Compared with manufacturing industry, the research on producer services is not systematic and comprehensive enough at present. The theoretical reasoning and descriptive analysis based on agglomeration phenomenon are relatively common, but the empirical research to explore the impact of factors is relatively less, and the research considering about market potential in the perspective of new economic geography is even less. Therefore, this article takes producer services of Chinese prefecture-level cities as research objects, and using the panel econometric model to research the relationship between producer services’ market potential and its spatial distribution. Based on the panel data of 285 prefecture-level cities from 2003 to 2012, this article focuses on the spatial distribution of China’s producer services and its market potential, and uses panel model to empirically test the influence of producer services’ market potential on its spatial distribution. The main conclusions are: First, producer services mainly clusters in regional central cities, and the development gap of producer services between central city and non-central city is growing wider; market potential of producer services is mainly distributed in the eastern coastal areas, and dynamically the gap of producer services’ market potential between eastern regions and central and western regions is narrowing. Second, producer services’ market potential has significant positive impacts on its spatial distribution. In terms of producer services divisions, market potential has impacts on spatial distributions of all producer services divisions except financial services and technology services, and the greatest impact falls on business services. Third, in terms of different areas, potential market drives the development of producer services in regional central cities, but the driving effects in non-central cities are not significant, the market potential could not be effectively translated into real demand. Furthermore, this article puts forward some suggestions that in the future, China should raise the level of market potential of producer services in non-central cities to drive the development of their producer services, and especially improve the level of localized professional services in these areas, in order to meet the demand of professional services which has been restricted by distance from the central city in the process of industrial transformation and upgrading.
The Changjiang River Economic Zone is the second largest economy belt, followed Chinese coastal economic regions, which has the most competitive and the great development potential. The development of Changjiang River Economic Zone plays the important exemplary role and is strategically significant for regional harmonious development, new urbanization construction and ecological civilization construction in China. The analysis on the economic network evolution of the Changjiang River Economic Zone can effectively grasp the stage of regional development and make up urban and regional developmental strategy. With the aid of UCINET and ArcGIS, this article analyzed the evolution of economic network and its driving mechanism from density, centralization, “core-edge” structure and QAP (Quadratic Assignment Procedure) analysis based on economic construction data of city during 1988-2012. The result shows that: economic contacts’ network structure tends to be mature, cities’ inner cohesion enhances in three sub-zones, difference continues to narrow between sub-zones, and economic network develops to be balanced gradually. Network degree continues to decline, shows the tendency of many cores and forms the spatial pattern which contains three "highland", one "highland interlocking region" and one "low interlocking region". The areas with high value of betweeness centrality have an obvious grade feature which experiences three phases: equilibrium, non-equilibrium and relative balance. The core-edge analysis shows that the difference of cities’ individual core-degree tends to decrease and the zone shapes plate pattern with high core-degree. The city with high core-degree has a change from “Big size but little” to “Small size but more”. The “core-edge” structure of economic network was divided into many blocks which include the middle-lower reaches and the upper reaches of the Changjiang River. There has many core-cities formed in each block and the number of isolated cities rapidly reduces in the economic network. Economic ties remain to be strengthened between the two blocks. The economic network characteristic is roughly consistent with the situation of economy development pattern in the Changjiang River Economic Zone. The QAP (Quadratic Assignment Procedure) analysis shows that many factors drove economic network to evolve and optimize which contains transportation way’s innovation, economic elements agglomeration and diffusion and construction of urban agglomeration, economic globalization, etc.
Integrating urban and rural development is the strategy and mostly significant task of people-oriented urbanization. It is of importance to strengthen research on urban-rural coordinated development, to provide scientific supports for urban-rural planning and policy making. We first proposed the theoretical framework of urban-rural coordinated development and established coordinated index system. Then, by GIS and ESDA methods, spatial patterns and characteristics of urban-rural coordinated development were explored, and its influencing factors were analyzed based on spatial econometric model. The results are shown as follows: 1）The urban-rural coordinated development system consists of four subsystems, which are factors, structures, functions and policies. The coordinated urban-rural development depends on the mutual coordination and cooperation of elements within the subsystem and positive mutual feedback evolvement among the subsystems. 2） Sub-indices such as investment, industry, income and consumption between urban and rural areas take on significant spatial differences, respectively. The degree of variation of investment coordination index, industry coordination index, income coordination index and consume index reduces in turn. 3） Urban-rural integrated coordination index shows obviously spatial differences among the east, middle, northeast and west of China, and takes on spatial agglomeration. High-level areas of coordination index gather in the eastern coastal region and a few cities in the central and western China, while low-level areas are mostly located in the central and western China, especially showed in the provincial map. 4) Economic growth, urbanization, rural investment and domestic consumption had significantly positive effects on urban-rural coordination development, while urban investment had negative effects. Meanwhile, education investment, education level and infrastructure did not have significant effects due to the misallocation of resources between urban and rural areas. These findings are of use to integrate urban and rural development in different aspects. Firstly, we should appropriate urbanization models should be explored in different areas according to the areal characters and its urban-rural development transformation status. Secondly, it is essential for the Chinese authorities to change its traditional planning model and implement rural revitalization plan, especially improving rural infrastructure construction, public services and the comprehensive function of the town. Thirdly, we should reform binary urban and rural managing system gradually and moderately, according to taking a sufficient consideration of the status and trend of inside and outside urban-rural coordinated systems.
The State Council Leading Group Office of Poverty Alleviation and Development ever defined the 14 concentrated contiguous areas with particular difficulties in China as a crucial battleground for poverty alleviation. Basing on the road network in 1980, 1995 and 2010, this article elaborates the evolution of road network and road accessibility of the 14 concentrated contiguous areas with particular difficulties in China quantitatively, explores the spatial pattern evolution trend of road accessibility of the 14 concentrated contiguous areas with particular difficulties in China through spatial autocorrelation analysis. The results indicates that the road network structure of the 14 concentrated contiguous areas with particular difficulties in China optimized continuously from 1995 to 2010, and the merit rating kept a steady inheritance. The network accessibility of the 14 concentrated contiguous areas with particular difficulties in China improved at different levels from 1980 to 2010, also the merit rating of network accessibility of the 14 concentrated contiguous areas with particular difficulties in China kept steadily. Luoxiao mountainous areas, Lüliang mountainous areas and Dabie mountainous areas etc. got a relatively well situation on raster accessibility, but Tibet, Tibetan areas of four provinces and southern three states in Xinjiang are just the opposite. Then, according to the spatial agglomeration relationship of network accessibility of the 14 concentrated contiguous areas with particular difficulties in China from 1980 to 2010, this article divides the evolution treads of accessibility spatial pattern of the 14 concentrated contiguous areas with particular difficulties in China into 3 types, which are “maintaining the same”, “tending to agglomeration”, and “tending to equilibrium”. It summarizes road network characteristics and temporal and spatial pattern of accessibility evolution, explores some rules of road accessibility of the 14 concentrated contiguous areas with particular difficulties in China, not only enriches the study of accessibility evolution in poverty-stricken areas, but also provides some reference for our country to develop road traffic in poverty-stricken areas.
In the background of the globalization and information economy era, a region’s innovation capacity is increasingly becoming the determinant of competitive advantage. Regional innovation performance is an important aspect of regional innovation capacity. Measuring its spatio-temporal evolution characteristics and finding influencing factors have important theoretical and practical significance to develop innovation strategies, improve innovation efficiency and optimize innovation environment. Building innovation input and output evaluation index systems, the article selects innovation output quantity and innovation efficiency to present regional innovation performance. Then the article analyzes the spatial distribution and regional differences of innovation performance since 2004. There are four main findings. First, the high value areas of innovation performance are eastern coastal zone and the region along the Changjiang River, which coincides with T-shaped structure of land development. Second, polarization of regional innovation performance has increased obviously since 2004, and the gap of innovation capability between western region and the eastern region grows. Third, the regional difference of innovation output is the largest, and the innovation efficiency is the smallest. Third, regional differences of innovation input and innovation output tend to increase, and innovation performance and innovation efficiency’s regional differences show a decreasing trend at first and then increase slowly. Furthermore, we investigate the factors including regional innovation basis, the industrial cluster environment, the quality of research linkages, government supporting and technology spillover that affect the regional innovation performance. Then we conduct regression analysis to examine the relationships between regional innovation performance and nine influencing factors. The result reveals that regional innovation basis and government supporting influence regional innovation performance most, and then the quality of research linkages follows. The industry cluster environment and technology spillover impact on regional innovation performance less. Finally, some policy recommendations are put forward to raising regional innovation capability. The region should continue to increase the technical innovation input, especially provinces with the better foundation should play a leading role in innovation, and the national policies should be inclined to the western and middle regions. Government should strengthen the role of policy supporting and macro-control, rather than a major investment of innovation, and encouraging enterprises become the innovation subject. Furthermore, we should optimize the industrial cluster environment which can provide a good environment for regional innovation.
Vulnerability assessment is an important method to reveal the economic development "bottleneck" factors, and has great significance to analyze the major restricted factors to achieve economic development. Based on a detailed description about the vulnerability of marine economic system (MESV), the article establishes a vulnerability assessment model of marine economic system in China from the aspects of sensitivity and response capacity. Then it combines the methods of set pair analysis and vulnerability assessment, and uses combination weight method to evaluate the indicators and to calculate their weights, then analyzes the evolution trends and major influencing factors of vulnerability in marine economic system from 1996 to 2012. At last, it puts forward corresponding development countermeasures. The results indicate that the vulnerability in marine economic system of China during the past 17 years, shows a declining trend, and the sensitivity to adverse disturbance takes on a declining trend and response capacity sometimes presents a wandering period, sometimes in a growth phase for internal and external shocks. The MESV has two characteristics: 1) the MESV declined rapidly in 1996-2001, 2005-2006, and 2008-2010; 2) the MESV showed little change, more stable in 2001-2005, 2006-2008, and 2010-2012. The evolution of sensitivity can be divided into two stages: decreased obviously form 1996 to 2002, fluctuating frequented from 2002 to 2012. The evolution of response capacity fluctuated slightly in 1996-2002 and 2008-2012, and then went up steadily from 2002 to 2012. The influence of sensitivity plays a leading role to the vulnerability in marine economic system of China among the sensitivity, response capacity and vulnerability by using regression analysis. It suggests that in improving response capacity and reducing the vulnerability in marine economic system of China, the style of economic growth should be changed, including controlling over-exploitation and rational utilization of marine resources, developing science and technology and cultivation of talents. At the same time, it is also important to strengthen marine of pollution and to control environmental protection measures.
Crime hotspot mapping can forecast the occurrence of potential offense and direct the police activities to restrain the offense by revealing the spatial pattern of the offense. Density estimation usually presents the most significant outcome of the potential offense among all the hotspot mapping methods, for the street crimes in particular. Compared with the density estimation algorithm without the spatial or temporal near similarity, the temporal near similarity, spatial near similarity and spatio-temporal near similarity among offense points were illustrated in this article. With street robbery data of DP Peninsula during the period from 2006 to 2007, four different crime hotspot maps based on non-spatial-temporal near similarity, spatial near similarity, temporal near similarity and spatial-temporal near similarity were produced respectively. Moreover, with the validation data of 2008 cases,two different classification methods, Natural breaks (Jenks) classification and Equal proportional selection by area were utilized to delimit the hot area and then the comparisons among the scores of the Prediction Accuracy Index (PAI) of those four different crime hotspot maps were implemented. The results presented that the density estimation method based on the spatial-temporal near similarity holds significant advantages when predicting the potential offences.
The comprehensive level of new urbanization in 285 prefecture level cities of 2003-2012 was measured, and the spatial pattern of its evolution was analyzed. Based on reverse distance square weight matrix, this article tested the spatial correlation, established the spatial econometric model to analyze its influencing factors. The conclusions were as follows: in general, the spatial pattern of new urbanization showed a decreasing trend from east to west, continuously expanded to the inland area, and the level of big cities obviously was higher than the small and medium-sized cities; new urbanization level of cities had obvious spatial autocorrelation. Labor, investment, economic development, government capacity, infrastructure and industrial structure all played positive roles in promoting new urbanization. Economic development, labor and infrastructure had a positive and significant spatial spillover effect, the others showed a negative spillover. SDM model revealed that the local explanatory variables and surrounding areas variables affected new urbanization. Based on this, this article put forward some specific policy recommendations for new urbanization in China to provide a theoretical basis.
Regional industrial cluster and its transfer are significant which promote regional development. Then, the cluster transfer and regional development exist an interactive coupling relationship. By the refinement of industrial chain, industrial cluster transfer which has a different space path appears such increasing obvious trend. In the case of Jiangsu Province, according to the industry-relativity, this article divides the labor-intensive industries into four types, then, uses Gini coefficient, econometric model and the method of horizontal comparison and vertical comparison to analyze the trend of agglomeration and diffusion. According to the analysis of the industries current situation in Jiangsu Province, it shows that the tendency of labor-intensive industrial cluster transfers credibly. Compared with the decline status of the type I and II labor-intensive industries in the southern Jiangsu, there is a rapidly increase in the northern and central Jiangsu. In addition, the redistribution of the type III of labor-intensive industries mainly happens in the southern Jiangsu. In general, there is still a wide difference in distribution of labor-intensive industries in Jiangsu Province. And the higher industrial relevancy is the more distribution differences will be. Based on the analysis of measurement model, the conclusion is drawn that Xuzhou, Huaian, Lianyungang and Suqian are suitable for undertaking the type I labor intensive industry from the southern Jiangsu, the type II is fit to be accepted in Nantong, Huaian, Yancheng and Yangzhou, and Xuzhou, Yangzhou, Nantong and Zhenjiang are suitable for the development of the type III. Furthermore, the researches on labor cost from different regions objectively verified the reliability of above-mentioned conclusions. The conclusion shows that labor intensive industry cluster transfer in Jiangsu presents a center periphery structure outward from the South, follows three ladder that South as transfer center and North as undertaking periphery and "one center, two wings, one hinterland" cluster transfer path. Finally, the article concludes the law of space path by center-periphery theory, and gives some suggestion to balance the regional development.
Using the demographic data of fifth and sixth census, this paper analyzes the population redistribution in Nanjing metropolitan area from 2000 to 2010 and tries to find some laws. Firstly the authors analyze the general characteristics of population redistribution in metropolitan area, and finds that each area has experienced a population growth in the past ten years, while the population of suburb area increased the most. We also find that the population gravity center has been moving to the south gradually, and the core area of population distribution has the tendency of shrink inwards. Then we analyze the population redistribution of Nanjing metropolitan area with mathematical models. Based on the synthetic judgment of determination coefficient R2, F-criterion and curve image analysis, the lognormal model is the optimal choice to reflect the monocentric structure. The model curves’ changes indicate that suburbanization was still concentrated in the suburb area last ten years. The analysis of polycentric model illustrates that a polycentric structure has been formed initially in Nanjing metropolitan area, but the population still concentrates to the main center prominently, which is different from other Chinese cities. Both the polycentric and monocentric models have good fitting results reflects that the polycentric structure is not ripe yet compared with western cities. The analysis of population spatial variability reflects that the population heterogeneity has increased and population distribution is more and more complicated, both of which illustrate that the metropolitan area has been developing to a higher stage. On the basis of keeping the urban center livable and efficient through moderate aggregation, guiding people moving to the suburb and making the city form ripe polycentric structure may be the optimal way to develop the large cities of China in the future.
The article defined the connotation of different transition stages and identification system of resource-based cities in Jilin Province, then introduced Piecewise function method to identify the transition stage, and analyzed the character. The result showed that, economic and social development, infrastructure construction, environmental governance improved well, and the transition of resource-based cities overall stepped into the fundamental stage. Among all indicators, economic transition effect was the best, but the infrastructure transition effect lagged behind. While the results differed obviously between different types of resource-based cities, the transition effect of oil cities was much better than forestry and coal cities, and the resource-exhausted cities were confronted with much more difficulties than others in the process of transition. Meanwhile, the resource characteristics of resource-based cities were still prominent. In general, the results coincided with the actual situation of Jilin Province. Then the article analyzed the causes of the transition of the resource-based cities from the central government policies, industrial base and spatial location, natural resources, local financial, etc. Finally, the study proposed sustainable development routes and modes of resource-based cities in Jilin Province. For example, the coal, metal, and oil cities can choose the transition routes such as comprehensive development mode, dominant industry transition mode, and continuous industry mode, while the comprehensive and forestry cities may choose the turn direction routes such as sustainable resource dived mode.
Motivation is an important factor that determines behavior and the relationship between tourism motivation, destination choice is the key to forecast the future travel model. In the Changjiang River Delta Region, with the rural residents’ income and consumption level increased and the willingness to travel strengthened, understanding the tourism motivation and its influence on tourism destination choice is significant for this region’s tourism market development. Taking the Changjiang River Delta Region for example, this research analyzes tourism motivation of rural residents with the method of principal component analysis by dividing 24 motivation variables into 5 factors. And it studies how these motivations influence the choice of six tourism destination such as “the modern big city”, “small city”, “historical and cultural city”, “tourist town”, “mountainous area” and “rural areas” by building logarithmic regression equation. The destination choice is the key to forecast the future travel model. The results show that: 1) Tourism motivations of rural residents in the Changjiang River Delta are mainly based on the sightseeing level. 2) the rural residents in the Changjiang River Delta agree with lower perception of tourist motives of visiting relatives and friends, but visiting relatives and friends has influence on the choice of different destinations. 3) the rural residents in the Changjiang River Delta have a strong desire to promote its position in the family, relatives, friends by tourism. 4) the tourism safety is very important to improve rural residents, tourism, at the same time rural residents pay attention to the tourism destination accommodation facilities to build home outside of the home feeling.
The impacts of climate change on hydrological processes in Tibetan Plateau are complicated and sensitive, and the resulting water resource change could have profound influences. Nujiang River, sourcing from Tibetan Plateau, is an important international river in southwest China. Taking use of long term records, air temperature and precipitation variations in the middle and upper Nujiang River Basin during 1960 to 2009 were analysed. On the other hand, seasonal flow, extreme flow, and flow duration curve in Daojieba station were compared to study the variation characteristics of low flow and their responses to climate change in recent 50 years. The results show that winter and spring air temperature had increased, and the rate in winter was higher than that in spring, which increased with altitude. In Naqu station in the river source, the increasing rate of winter temperature could reach 0.81℃/10 a. In addition, daily minimum air temperature in winter and spring in the middle and upper Nujiang River Basin had increased more quickly and significantly than daily maximal air temperature, which showed that increasing mean temperature was largely due to rising nocturnal temperature. The trends of winter and spring precipitation were both increasing. The increasing rate of spring precipitation in Naqu, Suoxian, and Dingqing stations were between 6.5 and 7.7 mm/10 a, and spring precipitation in these 3 stations in 2000 s were 54.4%, 35.6%, and 18.0% more than the average value. Winter and spring flows in Daojieba station had increased significantly, and the increasing rate were 18 and 44 (m3/s)/10 a, respectively. Winter flows in 1990s and 2000s were 7.3% and 10.7% higher than the average value, while the anomaly of spring flow in 1990s reached 16.8%. On the other hand, whether annual minimum of 1-day, 7-day, 30-day, and 90-day moving average flows, or Q75, Q90, and Q95, the value in 1990s and 2000s were all much higher than those in other decades, which showed that low flow had increased from 1990s. For instance, between 1960 and 2009, there were 10 years with minimum daily flow greater than 400 m3/s, which were all in 1990s and 2000s. While 20 years with minimum daily flow less than 350 m3/s, among which only 2 years were in 1990s and 2000s. In addition, Q75 in Daojieba station in 1960s, 1970s, and 1980s were 489, 510, and 488 m3/s respectively. While in 1990s and 2000s, the values were 577 and 563 m3/s, which were 10%-18% higher than previous 3 decades. The increase of low flow in the middle and upper Nujiang River Basin could be attributed to the increasing air temperature and precipitation in winter and spring. At first, increasing precipitation would generate more flow. Secondly, rising air temperature may accelerate melting processes of snow and ice. In addition, frozen soil degradation caused by climate warming could also affect hydrological processes.
Amount of stream water in the Huanghe River has decreased dramatically in the end of 1990s. Researches showed that the runoff dynamics and relationship between runoff and precipitation in sub-basins in the middle reach of the Huanghe River were different according to basin location and time interval. In this arcitle, we investigated the dynamics, anomalies as well as the changing trends of annual precipitation and runoff in the Heshuichuan Basin in the Jinghe River during 1964-2011. In the meanwhile, the possible impacting factors for the evolution trend were explored. Results showed that: 1) Annual precipitation varied from 338.15 mm to 811.2 mm with an average of 525 mm during 1964-2011, both maximum and minimum annual precipitation presented in the 1960s. Annual runoff depth varied between 7.85 mm and 59.52 mm with an average of 17.72 mm. Annual precipitation and runoff decreased during 1964-2011 with a rate of -0.04 mm/a (P=0.52) and -0.10 mm/a (P=0.97), respectively. The turning points for annual precipitation and runoff were different, runoff turned to decrease in 1978, while annual precipitation turned to increase in 2000. 2) Dynamics and changing trend of annual precipitation and runoff in the Heshuichuan Basin were similar to sub-basins of the Jinghe River located in the North and Northeast part. They were also similar to sub-basins of the Huanghe River located in the Southwest part of middle reach (Hekou-Longmen) region. Influenced by many kinds of natural factors and human activity, the hydrologic factors change differently in different geographical position and different size of basin. 3) In the period of 1964-2011, annual rainfall was correlated to runoff with a coefficient of 0.53, suggesting that the overall trend of runoff was dominated by precipitation in this basin. However, the correlation and double mass curve of annual precipitation and runoff varied among time intervals. Rainfall was correlated with runoff during 1964-1978 with a coefficient of 0.75, indicating that the human influences were smaller than precipitation change during this period. The double mass curve of rainfall-runoff deviated downward since 1979 and amplified during 2004-2011, suggesting that the rainfall-runoff relationship had changed due to human activities since1979. This change can be inferred to the enhanced soil and water conservation measures since 1979, as the amount of terraces, backbone dams and check dams were increased. More important, the weaker rainfall-runoff correlation since 2004 can be related to the dramatic land use/cover change caused by the “grain for green” policy.
Marine oil spills from operational discharges and ship accidents always have calamitous impacts on the marine environment and ecosystems, even with small oil coverage volumes. Remote sensing solutions using space-borne or airborne sensors are playing an increasingly important role in monitoring, tracking and measuring oil spills and are receiving much more attention from governments and organizations around the world. Compared to airborne sensors, satellite sensors, with their large extent observation, timely data available and all weather operation, have been proven to be more suitable for monitoring oil spills in marine environments, whilst the latter can be easily used to identify polluters and oil spill types but are of limited use due to costs and weather conditions. Currently, the commonly used satellite SAR sensors for this purpose include RADARSAT-1/2, ENVISAT, ERS-1/2, and so on. The detectability of oil spills by SAR images is based on the fact that oil slicks dampen the Bragg waves on the ocean surface and reduce the radar backscatter coefficient. Unfortunately, many other physical phenomena, for example, low-wind areas, wind-shadow areas near coasts, rain cells, currents, upswelling zones, biogenic films, internal waves, and oceanic or atmospheric fronts, can also generate dark areas, known as look-alikes, in SAR intensity images. Another factor which influences the backscatter level and the visibility of oil slicks on the sea surface is the wind level. Oil slicks are visible only for a limited range of wind speeds. Generally speaking, SAR based oil spill recognition includes three stages: dark spot detection, dark spot feature extraction and oil spill classification. The work in this article focuses on the feature extraction of detected dark spots. The task at this stage involves defining and acquiring the features existing in SAR intensity images, which can be efficiently used in the classification stage to distinguish oil spills from look-alikes. Commonly defined features for this purpose include the geometry and shape of the dark spot area, textures, contrast between dark spots and their surroundings, and dark spot contextual information. To this end, this article presents regional image segmentation for dark spot feature extraction from SAR intensity image, which is completed by Metropolis-Hastings (M-H) and expectation maximum estimate algorithm. To segment a SAR intensity image, it is reasonable to approximate the homogenous regions in an SAR intensity image by Voronoi polygons. The number of Voronoi polygons is assumed unknown. The marine background and dark spot regions, in which the pixel intensities are assumed to follow independent and identical Gaussian distributions, consist of some partitioned sub-regions. On the basis of the image domain partition, the SAR intensity image is statistically modeled by two Gaussian distributions. And then the SAR intensity image segmentation is performed by the M-H and expectation maximum estimate algorithm for extracting the geometries and statistical parameters of dark spots. In order to verify the validness of the proposed method, testing is carried out on simulated and real SAR intensity images. The results from all test images are qualitatively and quantitatively evaluated and show that the proposed algorithm works well on dark spot feature extraction.
Study of the precipitation structure is theoretically and practically important for the development of human understanding of impacts of climate changes on regional hydrological cycle and also for regional water resources management and also for planning and management of agricultural activities and it is particularly true for the Huaihe River Basin, one of the key agricultural product suppliers in China. Flood and drought disasters are serious and prevailing in Huaihe River Basin, so it is important to analyze precipitation changes in terms of process and structure and related causes behind. Based on daily precipitation data from 35 precipitation stations covering the period from 1961 to 2008 in Huaihe River Basin, the spatiotemporal characteristics of precipitation structure are investigated and possible linkage to different ENSO events has been explored. The ENSO events considered in this study are: the Eastern Pacific warm events (EPW), Central Pacific warm events (CPW), and the Eastern Pacific cold events (EPC). The results indicate that: 1) The Yi-Shu-Si Rivers are in drying tendency and precipitation in the Huaihe River is in increasing trend. The NCD increased, while the MCD decreased in the northern Hai River Basin. Besides, significant increase of the ATP is found in the Huaihe River Basin, which may have the potential to trigger increase of downstream streamflow. While the MCD and MCP increased which significantly decreases the precipitation intensity; 2) During the CPW event, MCD and MCP changes are subject to large magnitude and in negative cumulative difference anomaly; During the EPC event, NCD increased significantly when compared with NCD changes in normal years; while the consecutive rainy days are lengthening during EPW event are with decrease of precipitation amount; 3) The heavy precipitation in Huaihe River Basin tends to be intensifying under the influences of ENSO regimes. The heavy rain and rainstorm during different ENSO events are subject to large difference anomaly and the anomaly index can reach + 50%. The EPC and CPW events have the potential to trigger flooding events in Huaihe River Basin, such as 1964, 1991and 1998 when flood occurred. In CPW and EPW events, the number of days with heavy rain and storm is more than that in normal years in Huaihe River Basin, and heavy rain days are less than those in normal years in the Yi-Shu-Si river system; In EPC events, the number of days with heavy rain and storm is less than in normal years in Huaihe River, and heavy rain days are more than in normal years in the Yi-Shu-Si River system: 4) ENSO events have impact on 4-day consecutive precipitation event significantly, and it is particularly the case for 5-day consecutive precipitation events. Precipitation anomaly is greater in EPC event in the Huaihe River Basin than in the CPW and EPW events. The precipitation anomaly index except for 1- and 2-day precipitation, are higher than + 40%. The precipitation anomaly index for 6-day precipitation event is larger than 50% during 5 out of 10 years. Floods with different magnitudes occur during EPC event in Huaihe River Basin and 6-day consecutive precipitation event is subject to the biggest anomaly during CPW event and the anomaly index can reach + 50%. The results of this study can well elucidate changing properties of precipitation events with different durations and also possible causes by analyzing changes of different precipitation events during different ENSO regimes.
The high-accuracy quantitative inversions of foliar nitrogen concentrations in wetland plants from hyperspectral data contribute to make the advanced comprehensions of wetland ecosystem functioning, biochemical processes and nitrogen circles. The study area in this paper was located in the Panjin Shuangtaihekou Wetland National Nature Reserve Administration. The wetland was mainly dominated by phragmites australis (Cav.) Trin. ex Steud with an area of 900 km2. Foliar spectral reflectance data were measured using an ASD spectroradiometer (FieldSpec Pro FR) with a 25° field-of-view (FOV) and a spectral range of 350 to 2 500 nm. Subsequently, sampling reeds at each plot were cut at ground level and sent immediately to the laboratory. The nitrogen concentration of the vegetation was measured using a standard method of the Kjeldahl technique. Based on the different spectral transformation techniques and original spectral data (R), partial least-squares regressions (PLSR) integrating with the bootstrapping approaches were used to develop the prediction models of nitrogen concentrations in reedleaves. The set of spectral transformation techniques used in this study included the water removal (WR), continuum removal (CR), first derivative (FD), and reciprocal-logarithm transformation (LR). The variable importance of projection (VIP) was used as a metric to quantify the important degree of a spectral band for estimating foliar nitrogen concentrations with the various spectral transformation techniques. The results indicated that WR spectral transformation in combination with PLSR estimated foliar nitrogen concentration with the highest accuracy (R2=0.87,RMSE=0.57). The WR approachcan effectively reduce the water absorption effects on the subtle nitrogen absorption features across the fresh leaf spectrum. This study demonstrated the performance of the WR technique in increasing the accuracy of foliar nitrogen estimation for wetland plants. The estimation accuracies achieved from the applications of all spectral transformation techniques were higher compared to the original spectral data. The selected feature bands for estimating foliar nitrogen concentrations from the WR technique were all centered at the shortwave infrared (SWIR) spectral region, and forty percent (40%) of the selected bands from WR were associated with known nitrogen estimation bands. While, the selected feature bands from other spectral transformation techniques were located in both the SWIR and visible near-infrared (VNIR) spectral region. Phenology plays an important role in foliar nitrogen estimation using spectroscopy data. Therefore, there is a need for the future studies for understanding how phenology influences the performance of the WR technique in estimating foliar nitrogen concentrations in wetland plants.
This article focuses on constructing a three-dimensional fractal model to quantify topographic features and analyzes its spatial variation in arsenic rock area. Topographical complexity is commonly described by the fractal dimension, which is a comprehensive index for topography, and a significant parameter for the soil erosion model at the watershed scale. Although lots of fractal models describing topographic features have been built by domestic and overseas scholars, mostare flawed on the model structure. To solve this problem, the article proposes a new index describing relief volume, and designs a new 3D fractal model for arsenic rock area. Based on the fractal model, ESRI ARCENGINE was used to develop the software computing fractal dimension of topographic features. The fractal dimensions of 274 small watersheds were calculated by this software, and their statistical values, such as average value, maximum value, minimum value, standard deviation and coefficient of differentiation,were obtained using zonal statistical tool.The thematic map showing spatial variation was produced using ArcGIS software based on classification statistical method. Finally, the reasons causing the spatial variation of 274 small watershedsfractal dimensions were analyzed in aspects of landform genesis and internal differences in arsenic rock area. The results show that: 1) The 3D fractal dimensions computed by the developed software which was designed in this article can accurately describe the topographical complexity, and the new index is very effective; 2) The 3D fractal dimensions of all small watersheds are between 1.683 6 and 1.948 6 in arsenic rock area; 3) On the whole, the 3D fractal dimensions is largest in the arsenic rock area covered by sands (the average value is 1.796 6 ), the second is the serious and severesoil erosion area in the arsenic rock area covered by the bare sandstone(the average values are 1.785 4 and 1.774 8, respectively), and the last one is arsenic rock area covered by loess (the average is 1.765 9 ). The reasons causing the differentiation of the fractal dimensions are mainly different topographical characteristics due to soil erosionin arsenic rock area.
The Fifth Assessment Report (AR5) was released by the Intergovernmental Panel on Climate Change (IPCC) in 2013, and new observations have further proved that the warming of the global climate system is unequivocal. The influence of natural climate variability and anthropogenic climate change can contribute to disaster, and the integrated risk assessment could increase resilience to the potential adverse impacts of climate extremes. Using daily temperature, relative humidity and precipitation data of meteorological stations in Beijing-Tianjin-Hebei Region and its surrounding areas, this article attempts to describe spatiotemporal clustering characteristics of drought, heavy rain and heat waves during 1960-2013, based on space-time clustering and other analysis method. The results show that: Before the year of 2000, drought and hot waves presented a negative anomaly, and heavy rain was frequently determined in the study area. After the year of 2000, it showed obviously increasing trend for drought and hot waves, the frequency of heavy rain declined significantly. Spatially, synthesized multi-hazard assessment, the southeast coast and western mountainous area were relatively higher risk than the middle plain. Different periods of drought, heat waves and heavy rain in Beijing-Tianjin-Hebei Region had different coupled pattern. Drought and heat waves were highly overlap in northern coastal areas, northern Yanshan Mountains, western Taihang Mountains and southern plain. As for cities like Beijing, Tianjin and Baoding in the middle plains, it was multi-disasters overlapping low risk region, where spatiotemporal clustering of drought, heavy rain and heat waves were relatively little. The gravity center migration of heat wave, drought and heavy rain showed the counterclockwise of spiral change in Beijing-Tianjin-Hebei Region. Before 1980s, the gravity center moved form southwest to northeast coast region; After 1980s, it begun a second counterclockwise migration, drought, heavy rain and heat waves showed the aggregate trend on the middle plain.
Anthropogenic radionuclides (137Cs, 90Sr, and Pu isotopes) released from atmospheric nuclear tests, major nuclear reactor accidents, and other sources can be detected in the environment in most parts of the world. In particular, as a result of atmospheric nuclear explosions, about 15 PBq of 239,240Pu (1 PBq=1015 Bq) and 0.3 PBq of 238Pu have been globally released into the atmosphere. These radionuclides may be useful tracers of environmental changes, such as desertification, erosion and sedimentation processes, in terrestrial regions. Furthermore, measurements of radionuclide deposition are useful for several purposes, including the assessment of the effects of radiation from anthropogenic radionuclides on humans. They may also find use as indicators of environmental events. Most of the current investigations focus on the chemical behaviors such as transfer and diffusion in environment, but for the atmospheric wet deposition of radionuclide Pu, the publically available report is very limited in China. In this article, we investigated and quantified preliminarily the 239,240Pu atmospheric deposition in the Changjiang River Estuary Region based on the records of 239,240Pu atmospheric deposition and precipitation in Tokyo in Japan. The results indicated that 239,240Pu atmospheric deposition history in the Changjiang River Estuary Region was similar to that of the whole north hemisphere. The cumulative atmospheric deposition inventory of 239,240Pu was estimated to be 34.556 Bq/m2 in 1957-2005. The maximum annual deposition occurred in 1963 after the large-scale atmospheric nuclear weapons testing in 1950s-1960s conducted by the United States and former USSR. Annual 239,240Pu deposition decreased in the period from 1963 to 1967 according to the stratospheric residence time of nuclear debris. In the 1970s, the radionuclide deposition observed in the Changjiang River Estuary showed no decrease because of a series of American and Chinese atmospheric nuclear tests. In addition, 239,240Pu atmospheric deposition history in the Changjiang River Estuary Region was similar to that of Tokyo. The results proved that spatial distribution of the cumulative deposition of anthropogenic radionuclide Pu is similar on the same latitude regions of the northern hemisphere and the similar climate conditions.
