology’—was constructed in order to analyze the spatial pattern and the scale effect of urban resilience in Shenyang of China in 2015, and to explore the main impact factors of landscape under different spatial scale backgrounds. The results show that: 1) Urban resilience is an optimal combination of the resilience of size, density, and morphology. The urban resilience of Shenyang displays scale effect; the overall resilience level increases with the increase in scale, while the spatial difference and spatial similarity tend to decrease resilience. 2) As 2 km, 1 km and 2 km are scale inflection points of average value curves for size resilience, density resilience and morphology resilience, respectively in an urban setting; the optimal scale unit of comprehensive resilience is 1 km. Choosing 1 km–2 km as the basic spatial scale better depicts overall pattern and detailed characteristics of resilience in Shenyang. The spatial amplitudes of 0.5 km and 1 km are sensitive points for spatial autocorrelation of morphology and density resilience, size, and comprehensive resilience to scale effect. 3) The major landscape factors of urban size and morphology resilience transform with scale expansion. Aggregation index (AI) has a significant impact on urban resilience at different scales; its influence increases significantly with the increase in scale. 4) The high-level area of comprehensive resilience in Shenyang is the eastern ecological corridor area, while the low value area is the peripheral extension area of the city. To promote the overall level of resilience in Shenyang, this paper argues that the construction of ecological infrastructure should be strengthened in the peripheral extension area in a balanced manner. In the city center, population and building density should be controlled; the intensity of human activities should be reduced; impetus should be placed on landscape heterogeneity; and the homogeneous expansion of the area of construction should be prevented. In the eastern ecological corridors, the exploitation of ecosystem lands should be strictly controlled, and the integrity of the green landscape patches should be maintained.
2020, 30(6): 1022-1038.
doi: 10.1007/s11769-020-1164-6
Abstract:
There are many problems, such as poverty, unemployment, poor infrastructure and how to improve the ecological environment, in the shantytowns of old industrial cities. Shantytowns are the most centralized areas with different contradictions, referred to as the ‘problem areas’ of urban sustainable development. The shantytown transformation of old industrial cities is a typical process of unit community disintegration, which is reflected not only in the reconstruction of physical space but also in the community renewal of social spatial integration and culture reconstruction. Based on qualitative research, questionnaires and in-depth interviews, taking Tiexi Worker Village in Shenyang as a research case, this paper attempts to analyse the characteristics and driving forces of the community renewal of shantytown transformation in old industrial cities. We found that the physical space of Tiexi Worker Village has changed considerably, which is embodied in its land use structure, living environment and community service facilities, reflecting the development of community function from simple industrial function to comprehensive functions. The residents in this community have experienced a transformation from a period of homogeneity to one of heterogeneity. The social network of the community has been destroyed. Social stratification, social differentiation and higher fluidity have occurred. Community renewal is mainly affected by macro factors such as policy regulation, economic driving, condition constraints, and micro factors such as residents' choice of living space and willingness to renew their communities. The transformation policy of the old industrial zone and the development policy of the new urban area are the fundamental and deep-seated reasons for the renewal of Tiexi Worker Village, which determine the direction of the renewal and development of the community. The paid use of land and the development of the real estate industry are the direct stimulating factors for the renewal of Tiexi Worker Village, which become the direct reasons for the spatial transformation. The changes in the population in urban and rural areas and the promotion of traffic are the driving factors for the renewal of the community, while the choice of residents and their willingness regarding community renewal are the endogenous forces for promoting community renewal. Finally, the author attempts to put forward a model of the interlaced mechanism of the forming of community renewal at the macroscopic and microcosmic levels, which are the urban renewal and reconstruction and social space differentiation of community residents, respectively.
There are many problems, such as poverty, unemployment, poor infrastructure and how to improve the ecological environment, in the shantytowns of old industrial cities. Shantytowns are the most centralized areas with different contradictions, referred to as the ‘problem areas’ of urban sustainable development. The shantytown transformation of old industrial cities is a typical process of unit community disintegration, which is reflected not only in the reconstruction of physical space but also in the community renewal of social spatial integration and culture reconstruction. Based on qualitative research, questionnaires and in-depth interviews, taking Tiexi Worker Village in Shenyang as a research case, this paper attempts to analyse the characteristics and driving forces of the community renewal of shantytown transformation in old industrial cities. We found that the physical space of Tiexi Worker Village has changed considerably, which is embodied in its land use structure, living environment and community service facilities, reflecting the development of community function from simple industrial function to comprehensive functions. The residents in this community have experienced a transformation from a period of homogeneity to one of heterogeneity. The social network of the community has been destroyed. Social stratification, social differentiation and higher fluidity have occurred. Community renewal is mainly affected by macro factors such as policy regulation, economic driving, condition constraints, and micro factors such as residents' choice of living space and willingness to renew their communities. The transformation policy of the old industrial zone and the development policy of the new urban area are the fundamental and deep-seated reasons for the renewal of Tiexi Worker Village, which determine the direction of the renewal and development of the community. The paid use of land and the development of the real estate industry are the direct stimulating factors for the renewal of Tiexi Worker Village, which become the direct reasons for the spatial transformation. The changes in the population in urban and rural areas and the promotion of traffic are the driving factors for the renewal of the community, while the choice of residents and their willingness regarding community renewal are the endogenous forces for promoting community renewal. Finally, the author attempts to put forward a model of the interlaced mechanism of the forming of community renewal at the macroscopic and microcosmic levels, which are the urban renewal and reconstruction and social space differentiation of community residents, respectively.
2020, 30(6): 1039-1051.
doi: 10.1007/s11769-020-1165-5
Abstract:
China has started shifting from relying on supply management to demand management strategy in addressing its water shortage problems. Water option, a financial derivative for water commodity, has been utilized to manage water demands in the United States and Europe since the 1990s but is still novel to China. In this study we analyzed the pros and cons of China's existing system for water rights transfers and proposed an alternative, flexible trading instrument-water options for China. Incorporating the uncertainty to water option pricing, this study first conducted an empirical analysis of the water option in the water-receiving area of the Hanjiang-Weihe River Transfer Project of China, and then evaluated the benefits of the water option applications. Results show that water option trading can bring water cost saving and increase the potential industrially added value for industrial enterprises in the receiving area, and trading of short-and-medium term water options is more favorable than the long-term water options trading. The novel water option trading proposed in this study, once verified through pilot studies, will be helpful in addressing water shortage problems in China.
China has started shifting from relying on supply management to demand management strategy in addressing its water shortage problems. Water option, a financial derivative for water commodity, has been utilized to manage water demands in the United States and Europe since the 1990s but is still novel to China. In this study we analyzed the pros and cons of China's existing system for water rights transfers and proposed an alternative, flexible trading instrument-water options for China. Incorporating the uncertainty to water option pricing, this study first conducted an empirical analysis of the water option in the water-receiving area of the Hanjiang-Weihe River Transfer Project of China, and then evaluated the benefits of the water option applications. Results show that water option trading can bring water cost saving and increase the potential industrially added value for industrial enterprises in the receiving area, and trading of short-and-medium term water options is more favorable than the long-term water options trading. The novel water option trading proposed in this study, once verified through pilot studies, will be helpful in addressing water shortage problems in China.
2020, 30(6): 1052-1064.
doi: 10.1007/s11769-020-1156-6
Abstract:
Ecological security is the foundation and guarantee of sustainable development, and its importance is increasingly widely recognized and valued by the world. The Yangtze River Basin is an important ecological security barrier in China and the Wanjiang City Belt (WCB) along the Yangtze River is directly related to the ecological security pattern of the entire basin. Based on the Driver-Pressure-State-Impact-Response (DPSIR) model and a geographical information system (GIS) platform, an ecosystem security evaluation index system was constructed to measure and evaluate the evolution of ecosystem security in the WCB, China. Results showed that: 1) From 2000 to 2018, the overall level of ecological security in the study area was in a state of either early warning or medium warning, but the level of ecological security in each prefecture-level city was significantly different. 2) From the perspective of the evolution of the ecosystem, the value of its comprehensive evaluation index dropped from 4.255 in 2000 to 3.885 in 2018. From the perspective of subsystems, the value of Pressure comprehensive evaluation index is much higher than that of other subsystems, indicating that during the rapid development of the social economy, the pressure on the natural environment tended to rise, and triggered changes in the State and Response subsystems. 3) The coefficient of variation (CV) of the Driver was much higher than other factors influencing the ecological security system. There are large differences in the economic development and ecological evolution of the cities in the WCB. This study has improved the theoretical research on regional ecological security, and has certain practical guiding significance for building a beautiful, green and sustainable China and promoting global ecological security.
Ecological security is the foundation and guarantee of sustainable development, and its importance is increasingly widely recognized and valued by the world. The Yangtze River Basin is an important ecological security barrier in China and the Wanjiang City Belt (WCB) along the Yangtze River is directly related to the ecological security pattern of the entire basin. Based on the Driver-Pressure-State-Impact-Response (DPSIR) model and a geographical information system (GIS) platform, an ecosystem security evaluation index system was constructed to measure and evaluate the evolution of ecosystem security in the WCB, China. Results showed that: 1) From 2000 to 2018, the overall level of ecological security in the study area was in a state of either early warning or medium warning, but the level of ecological security in each prefecture-level city was significantly different. 2) From the perspective of the evolution of the ecosystem, the value of its comprehensive evaluation index dropped from 4.255 in 2000 to 3.885 in 2018. From the perspective of subsystems, the value of Pressure comprehensive evaluation index is much higher than that of other subsystems, indicating that during the rapid development of the social economy, the pressure on the natural environment tended to rise, and triggered changes in the State and Response subsystems. 3) The coefficient of variation (CV) of the Driver was much higher than other factors influencing the ecological security system. There are large differences in the economic development and ecological evolution of the cities in the WCB. This study has improved the theoretical research on regional ecological security, and has certain practical guiding significance for building a beautiful, green and sustainable China and promoting global ecological security.
2020, 30(6): 1065-1080.
doi: 10.1007/s11769-020-1166-4
Abstract:
Heat flux is important for studying interactions between atmosphere and lake. The heat exchange between air-water interfaces is one of the important ways to govern the temperature of the water surface. Heat exchange between the air-water interfaces and the surrounding environment is completed by solar radiation, conduction, and evaporation, and all these processes mainly occur at the air-water interface. Hulun Lake was the biggest lake which is also an important link and an indispensable part of the water cycle in Northeast China. This study mapped surface energy budget to better understand spatial and temporal variations in Hulun Lake in China from 2001 to 2018. Descriptive statistics were computed to build a historical time series of mean monthly heat flux at daytime and nighttime from June to September during 2001–2018. Remote sensing estimation methods we used was suitable for Hulun Lake (R2 = 0.81). At month scale, shortwave radiation and latent heat flux were decrease from June to September. However, the maximum sensible heat flux appeared in September. Net longwave radiation was the largest in August. The effective heat budget showed that Hulun Lake gained heat in the frost-free season with highest value in June (686.31 W/m2), and then steadily decreased to September (439.76 W/m2). At annual scale, net longwave radiation, sensible heat flux and latent heat flux all show significant growth trend from 2001 to 2018 (P < 0.01). Wind speed had the well correlation on sensible heat flux and latent heat flux. Water surface temperature showed the highest coefficient in sensitivity analysis.
Heat flux is important for studying interactions between atmosphere and lake. The heat exchange between air-water interfaces is one of the important ways to govern the temperature of the water surface. Heat exchange between the air-water interfaces and the surrounding environment is completed by solar radiation, conduction, and evaporation, and all these processes mainly occur at the air-water interface. Hulun Lake was the biggest lake which is also an important link and an indispensable part of the water cycle in Northeast China. This study mapped surface energy budget to better understand spatial and temporal variations in Hulun Lake in China from 2001 to 2018. Descriptive statistics were computed to build a historical time series of mean monthly heat flux at daytime and nighttime from June to September during 2001–2018. Remote sensing estimation methods we used was suitable for Hulun Lake (R2 = 0.81). At month scale, shortwave radiation and latent heat flux were decrease from June to September. However, the maximum sensible heat flux appeared in September. Net longwave radiation was the largest in August. The effective heat budget showed that Hulun Lake gained heat in the frost-free season with highest value in June (686.31 W/m2), and then steadily decreased to September (439.76 W/m2). At annual scale, net longwave radiation, sensible heat flux and latent heat flux all show significant growth trend from 2001 to 2018 (P < 0.01). Wind speed had the well correlation on sensible heat flux and latent heat flux. Water surface temperature showed the highest coefficient in sensitivity analysis.
2020, 30(6): 1081-1094.
doi: 10.1007/s11769-020-1167-3
Abstract:
The Mongolian Plateau is one of the regions most sensitive to climate change, the more obvious increase of temperature in 21st century here has been considered as one of the important causes of drought and desertification. It is very important to understand the multi-year variation and occurrence characteristics of drought in the Mongolian Plateau to explore the ecological environment and the response mechanism of surface materials to climate change. This study examines the spatio-temporal variations in drought and its frequency of occurrence in the Mongolian Plateau based on the Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) (1982–1999) and the Moderate-resolution Imaging Spectroradiometer (MODIS) (2000–2018) datasets; the Temperature Vegetation Dryness Index (TVDI) was used as a drought evaluation index. The results indicate that drought was widespread across the Mongolian Plateau between1982 and 2018, and aridification incremented in the 21st century. Between 1982 and 2018, an area of 164.38×104 km2/yr suffered from drought, accounting for approximately 55.28% of the total study area. An area of approximately 150.06×104 km2 (51.43%) was subject to more than 160 droughts during 259 months of the growing seasons between 1982 and 2018. We observed variable frequencies of drought occurrence depending on land cover/land use types. Drought predominantly occurred in bare land and grassland, both of which accounting for approximately 79.47% of the total study area. These terrains were characterized by low vegetation and scarce precipitation, which led to frequent and extreme drought events. We also noted significant differences between the areal distribution of drought, drought frequency, and degree of drought depending on the seasons. In spring, droughts were widespread, occurred with a high frequency, and were severe; in autumn, they were localized, frequent, and severe; whereas, in summer, droughts were the most widespread and frequent, but less severe. The increase in temperature, decrease in precipitation, continuous depletion of snow cover, and intensification of human activities have resulted in a water deficit. More severe droughts and aridification have affected the distribution and functioning of terrestrial ecosystems, causing changes in the composition and distribution of plants, animals, microorganisms, conversion between carbon sinks and carbon sources, and biodiversity. We conclude that regional drought events have to be accurately monitored, whereas their occurrence mechanisms need further exploration, taking into account nature, climate, society and other influencing factors.
The Mongolian Plateau is one of the regions most sensitive to climate change, the more obvious increase of temperature in 21st century here has been considered as one of the important causes of drought and desertification. It is very important to understand the multi-year variation and occurrence characteristics of drought in the Mongolian Plateau to explore the ecological environment and the response mechanism of surface materials to climate change. This study examines the spatio-temporal variations in drought and its frequency of occurrence in the Mongolian Plateau based on the Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) (1982–1999) and the Moderate-resolution Imaging Spectroradiometer (MODIS) (2000–2018) datasets; the Temperature Vegetation Dryness Index (TVDI) was used as a drought evaluation index. The results indicate that drought was widespread across the Mongolian Plateau between1982 and 2018, and aridification incremented in the 21st century. Between 1982 and 2018, an area of 164.38×104 km2/yr suffered from drought, accounting for approximately 55.28% of the total study area. An area of approximately 150.06×104 km2 (51.43%) was subject to more than 160 droughts during 259 months of the growing seasons between 1982 and 2018. We observed variable frequencies of drought occurrence depending on land cover/land use types. Drought predominantly occurred in bare land and grassland, both of which accounting for approximately 79.47% of the total study area. These terrains were characterized by low vegetation and scarce precipitation, which led to frequent and extreme drought events. We also noted significant differences between the areal distribution of drought, drought frequency, and degree of drought depending on the seasons. In spring, droughts were widespread, occurred with a high frequency, and were severe; in autumn, they were localized, frequent, and severe; whereas, in summer, droughts were the most widespread and frequent, but less severe. The increase in temperature, decrease in precipitation, continuous depletion of snow cover, and intensification of human activities have resulted in a water deficit. More severe droughts and aridification have affected the distribution and functioning of terrestrial ecosystems, causing changes in the composition and distribution of plants, animals, microorganisms, conversion between carbon sinks and carbon sources, and biodiversity. We conclude that regional drought events have to be accurately monitored, whereas their occurrence mechanisms need further exploration, taking into account nature, climate, society and other influencing factors.
2020, 30(6): 1095-1110.
doi: 10.1007/s11769-020-1160-x
Abstract:
Accurate estimations of evapotranspiration (ET) are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges. Based on input data processing, this paper simulates the temporal and spatial variation of ET in the Dajiuhu Basin from 1990 to 2018 using the BEPS-TerrainLab V2.0 model. Compared with the ET measured by an eddy covariance (EC) tower, the model explained 80.1% of the ET variation. From 1990 to 2018, the average annual ET in the Dajiuhu Basin was 1262.7 mm/yr indicating a downward trend (–27.12 mm/yr). In 2005, a sudden change point was observed based on the Mann-Kendall (MK) test and 3-year moving t-test. Around 2005, the downward trend in ET slowed and the proportional trend of ET to precipitation changed from upward trend to downward trend. Regarding spatial distribution, the ET in the basin's central part was smaller than that in the basin's surrounding area, the ET of the southern slope was higher than that of the northern slope, and the decrease in the ET rate on the sunny side was lower than that on the shady side. ET decreased as the elevation increased, with the fastest decrease observed between 2184 and 2384 m. For different landcover types, the average ET exhibited the following order: deciduous forest > mixed forest > wetland > grass > agriculture land. Decreased solar radiation is the main reason for the decreased ET in the Dajiuhu Basin, followed by increased wind speed and relative humidity, which together contribute 83.9% to the ET trend. This paper provides a theoretical basis for the study of ET changes and the mechanism of ET and provides a decision-making reference for water resource management in the Dajiuhu Basin and even the South-to-North Water Transfer Project.
Accurate estimations of evapotranspiration (ET) are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges. Based on input data processing, this paper simulates the temporal and spatial variation of ET in the Dajiuhu Basin from 1990 to 2018 using the BEPS-TerrainLab V2.0 model. Compared with the ET measured by an eddy covariance (EC) tower, the model explained 80.1% of the ET variation. From 1990 to 2018, the average annual ET in the Dajiuhu Basin was 1262.7 mm/yr indicating a downward trend (–27.12 mm/yr). In 2005, a sudden change point was observed based on the Mann-Kendall (MK) test and 3-year moving t-test. Around 2005, the downward trend in ET slowed and the proportional trend of ET to precipitation changed from upward trend to downward trend. Regarding spatial distribution, the ET in the basin's central part was smaller than that in the basin's surrounding area, the ET of the southern slope was higher than that of the northern slope, and the decrease in the ET rate on the sunny side was lower than that on the shady side. ET decreased as the elevation increased, with the fastest decrease observed between 2184 and 2384 m. For different landcover types, the average ET exhibited the following order: deciduous forest > mixed forest > wetland > grass > agriculture land. Decreased solar radiation is the main reason for the decreased ET in the Dajiuhu Basin, followed by increased wind speed and relative humidity, which together contribute 83.9% to the ET trend. This paper provides a theoretical basis for the study of ET changes and the mechanism of ET and provides a decision-making reference for water resource management in the Dajiuhu Basin and even the South-to-North Water Transfer Project.
2020, 30(6): 1111-1128.
doi: 10.1007/s11769-020-1146-8
Abstract:
Since the 1980s, Japan has witnessed an unprecedented decline in agriculture chiefly due to farmers' aging, depopulation, and unfavorable socio-economic conditions. This development has resulted in an increase of farmland abandonment (FLA) across the country. However, it remains unclear as to how and to what extent FLA is influenced by intraregional agricultural characteristics. As such, this article discusses the issue of FLA by taking a closer look at the Chugoku and Shikoku region, as it has experienced the highest FLA rates in Japan in recent years. For this analysis, a total of 25 indicators retrieved from the census of agriculture and forestry at the former municipalities scale were selected to describe intraregional agricultural characteristics. We employed principal component analysis (PCA) to evaluate agricultural characteristics, while multiple linear regressions (MLR) was applied to explore their correlations with FLA and spatial variations. First, there are strong intraregional differences in the agricultural characteristics across the Chugoku and Shikoku region, with eight different principle components (PCs) describing their characteristics. Second, variables measuring agricultural characteristics explain nearly 52.8% of the variation in FLA in our sample. The sales orientation and scale of agriculture have the strongest negative correlation to FLA in the region, while the status of agricultural succession displays the strongest positive correlation to FLA. Third, in areas where agriculture is more stable and easier to maintain, FLA is more strongly influenced by changes in agricultural characteristics than by geographical variations. We argue that localized approaches and policies for future management need to take intraregional differences in agricultural characteristics and FLA into account. Our findings help to explain spatial variations in agricultural characteristics and FLA in regional contexts, suggesting the need for better-informed farmland use policies to mitigate further abandonment.
Since the 1980s, Japan has witnessed an unprecedented decline in agriculture chiefly due to farmers' aging, depopulation, and unfavorable socio-economic conditions. This development has resulted in an increase of farmland abandonment (FLA) across the country. However, it remains unclear as to how and to what extent FLA is influenced by intraregional agricultural characteristics. As such, this article discusses the issue of FLA by taking a closer look at the Chugoku and Shikoku region, as it has experienced the highest FLA rates in Japan in recent years. For this analysis, a total of 25 indicators retrieved from the census of agriculture and forestry at the former municipalities scale were selected to describe intraregional agricultural characteristics. We employed principal component analysis (PCA) to evaluate agricultural characteristics, while multiple linear regressions (MLR) was applied to explore their correlations with FLA and spatial variations. First, there are strong intraregional differences in the agricultural characteristics across the Chugoku and Shikoku region, with eight different principle components (PCs) describing their characteristics. Second, variables measuring agricultural characteristics explain nearly 52.8% of the variation in FLA in our sample. The sales orientation and scale of agriculture have the strongest negative correlation to FLA in the region, while the status of agricultural succession displays the strongest positive correlation to FLA. Third, in areas where agriculture is more stable and easier to maintain, FLA is more strongly influenced by changes in agricultural characteristics than by geographical variations. We argue that localized approaches and policies for future management need to take intraregional differences in agricultural characteristics and FLA into account. Our findings help to explain spatial variations in agricultural characteristics and FLA in regional contexts, suggesting the need for better-informed farmland use policies to mitigate further abandonment.
2020, 30(6): 1129-1142.
doi: 10.1007/s11769-020-1168-2
Abstract:
Land desertification and aeolian activity are currently the greatest threats to alpine ecological environments and are also the primary challenges of desertification control and ecological restoration projects. Afforestation of sandy lands around the Qinghai Lake in China has effectively controlled the desertification of this watershed. However, certain issues remain which challenge its overall success, including lack of diverse biological species and poor theoretical understanding of aeolian processes, such as controlling wind-sand flow in relation to complex alpine ecological factors. Therefore, to help improving afforestation techniques, this research focused on Hippophae rhamnoides, Salix cheilophila, Pinus sylvestris, Populus simonii and Artemisia desertorum vegetation implanted in the mobile dunes on the eastern shore of Qinghai Lake. Aeolian transport characteristics and annual changes to community ecological factors from 2010–2016 were monitored in comparison with uncontrolled sand dunes. Based on simultaneous observations using gradient anemometers and sand samplers, it was found that the aeolian activities exhibited the following features: 1) In re-vegetated lands, the logarithmic growth of wind speed was disrupted by the wind speed amplification in the middle and high layers and wind speed reduction in the low layers, while vegetation had significant wind-breaking (> 37%) and sand-fixing (> 85%) effects in 2016.2) Wind speeds in re-vegetated lands and mobile dunes showed a linear correlation, especially in lower layers of H. rhamnoides and S. cheilophila, while sand transport in re-vegetated land increased linearly or exponentially with increasing wind speed. 3) The four artificial shrubs and forests had greater sand deposition with intensities of 280–860 t/(ha·yr), largely concentrated during winter and spring which accounted for 60%–85% of the annual cycle, while A. desertorum experienced significant root undercutting; and 4) Intensity of aeolian activity in re-vegetated lands, except for A. desertorum, was significantly negative with respect to plant growth structure, community cover, topsoil moisture, and regional precipitation. Overall, these five sand-binding species produced optimistic wind-sand protection effects for the alpine sandy lands, which relied on the plants' physical disturbance of wind-sand flow during the early stages of community development. In comparison, H. rhamnoides and S. cheilophila individually maintained stable wind-sand protection effects, while P. sylvestris and P. simonii were better in mixing with other shrubs and herbs to achieve a comprehensive ecological system for future control of aeolian activity.
Land desertification and aeolian activity are currently the greatest threats to alpine ecological environments and are also the primary challenges of desertification control and ecological restoration projects. Afforestation of sandy lands around the Qinghai Lake in China has effectively controlled the desertification of this watershed. However, certain issues remain which challenge its overall success, including lack of diverse biological species and poor theoretical understanding of aeolian processes, such as controlling wind-sand flow in relation to complex alpine ecological factors. Therefore, to help improving afforestation techniques, this research focused on Hippophae rhamnoides, Salix cheilophila, Pinus sylvestris, Populus simonii and Artemisia desertorum vegetation implanted in the mobile dunes on the eastern shore of Qinghai Lake. Aeolian transport characteristics and annual changes to community ecological factors from 2010–2016 were monitored in comparison with uncontrolled sand dunes. Based on simultaneous observations using gradient anemometers and sand samplers, it was found that the aeolian activities exhibited the following features: 1) In re-vegetated lands, the logarithmic growth of wind speed was disrupted by the wind speed amplification in the middle and high layers and wind speed reduction in the low layers, while vegetation had significant wind-breaking (> 37%) and sand-fixing (> 85%) effects in 2016.2) Wind speeds in re-vegetated lands and mobile dunes showed a linear correlation, especially in lower layers of H. rhamnoides and S. cheilophila, while sand transport in re-vegetated land increased linearly or exponentially with increasing wind speed. 3) The four artificial shrubs and forests had greater sand deposition with intensities of 280–860 t/(ha·yr), largely concentrated during winter and spring which accounted for 60%–85% of the annual cycle, while A. desertorum experienced significant root undercutting; and 4) Intensity of aeolian activity in re-vegetated lands, except for A. desertorum, was significantly negative with respect to plant growth structure, community cover, topsoil moisture, and regional precipitation. Overall, these five sand-binding species produced optimistic wind-sand protection effects for the alpine sandy lands, which relied on the plants' physical disturbance of wind-sand flow during the early stages of community development. In comparison, H. rhamnoides and S. cheilophila individually maintained stable wind-sand protection effects, while P. sylvestris and P. simonii were better in mixing with other shrubs and herbs to achieve a comprehensive ecological system for future control of aeolian activity.
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