Subaqueous distributary channel sandbodies within delta fronts are crucial reservoirs in continental petroliferous basins.Understanding the spatiotemporal transition of river patterns in these channels is essential fo...Subaqueous distributary channel sandbodies within delta fronts are crucial reservoirs in continental petroliferous basins.Understanding the spatiotemporal transition of river patterns in these channels is essential for accurate evaluation and prediction of oil and gas reservoirs,as well as for providing direct evidence of basin evolution.In the Yabus Formation of the Sag A of Melut Basin,a comprehensive analysis involving sequence division,sedimentary characteristics,seismic facies,highresolution reservoir inversion,and sand body distribution revealed significant insights.During the Yabus Formation deposition,three intermediate base-level cycles were identified,each showing transition phenomena in the river patterns of subaqueous distributary channels within the delta front.Clear identification criteria for different river patterns were established.Braided subaqueous distributary channels exhibited dominant vertical accretion,high sand content,significant sandstone thickness,and continuousstrong amplitude seismic reflections.While the braidedmeandering transition pattern showed a combination of vertical and lateral accretion,medium sand content,moderate sandstone thickness,and medium continuousmedium strong amplitude seismic reflections.Meandering subaqueous distributary channels were characterized by lateral accretion,low sand content,minimal sandstone thickness,weak continuous-weak amplitude seismic reflections,and mud-rich inversion features.The primary control factor influencing the transition of river patterns in these channels was identified as the long-term base-level cycle,shaped by paleotopography and sediment supply.Braided subaqueous distributary channels emerged as the main exploration interval for structural prospects,serving as lateral high-speed migration pathways.Dendritic braided and meandering transition intervals were deemed favorable for both structure-lithologic prospects and the expansion of new exploration fields and layers.展开更多
Investigation of groundwater pollution has been carried out on multiple typical karst underground river systems in recent years in order to reveal the characteristics and mechanism of underground river pollution. Thro...Investigation of groundwater pollution has been carried out on multiple typical karst underground river systems in recent years in order to reveal the characteristics and mechanism of underground river pollution. Through the summary of the survey results, five characteristics of underground river pollution have been revealed, including directionality, weak hysteresis, easier for reversibility, linear and intermittent(or seasonal); combining with karst geomorphic types, pollution sources(primordial, secondary pollution and compound), pollution ways and pollution receptors, three basic pollution patterns of the underground river were depicted: Recharge area pollution, runoff area pollution and discharge area pollution. At the same time, the study discloses the reality of the underground river pollution is the three basic patterns and their subgenera in combination with super imposition on the space and time. And from the angle of the hydrogeological model, the study expounds the process of underground river pollution. Finally, the study gives naming rules of pollution pattern of the underground river and sets up PISAB method of pattern recognition. The results provide scientific basis for pollution repair and management of underground river in the southwest karst region.展开更多
The three-river source region (TRSR, including Yangtze, Yellow and Lancang rivers), located in the Qinghai-Tibetan Plateau, China, is a typical alpine zone with apparent ecosystem vulnerability and sensitivity. In thi...The three-river source region (TRSR, including Yangtze, Yellow and Lancang rivers), located in the Qinghai-Tibetan Plateau, China, is a typical alpine zone with apparent ecosystem vulnerability and sensitivity. In this paper, we introduced many interdisciplinary factors, such as landscape pattern indices (Shannon diversity index and Shannon evenness index) and extreme climate factors (number of extreme high temperature days, number of extreme low temperature days, and number of extreme precipitation days), to establish a new model for evaluating the spatial patterns of ecosystem vulnerability changes in the TRSR. The change intensity (CI) of ecosystem vulnerability was also analyzed. The results showed that the established evaluation model was effective and the ecosystem vulnerability in the whole study area was intensive. During the study period of 2001–2011, there was a slight degradation in the eco-environmental quality. The Yellow River source region had the best eco-environmental quality, while the Yangtze River source region had the worst one. In addition, the zones dominated by deserts were the most severely deteriorated areas and the eco-environmental quality of the zones occupied by evergreen coniferous forests showed a better change. Furthermore, the larger the change rates of the climate factors (accumulative temperature of ≥10°C and annual average precipitation) are, the more intensive the CI of ecosystem vulnerability is. This study would provide a scientific basis for the eco-environmental protection and restoration in the TRSR.展开更多
The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuit...The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR＇s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR＇s courses into two periods, and proposes its changing pattern; concludes the character- istic of diversion points of courses shift events; calculates the velocity of courses shifts, gra- dient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types： the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipita- tion and human activities.展开更多
The question of how to generate maximum socio-economic benefits while at the same time minimizing input from urban land resources lies at the core of regional ecological civilization construction. We apply stochastic ...The question of how to generate maximum socio-economic benefits while at the same time minimizing input from urban land resources lies at the core of regional ecological civilization construction. We apply stochastic frontier analysis （SFA） in this study to municipal input-output data for the period between 2005 and 2014 to evaluate the urbanization efficiency of 110 cities within the Yangtze River Economic Belt （YREB） and then further assess the spatial association characteristics of these values. The results of this study initially reveal that the urbanization efficiency of the YREB increased from 0.34 to 0.53 between 2005 and 2014, a significant growth at a cumulative rate of 54.07%. Data show that the efficiency growth rate of cities within the upper reaches of the Yangtze River has been faster than that of their counterparts in the middle and lower reaches, and that there is also a great deal of ad- ditional potential for growth in urbanization efficiency across the whole area. Secondly, results show that urbanization efficiency conforms to a ＂bar-like＂ distribution across the whole area, gradually decreasing from the east to the west. This trend highlights great intra-provincial differences, but also striking inter-provincial variation within the upper, middle, and lower reaches of the Yangtze River. The total urbanization efficiency of cities within the lower reaches of the river has been the highest, followed successively by those within the middle and upper reaches. Finally, values for Moran＇s / within this area remained higher than zero over the study period and have increased annually; this result indicates a positive spatial correlation between the urbanization efficiency of cities and annual increments in agglomeration level. Our use of the local indicators of spatial association （LISA） statistic has enabled us to quantify characteristics of ＂small agglomeration and large dispersion＂. Thus, ＂high- high＂ （H-H） agglomeration areas can be seen to have spread outwards from around Zhejiang Province and the city of Shanghai, while areas characterized by ＂low-low＂ （L-L） patterns are mainly concentrated in the north of Anhui Province and in Sichuan Province. The framework and results of this research are of considerable significance to our understanding of both land use sustainability and balanced development.展开更多
The influence of anthropogenic activities,especially artificial dykes,on the coastal wetland landscape is now considered as a serious problem to the coastal ecosystem.It is important and necessary to analyze changes o...The influence of anthropogenic activities,especially artificial dykes,on the coastal wetland landscape is now considered as a serious problem to the coastal ecosystem.It is important and necessary to analyze changes of coastal landscape pattern under the influence of artificial dykes for the protection and management of coastal wetland.Our study aimed to reveal the quantitative characteristics of the coastal wetland landscape and its spatial-temporal dynamics under the influence of artificial dykes in the Yellow River delta(YRD).It was analyzed by the methods of the statistical analysis of landscape structure,five selected landscape indices and the changes of spatial centroids of three typical wetland types,including reed marshes,tidal fiats and aquaculture-salt fields.The results showed that:(1)Reduction of wetland area,especially the degradation of natural wetlands,had been the principal problem since the dykes were constructed in the YRD.The dykes created conditions for the development of artificial wetlands.However,the new born artificial wetlands were still less than the vanished natural wetlands.(2)Compared with the open area,the building of artificial dykes significantly speeded up the changes of landscape patterns and the aggravation of the landscape fragmentation in the closed area.(3)The changes of area-weighted centroids of three typical wetland landscapes were greatly affected by dykes,and the movement of the centroid of the aquaculture-salt field was very sensitive to the dykes constructed in the corresponding period.展开更多
Agricultural landscape along the riparian zones is designated as important landscape components for partly controlling water quality, biodiversity, as well as for their aesthetic role in landscapes. Therefore, the cha...Agricultural landscape along the riparian zones is designated as important landscape components for partly controlling water quality, biodiversity, as well as for their aesthetic role in landscapes. Therefore, the change of agricultural landscape along the riparian zones is at the top of the agenda for many policy makers and landscape planners. As a basis for conservation management, sufficient information about landscape structure should be provided. In the present study, we reconstructed the former landscape structure and elucidated the changes in landscape patterns during a period of about 15 years. Two sets of maps were used： a landsat-5 TM image （1987） and landsat-7 ETM image （2002）. The frequency index, landscape diversity index and landscape fragmentation index were calculated for analyses. The results showed that： （1） the areas of the irrigated land, river, forest and beach landscape classes presented a decreasing trend while the areas of landscape classes of pool, paddy fields, dry land and construction land increased. （2） Disturbed by human activity, landscape diversity index increased but landscape fragmentation index decreased. In short, Human activities have had important influences on agricultural landscape of the riparian zones along the Yellow River in Henan Province.展开更多
The Yellow River Delta wetland is the youngest wetland ecosystem in China's warm temperate zone. To better understand how its landscape pattern has changed over time and the underlying factors responsible, this st...The Yellow River Delta wetland is the youngest wetland ecosystem in China's warm temperate zone. To better understand how its landscape pattern has changed over time and the underlying factors responsible, this study analyzed the dynamic changes of wetlands using five Landsat series of images, namely MSS(Mulri Spectral Scanner), TM(Thematic Mapper), and OLI(Operational Land Imager) sensors in 1976, 1986, 1996, 2006, and 2016. Object-oriented classification and the combination of spatial and spectral features and both the Normalized Difference Vegetation Index(NDVI) and Normalized Difference Water Index(NDWI), as well as brightness characteristic indices, were used to classify the images in eCognition software. Landscape pattern changes in the Yellow River Delta over the past 40 years were then delineated using transition matrix and landscape index methods. Results show that: 1) from1976 to 2016, the total area of wetlands in the study area decreased from 2594.76 to 2491.79 km^2, while that of natural wetlands decreased by 954.03 km^2 whereas human-made wetlands increased by 851.06 km^2. 2) The transformation of natural wetlands was extensive: 31.34% of those covered by Suaeda heteropteras were transformed into reservoirs and ponds, and 24.71% with Phragmites australis coverage were transformed into dry farmland. Some human-made wetlands were transformed into non-wetlands types: 1.55% of reservoirs and ponds became construction land, and likewise 21.27% were transformed into dry farmland. 3) From 1976 to 2016, as the intensity of human activities increased, the number of landscape types in the study area continuously increased. Patches were scattered and more fragmented. The whole landscape became more complex. In short, over the past 40 years, the wetlands of the Yellow River Delta have been degraded, with the area of natural wetlands substantially reduced. Human activities were the dominant forces driving these changes in the Yellow River Delta.展开更多
Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversit...Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversity. The river-lake relationship between Mekong River and Tonle Sap Lake is unique and has always been a major focus in the international community. The land terrain and under-water topography were used to analyze the morphological characteristics of Cambodia Mekong Delta and Tonle Sap Lake. Long series of hydrological data of river-lake controlling stations were used to analyze the water level variation characteristics and water volume exchange pattern between Mekong River and Tonle Sap Lake, and the response relationship to river-lake morphological characteristics were also researched. The results show that: Cambodia Mekong Delta and Tonle Sap Lake Area is low-lying and flat with gentle channel gradient and water surface gradient, making the relationship between water level and area (or volume) smooth. The channel storage capacity of Mekong River and Tonle Sap River is not enough compared to the inflow, so vast flooding plain is extremely prone to be inundated, making the flood relationships between the left and right banks become very complicated. Tonle Sap Lake is a seasonal freshwater lake with water flowing in and flowing out, and the timing and intensity of water exchange with Mekong River are closely related to the water flow resistance at the exit section of Tonle Sap Lake and the cross-sectional area of Tonle Sap River, which can be reflected by the river-lake water level difference and the water level of Tonle Sap River. Affected by the river-lake morphological characteristics, the water exchange intensity between Mekong River and Tonle Sap Lake is great. Tonle Sap Lake not only stores 14.4% of flood volume (39.7 billion m3) from the Mekong River every year, but also supplies 29.7% of dry water (69.4 billion m3) to the Mekong River. Influenced by the adjustment of the floodplain, the water level fluctuation of Mekong River and Tonle Sap Lake is slow, and the rising and droop rates of water level are positively correlated with the floodplain storage area. The research results will help to understand the relationship mechanism between Mekong River and Tonle Sap Lake and provide a scientific basis for the comprehensive governance of Cambodia Mekong Delta and Tonle Sap Lake Area.展开更多
This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite netwo...This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite network projection from an IFFS firm-city data source, we mapped three IFFS networks in the YRD in 2005, 2010, and 2015. A range of statistical indicators were used to explore changes in the spatial patterns of the three networks. The underlying influence of marketization, globalization, decentralization, and integration was then explored. It was found that the connections between Shanghai and other nodal cities formed the backbones of these networks. The effects of a city's administrative level and provincial administrative borders were generally obvious. We found several specific spatial patterns associated with IFFS. For example, the four non-administrative centers of Ningbo, Suzhou, Lianyungang, and Nantong were the most connected cities and played the role of gateway cities. Furthermore, remarkable regional equalities were found regarding a city's IFFS network provision, with notable examples in the weakly connected areas of northern Jiangsu and southwestern Zhejiang. Finally, an analysis of the driving mechanisms demonstrated that IFFS network changes were highly sensitive to the influences of marketization and globalization, while regional integration played a lesser role in driving changes in IFFS networks.展开更多
The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. Th...The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as： anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess ahd interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anas- tomosing reaches have a relatively high bed slope （0.86‰） and coarser sediment bed material （d50 = 3.5 mm）. In contrast, meandering reaches have a low slope （0.30‰） and fine sediment bed material （d50 = 0.036 mm）. The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength （i.e. cohesive versus non-cohesive versus channel boundaries）. Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers （Baihe and Heihe rivers respectively）. Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.展开更多
Based on the information from forest resources distribution maps of Luoning County of 1983 and 1999, six indices were used to analyze spatial patterns and dynamics of forest landscapes of t...Based on the information from forest resources distribution maps of Luoning County of 1983 and 1999, six indices were used to analyze spatial patterns and dynamics of forest landscapes of the typical region in the middle of the Yihe-Luohe river basin. These indices include patch number, mean patch area, fragment index, patch extension index, etc. The results showed that: (1) There was a rapid increase in the number of patch and total area from 1983 to 1999 in the study area. The fragment degree became very high. (2) The area of all the forest patch types had witnessed great changes. The fractal degree of each forest patch type became big from 1983 to 1999. The mean extension index of Robinia pseudoacacia forest, non-forest, shrub forest, sparse forest, and Quercus species forest increased rapidly, but that of economic forest became zero. The fractal dimension each showed that forest coverage has been promoted. (3) The changes of landscape patterns were different in different geomorphic regions. From 1983 to 1999 the vegetation cover area, the gross number and the density of patch, diversity and evenness of landscape were all reduced greatly in gullies and ravines, but the maximum area and the mean area of patch types were increased. In hilly region, both the forest cover area and the number of patch increased from 1983 to 1999, but the mean area of patch was reduced greatly. In mountain region, even though the area under forest canopy reduced from 1983 to 1999, the patch number was increased greatly, the mean area of all patch types was reduced, the extension index, diversity index and evenness index of landscape were all increased. Furthermore, because of different types of land use, human activity and terrain, the vegetation changes on northern and southern mountain slopes were different. According to these analyses, the main driving forces, such as the policies of management, market economy, influence of human activities etc. are brought out.展开更多
Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria w...Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria were determined. Four flow patterns were identified: mixed, locally unstable, continuously stratified, and two-layer flow. Temperature distributions of the four types of flow patterns were analyzed and compared.The critical Froude numbers for unstable flow, FDcr1, and stable flow, FDcr2, were determined to be 6 and 1, respectively, and comparison of FDcr1 and FDcr2 to the peak Froude numbers, FD1 at the outer bank and FD2 at the inner bank along the anabranch, allowed the flow patterns to be assessed. Then, a discriminant based on initial Jeffreys-Keulegan stability parameters was established to distinguish the flow stages from twolayer flow to completely mixed flow. It is indicated that the three critical Jeffreys-Keulegan parameters increased with the diversion angle of braided rivers. Results also show that, compared to the stratified flow in straight and curved channels, it was more difficult for braided stratified flow to maintain as two-layer flow, and it more easily became mixed flow. Consequently, empirical expressions for stability criteria of the thermally stratified shear flow in braided rivers are presented.展开更多
Study on the relationship between landscape beauty and ecological beauty is an important scientifi c problem that refl ects the nature of man-land relation, and current academic researches on this topic are most based...Study on the relationship between landscape beauty and ecological beauty is an important scientifi c problem that refl ects the nature of man-land relation, and current academic researches on this topic are most based on a single perspective. Therefore, this paper took the Confucius Temple–Qinhuai River Scenic Area in Nanjing City as a typical case of urban traditional cultural tourism destination, adopted landscape pattern indexes and balanced incomplete block comparison and evaluation method as the evaluation standards of ecological beauty and landscape beauty, and analyzed the coupling characteristics and rules of landscape pattern and landscape aesthetics. The results showed that(a) The overall landscape of the study area had higher fragmentation degree, but different landscape groups were infl uenced by different human interventions, landscape patches showed moderate diversity and heterogeneity, patch area, spatial distribution and spatial aggregation degree showed structural differences.(b) The locals and visitors had aesthetic perception of the study area, but preferred the beautiful natural scenery of the Qinhuai River, as well as the historical buildings and cultural landscapes that contain rich memories of the city.(c) Landscape pattern and landscape aesthetics showed coupled complementation and harmonious coexistence. The Confucius Temple–Qinhuai River Scenic Area has profound historical and cultural background, but it has witnessed gradual loss of cultural characteristics and fast "delocalization" against the background of rapid urbanization. As an urban traditional cultural tourism destination, it carries the responsibility of protecting city memories and inheriting regional cultures.展开更多
The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source reg...The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections （I, II and III） based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined （some reaches partly-confined） valleys while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections （sections I-V） based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined （some short reaches partly-confined） valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief （elevation, gradient, aspect, valley alignment and confinement） of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.展开更多
文摘Subaqueous distributary channel sandbodies within delta fronts are crucial reservoirs in continental petroliferous basins.Understanding the spatiotemporal transition of river patterns in these channels is essential for accurate evaluation and prediction of oil and gas reservoirs,as well as for providing direct evidence of basin evolution.In the Yabus Formation of the Sag A of Melut Basin,a comprehensive analysis involving sequence division,sedimentary characteristics,seismic facies,highresolution reservoir inversion,and sand body distribution revealed significant insights.During the Yabus Formation deposition,three intermediate base-level cycles were identified,each showing transition phenomena in the river patterns of subaqueous distributary channels within the delta front.Clear identification criteria for different river patterns were established.Braided subaqueous distributary channels exhibited dominant vertical accretion,high sand content,significant sandstone thickness,and continuousstrong amplitude seismic reflections.While the braidedmeandering transition pattern showed a combination of vertical and lateral accretion,medium sand content,moderate sandstone thickness,and medium continuousmedium strong amplitude seismic reflections.Meandering subaqueous distributary channels were characterized by lateral accretion,low sand content,minimal sandstone thickness,weak continuous-weak amplitude seismic reflections,and mud-rich inversion features.The primary control factor influencing the transition of river patterns in these channels was identified as the long-term base-level cycle,shaped by paleotopography and sediment supply.Braided subaqueous distributary channels emerged as the main exploration interval for structural prospects,serving as lateral high-speed migration pathways.Dendritic braided and meandering transition intervals were deemed favorable for both structure-lithologic prospects and the expansion of new exploration fields and layers.
基金supported by National Special Research and Development Fund Project(2017YFC0406104)Geological Investigation Project of Ministry of Land and Resources (DD20160300 and DD20160302)+1 种基金Guangxi Natural Science Fund Project (2016JJA150091)Special Fund for Charity Industry of Ministry of Environmental Protection (2016A101)
文摘Investigation of groundwater pollution has been carried out on multiple typical karst underground river systems in recent years in order to reveal the characteristics and mechanism of underground river pollution. Through the summary of the survey results, five characteristics of underground river pollution have been revealed, including directionality, weak hysteresis, easier for reversibility, linear and intermittent(or seasonal); combining with karst geomorphic types, pollution sources(primordial, secondary pollution and compound), pollution ways and pollution receptors, three basic pollution patterns of the underground river were depicted: Recharge area pollution, runoff area pollution and discharge area pollution. At the same time, the study discloses the reality of the underground river pollution is the three basic patterns and their subgenera in combination with super imposition on the space and time. And from the angle of the hydrogeological model, the study expounds the process of underground river pollution. Finally, the study gives naming rules of pollution pattern of the underground river and sets up PISAB method of pattern recognition. The results provide scientific basis for pollution repair and management of underground river in the southwest karst region.
基金supported by the Foundation of Director of Institute of Remote Sensing and Digital Earth,Chinese Academy of Sciences(Y4SY0200CX)the Special Project on High Resolution of Earth Observation System for Major Function Oriented Zones Planning(00-Y30B14-9001-14/16)
文摘The three-river source region (TRSR, including Yangtze, Yellow and Lancang rivers), located in the Qinghai-Tibetan Plateau, China, is a typical alpine zone with apparent ecosystem vulnerability and sensitivity. In this paper, we introduced many interdisciplinary factors, such as landscape pattern indices (Shannon diversity index and Shannon evenness index) and extreme climate factors (number of extreme high temperature days, number of extreme low temperature days, and number of extreme precipitation days), to establish a new model for evaluating the spatial patterns of ecosystem vulnerability changes in the TRSR. The change intensity (CI) of ecosystem vulnerability was also analyzed. The results showed that the established evaluation model was effective and the ecosystem vulnerability in the whole study area was intensive. During the study period of 2001–2011, there was a slight degradation in the eco-environmental quality. The Yellow River source region had the best eco-environmental quality, while the Yangtze River source region had the worst one. In addition, the zones dominated by deserts were the most severely deteriorated areas and the eco-environmental quality of the zones occupied by evergreen coniferous forests showed a better change. Furthermore, the larger the change rates of the climate factors (accumulative temperature of ≥10°C and annual average precipitation) are, the more intensive the CI of ecosystem vulnerability is. This study would provide a scientific basis for the eco-environmental protection and restoration in the TRSR.
基金Project supported by the Ministry of Science and Technology of China, No.2009BAH50B01No.2008BAK50B05
文摘The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR＇s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR＇s courses into two periods, and proposes its changing pattern; concludes the character- istic of diversion points of courses shift events; calculates the velocity of courses shifts, gra- dient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types： the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipita- tion and human activities.
基金National Natural Science Foundation of China,No.41501593,No.41601592National Program on Key Research Project,No.2016YFA0602500
文摘The question of how to generate maximum socio-economic benefits while at the same time minimizing input from urban land resources lies at the core of regional ecological civilization construction. We apply stochastic frontier analysis （SFA） in this study to municipal input-output data for the period between 2005 and 2014 to evaluate the urbanization efficiency of 110 cities within the Yangtze River Economic Belt （YREB） and then further assess the spatial association characteristics of these values. The results of this study initially reveal that the urbanization efficiency of the YREB increased from 0.34 to 0.53 between 2005 and 2014, a significant growth at a cumulative rate of 54.07%. Data show that the efficiency growth rate of cities within the upper reaches of the Yangtze River has been faster than that of their counterparts in the middle and lower reaches, and that there is also a great deal of ad- ditional potential for growth in urbanization efficiency across the whole area. Secondly, results show that urbanization efficiency conforms to a ＂bar-like＂ distribution across the whole area, gradually decreasing from the east to the west. This trend highlights great intra-provincial differences, but also striking inter-provincial variation within the upper, middle, and lower reaches of the Yangtze River. The total urbanization efficiency of cities within the lower reaches of the river has been the highest, followed successively by those within the middle and upper reaches. Finally, values for Moran＇s / within this area remained higher than zero over the study period and have increased annually; this result indicates a positive spatial correlation between the urbanization efficiency of cities and annual increments in agglomeration level. Our use of the local indicators of spatial association （LISA） statistic has enabled us to quantify characteristics of ＂small agglomeration and large dispersion＂. Thus, ＂high- high＂ （H-H） agglomeration areas can be seen to have spread outwards from around Zhejiang Province and the city of Shanghai, while areas characterized by ＂low-low＂ （L-L） patterns are mainly concentrated in the north of Anhui Province and in Sichuan Province. The framework and results of this research are of considerable significance to our understanding of both land use sustainability and balanced development.
基金supported by the Open Fund for Field Stations of Institute of Geographic Sciences and Natural Resources Research,CAS and the Ocean Public Welfare Scientific Research Project(Grant No.201105020)
文摘The influence of anthropogenic activities,especially artificial dykes,on the coastal wetland landscape is now considered as a serious problem to the coastal ecosystem.It is important and necessary to analyze changes of coastal landscape pattern under the influence of artificial dykes for the protection and management of coastal wetland.Our study aimed to reveal the quantitative characteristics of the coastal wetland landscape and its spatial-temporal dynamics under the influence of artificial dykes in the Yellow River delta(YRD).It was analyzed by the methods of the statistical analysis of landscape structure,five selected landscape indices and the changes of spatial centroids of three typical wetland types,including reed marshes,tidal fiats and aquaculture-salt fields.The results showed that:(1)Reduction of wetland area,especially the degradation of natural wetlands,had been the principal problem since the dykes were constructed in the YRD.The dykes created conditions for the development of artificial wetlands.However,the new born artificial wetlands were still less than the vanished natural wetlands.(2)Compared with the open area,the building of artificial dykes significantly speeded up the changes of landscape patterns and the aggravation of the landscape fragmentation in the closed area.(3)The changes of area-weighted centroids of three typical wetland landscapes were greatly affected by dykes,and the movement of the centroid of the aquaculture-salt field was very sensitive to the dykes constructed in the corresponding period.
基金Human Geography provincialkeystonesubjectofHenan University
文摘Agricultural landscape along the riparian zones is designated as important landscape components for partly controlling water quality, biodiversity, as well as for their aesthetic role in landscapes. Therefore, the change of agricultural landscape along the riparian zones is at the top of the agenda for many policy makers and landscape planners. As a basis for conservation management, sufficient information about landscape structure should be provided. In the present study, we reconstructed the former landscape structure and elucidated the changes in landscape patterns during a period of about 15 years. Two sets of maps were used： a landsat-5 TM image （1987） and landsat-7 ETM image （2002）. The frequency index, landscape diversity index and landscape fragmentation index were calculated for analyses. The results showed that： （1） the areas of the irrigated land, river, forest and beach landscape classes presented a decreasing trend while the areas of landscape classes of pool, paddy fields, dry land and construction land increased. （2） Disturbed by human activity, landscape diversity index increased but landscape fragmentation index decreased. In short, Human activities have had important influences on agricultural landscape of the riparian zones along the Yellow River in Henan Province.
基金Under the auspices of National Key Research&Development Program of China(No.2017YFC0505901,2017YFA0604904)
文摘The Yellow River Delta wetland is the youngest wetland ecosystem in China's warm temperate zone. To better understand how its landscape pattern has changed over time and the underlying factors responsible, this study analyzed the dynamic changes of wetlands using five Landsat series of images, namely MSS(Mulri Spectral Scanner), TM(Thematic Mapper), and OLI(Operational Land Imager) sensors in 1976, 1986, 1996, 2006, and 2016. Object-oriented classification and the combination of spatial and spectral features and both the Normalized Difference Vegetation Index(NDVI) and Normalized Difference Water Index(NDWI), as well as brightness characteristic indices, were used to classify the images in eCognition software. Landscape pattern changes in the Yellow River Delta over the past 40 years were then delineated using transition matrix and landscape index methods. Results show that: 1) from1976 to 2016, the total area of wetlands in the study area decreased from 2594.76 to 2491.79 km^2, while that of natural wetlands decreased by 954.03 km^2 whereas human-made wetlands increased by 851.06 km^2. 2) The transformation of natural wetlands was extensive: 31.34% of those covered by Suaeda heteropteras were transformed into reservoirs and ponds, and 24.71% with Phragmites australis coverage were transformed into dry farmland. Some human-made wetlands were transformed into non-wetlands types: 1.55% of reservoirs and ponds became construction land, and likewise 21.27% were transformed into dry farmland. 3) From 1976 to 2016, as the intensity of human activities increased, the number of landscape types in the study area continuously increased. Patches were scattered and more fragmented. The whole landscape became more complex. In short, over the past 40 years, the wetlands of the Yellow River Delta have been degraded, with the area of natural wetlands substantially reduced. Human activities were the dominant forces driving these changes in the Yellow River Delta.
文摘Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversity. The river-lake relationship between Mekong River and Tonle Sap Lake is unique and has always been a major focus in the international community. The land terrain and under-water topography were used to analyze the morphological characteristics of Cambodia Mekong Delta and Tonle Sap Lake. Long series of hydrological data of river-lake controlling stations were used to analyze the water level variation characteristics and water volume exchange pattern between Mekong River and Tonle Sap Lake, and the response relationship to river-lake morphological characteristics were also researched. The results show that: Cambodia Mekong Delta and Tonle Sap Lake Area is low-lying and flat with gentle channel gradient and water surface gradient, making the relationship between water level and area (or volume) smooth. The channel storage capacity of Mekong River and Tonle Sap River is not enough compared to the inflow, so vast flooding plain is extremely prone to be inundated, making the flood relationships between the left and right banks become very complicated. Tonle Sap Lake is a seasonal freshwater lake with water flowing in and flowing out, and the timing and intensity of water exchange with Mekong River are closely related to the water flow resistance at the exit section of Tonle Sap Lake and the cross-sectional area of Tonle Sap River, which can be reflected by the river-lake water level difference and the water level of Tonle Sap River. Affected by the river-lake morphological characteristics, the water exchange intensity between Mekong River and Tonle Sap Lake is great. Tonle Sap Lake not only stores 14.4% of flood volume (39.7 billion m3) from the Mekong River every year, but also supplies 29.7% of dry water (69.4 billion m3) to the Mekong River. Influenced by the adjustment of the floodplain, the water level fluctuation of Mekong River and Tonle Sap Lake is slow, and the rising and droop rates of water level are positively correlated with the floodplain storage area. The research results will help to understand the relationship mechanism between Mekong River and Tonle Sap Lake and provide a scientific basis for the comprehensive governance of Cambodia Mekong Delta and Tonle Sap Lake Area.
基金National Natural Science Foundation of China(No.41671132,41771139)Natural Science Foundation of Jiangsu Province(No.BK20171516)
文摘This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite network projection from an IFFS firm-city data source, we mapped three IFFS networks in the YRD in 2005, 2010, and 2015. A range of statistical indicators were used to explore changes in the spatial patterns of the three networks. The underlying influence of marketization, globalization, decentralization, and integration was then explored. It was found that the connections between Shanghai and other nodal cities formed the backbones of these networks. The effects of a city's administrative level and provincial administrative borders were generally obvious. We found several specific spatial patterns associated with IFFS. For example, the four non-administrative centers of Ningbo, Suzhou, Lianyungang, and Nantong were the most connected cities and played the role of gateway cities. Furthermore, remarkable regional equalities were found regarding a city's IFFS network provision, with notable examples in the weakly connected areas of northern Jiangsu and southwestern Zhejiang. Finally, an analysis of the driving mechanisms demonstrated that IFFS network changes were highly sensitive to the influences of marketization and globalization, while regional integration played a lesser role in driving changes in IFFS networks.
基金International Science ＆ Technology Cooperation Program of China, No.2011DFA20820 No.2011DFG93160+1 种基金 Tsinghua University, No.20121080027 National Natural Science Foundation of China, No.51209010 Acknowledgments We would like to thank Professor Huang Heqing for his helpful guidance in finalizing the paper.
文摘The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as： anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess ahd interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anas- tomosing reaches have a relatively high bed slope （0.86‰） and coarser sediment bed material （d50 = 3.5 mm）. In contrast, meandering reaches have a low slope （0.30‰） and fine sediment bed material （d50 = 0.036 mm）. The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength （i.e. cohesive versus non-cohesive versus channel boundaries）. Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers （Baihe and Heihe rivers respectively）. Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.
基金Prominent Youth Science Foundation of Henan Province No.0003+2 种基金 No.9920 Natural Science Foundation of Henan Province No. 0111070100
文摘Based on the information from forest resources distribution maps of Luoning County of 1983 and 1999, six indices were used to analyze spatial patterns and dynamics of forest landscapes of the typical region in the middle of the Yihe-Luohe river basin. These indices include patch number, mean patch area, fragment index, patch extension index, etc. The results showed that: (1) There was a rapid increase in the number of patch and total area from 1983 to 1999 in the study area. The fragment degree became very high. (2) The area of all the forest patch types had witnessed great changes. The fractal degree of each forest patch type became big from 1983 to 1999. The mean extension index of Robinia pseudoacacia forest, non-forest, shrub forest, sparse forest, and Quercus species forest increased rapidly, but that of economic forest became zero. The fractal dimension each showed that forest coverage has been promoted. (3) The changes of landscape patterns were different in different geomorphic regions. From 1983 to 1999 the vegetation cover area, the gross number and the density of patch, diversity and evenness of landscape were all reduced greatly in gullies and ravines, but the maximum area and the mean area of patch types were increased. In hilly region, both the forest cover area and the number of patch increased from 1983 to 1999, but the mean area of patch was reduced greatly. In mountain region, even though the area under forest canopy reduced from 1983 to 1999, the patch number was increased greatly, the mean area of all patch types was reduced, the extension index, diversity index and evenness index of landscape were all increased. Furthermore, because of different types of land use, human activity and terrain, the vegetation changes on northern and southern mountain slopes were different. According to these analyses, the main driving forces, such as the policies of management, market economy, influence of human activities etc. are brought out.
基金supported by the National Natural Science Foundation of China(Grants No.51379058,51379060,and 51479064)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD Project)the Fundamental Research Funds for the Central Universities(Grants No.2016B06714 and 2014B07814)
文摘Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria were determined. Four flow patterns were identified: mixed, locally unstable, continuously stratified, and two-layer flow. Temperature distributions of the four types of flow patterns were analyzed and compared.The critical Froude numbers for unstable flow, FDcr1, and stable flow, FDcr2, were determined to be 6 and 1, respectively, and comparison of FDcr1 and FDcr2 to the peak Froude numbers, FD1 at the outer bank and FD2 at the inner bank along the anabranch, allowed the flow patterns to be assessed. Then, a discriminant based on initial Jeffreys-Keulegan stability parameters was established to distinguish the flow stages from twolayer flow to completely mixed flow. It is indicated that the three critical Jeffreys-Keulegan parameters increased with the diversion angle of braided rivers. Results also show that, compared to the stratified flow in straight and curved channels, it was more difficult for braided stratified flow to maintain as two-layer flow, and it more easily became mixed flow. Consequently, empirical expressions for stability criteria of the thermally stratified shear flow in braided rivers are presented.
基金Sponsored by Youth Program of National Natural Science Foundation of China(41401152)Youth Program of Humanities and Social Sciences Foundation of the Ministry of Education(14YJCZH228)+1 种基金Domestic Senior Visiting Scholar Plan of Jiangsu Provincial Higher Vocational Colleges(2015FX036)Outstanding Young Teacher Cultivation Program of Jiangsu Universities and Colleges"Blue Project"
文摘Study on the relationship between landscape beauty and ecological beauty is an important scientifi c problem that refl ects the nature of man-land relation, and current academic researches on this topic are most based on a single perspective. Therefore, this paper took the Confucius Temple–Qinhuai River Scenic Area in Nanjing City as a typical case of urban traditional cultural tourism destination, adopted landscape pattern indexes and balanced incomplete block comparison and evaluation method as the evaluation standards of ecological beauty and landscape beauty, and analyzed the coupling characteristics and rules of landscape pattern and landscape aesthetics. The results showed that(a) The overall landscape of the study area had higher fragmentation degree, but different landscape groups were infl uenced by different human interventions, landscape patches showed moderate diversity and heterogeneity, patch area, spatial distribution and spatial aggregation degree showed structural differences.(b) The locals and visitors had aesthetic perception of the study area, but preferred the beautiful natural scenery of the Qinhuai River, as well as the historical buildings and cultural landscapes that contain rich memories of the city.(c) Landscape pattern and landscape aesthetics showed coupled complementation and harmonious coexistence. The Confucius Temple–Qinhuai River Scenic Area has profound historical and cultural background, but it has witnessed gradual loss of cultural characteristics and fast "delocalization" against the background of rapid urbanization. As an urban traditional cultural tourism destination, it carries the responsibility of protecting city memories and inheriting regional cultures.
基金National Natural Science Foundation of China, No.41001008 No.51209010+1 种基金 International Science ＆ Technology Cooperation Program of China, No.2011DFA20820 No.2011DFG93160Acknowledgements Gary Brierley gratefully acknowledges support from a Visiting Professorship awarded by the Chinese Academy of Sciences.
文摘The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections （I, II and III） based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined （some reaches partly-confined） valleys while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections （sections I-V） based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined （some short reaches partly-confined） valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief （elevation, gradient, aspect, valley alignment and confinement） of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.
