In this paper, firstly, in accordance with the principles of the hydrologic cycle simulation, methods commonly used in the runoff yield simulation were analyzed. On this basis, the rainfall-runoff coefficient of correlation, the storage-full runoff and the runoff yield under excess infiltration applied in the runoff simulations, as well as the methods of isochronic hydrograph, unit hydrograph, the Saint-Venant equations, the Muskingum method applied in the flow concentration simulations, and also parametrization methods of topography, land cover, land use and soil type applied in major simulation methods were analyzed and discussed. In addition, the degree of description of the simulation process mechanism by these parametrization methods of watershed topography, land cover, land use and soil types was discussed and the parametrization methods were divided into different categories, namely: the not clearly expressed category, the rating parameters category, the deterministic parameters category and the expressed by physical processes category. Furthermore, the influence of the applied in different parametrization methods topography, land cover, land use and soil types on the hydrologic cycle simulation results was clarified. Finally, returning to the hydrologic models nature, major drawbacks of the simplified description of complex rational and physical mechanisms existing in the underlying surface parametrization methods in hydrologic models were outlined, and also two directions in the future development of those methods in the hydrologic cycle simulations were discussed.
Global warming and climate change are issues that have aroused widespread attention, and the need for a transition to a low-carbon economy has become the consensus of the international community. China has become one of the world's largest energy consumers, as well as one of the biggest emitters of greenhouse gases. This further highlights the importance and urgency of research on carbon emissions from energy consumption. Based on regional perspectives of the impacts of carbon emissions, the analysis of mechanisms responsible for carbon emissions has become an important research topic. Xinjiang, an important Chinese energy production base, is currently going through a period of strategic opportunities for rapid development. It is critical to ensure stable socioeconomic development as well as to achieve energy savings and meeting emission reductions targets, thus the harmonious development of "society-economy-energy-environment," is the key issue currently facing the region. This study, based on the input-output theory, presents a structural decomposition analysis of the factors affecting energy consumption and carbon emissions in Xinjiang from 1997-2007. This analysis employs a hybrid input-output analysis framework of "energy-economy-carbon emissions," and uses an extended IO-SDA model. The data for this study come from the Xinjiang input-output table for 1997-2002-2007. Population, economic, and energy source data are derived from the Statistical Yearbook of the Xinjiang Uygur Autonomous Region. (1) Xinjiang's carbon emissions from energy consumption increased from 20.70 million tons in 1997 to 40.34 million tons in 2007; carbon emissions growth was mainly concentrated in the production and processing of energy resources, the mining of mineral resources, and the processing industry. (2) The analysis of the direct effects of the influencing factors on carbon emissions shows that the change in per capita GDP, final demand structure, population scale, and production structure were the important factors causing an increase in carbon emissions, while the decrease in carbon emission intensity during this period was an important factor in stopping the growth of carbon emissions. This shows that while Xinjiang's economy and population were growing, the economic structure had not been effectively optimized and production technology had not been improved, which results in a rapid growth of carbon emissions from energy consumption. (3) An analysis of the indirect effects of the factors influencing carbon emissions shows that inter-provincial transfers, gross fixed capital formation, and consumption by urban residents had significant influence on the changes in carbon emissions from energy consumption in Xinjiang. (4) The growth of investments in fixed assets of carbon-intensive industry sectors, as well as the growth of inter-provincial transfers of energy resource products, makes the transfer effect of inter-area "implicit carbon" very significant.
In this paper, the Kriging interpolation method was introduced to analyze the spatial distribution characteristics of PM2.5 in Jiangsu province in 2014, and then the evaluation index system for the PM2.5 was constructed, which consists of three index layers and 27 indexes. The grey correlation analysis method was used to explore the correlation between PM2.5 and its influencing factors. Finally, the relationship between the spatial distribution of PM2.5 and the main influencing factors was analyzed. The conclusions can be drawn as follows: (1) The PM2.5 in the coastal areas and the north is lower, while it is higher in the inland areas and the south. (2) The weight of PM2.5 pollution sources index layer is the largest (wi = 0.4691), the weight of the air quality index and meteorological elements layer is larger (wi = 0.2866), and the weight value of urbanization and industrial structure index layer is the minimum (wi = 0.2453). (3) In the 27 indexes, the volume of highway freight, housing construction area, garden green space area and population density have moderate correlation degrees. The other indexes have strong correlation degrees, among which, the correlation degree of the PM10, O3, total road freight volume and gross industrial output value are relatively high. (4) The synthetic correlation degree values between the PM2.5 pollution sources index layer and PM2.5 are much higher in cities of Nanjing, Wuxi, Changzhou, Nantong and Taizhou. The synthetic correlation degree values between urbanization and industrial structure index layer and PM2.5 are much higher in cities of Xuzhou, Suzhou, Yancheng and Changzhou. The synthetic correlation degree values between the air quality index and meteorological elements layer and PM2.5 are much higher in cities of Yancheng, Yangzhou, Changzhou and Nantong. Our results demonstrate that the grey correlation degrees of the evaluation indexes system are closely related with spatial distribution of PM2.5 in Jiangsu province. Therefore, the grey correlation analysis model can be employed to analyze and evaluate the spatial distribution of PM2.5.
In this paper, according to the intensity of human impacts, a national hierarchical land use intensity classification system was designed based on comprehensive and high-resolution spatial datasets. According to the degree and reversibility of surface disturbance by human activities, we obtained data for four main groups of artificial land, semi-artificial land, semi-natural land and natural land, which were further divided into 22 classes based on indicators such as human population density, and cropping intensity. Land use intensity in China with a 1-km spatial resolution was obtained. The area proportions of artificial land, semi-artificial land, semi-natural land and natural land were 0.71%, 19.36%, 58.93% and 21%, respectively. Besides, significant spatial variability was demonstrated at national, regional and provincial levels. The southeastern region with denser population had more classes of land use intensity and was more intensive than the northwestern region with sparse population. With the increase of longitude, a transition in dominated land use intensity type was detected from natural and semi-natural land to semi-natural and semi-artificial land. The land use intensity in provinces of eastern China was the highest, followed by those in central and western regions. The land use intensity types showed a remarkable spatial differentiation of clustered distribution. Compared with the previous studies, our research effectively characterizes the spatial heterogeneity of land use intensity, which can help us to get a better understanding of spatial pattern of human-environment interactions and its eco-environmental impacts, which can provide scientific basis for sustainable land use policies.
Reconstruction of the historical cropland database could provide an accurate support for the cropland researches on historical periods. Moreover, it will also act as the driving data for the global climate models. In China, there are several ways to rebuild the historical cropland on the regional scale, concerning the traditional cultivation area and the northeastern China. But there are few studies on the national scale, which is primarily due to lacking of accurate historical cropland inventory data. Therefore, it is necessary to simulate the climate and ecosystem scenarios in a wider spatial scale. In the next step, an improvement in the research on reconstruction of the historical cropland database is an efficient and quick method to meet the demand. The present paper has adopted a different approach, which divides the entire landmass of China into cropland area and livestock area according to the climate conditions and cultural diversities of the country. Several representative historical cropland databases are used as the background of our study to ensure the authenticity of the outcomes. Considering the historical land use exploitation, and the impact of the natural and anthropogenic factors on the cropland dynamics, we have developed a partition and layering-based gridded reconstruction method. This is an empirical method for spatial allocation of the historical cropland inventory data in the individual grid cells. Then we use this method to rebuild the historical cropland database maps for China during 1820 (the 25th year in the reign of Emperor Renzong Jiaqing in the Qing Dynasty) and 1936 (the 25th year of the Republic of China), at a resolution of 10 km×10 km. A precision validation is applied on the rebuilt maps by comparing them with other existing regional databases. The results show that this method could ensure the authenticity of the cropland data, with higher accuracy in the regional cropland reconstruction.
The evaluation of land-use/land-cover changes (LUCC) in the arid region was scarcely quantified before the 1980s due to the unavailability of satellite data, resulting in our little knowledge of the effects of LUCC on climate change and carbon/water cycle in that period. In this study, we investigated the evolution of oases in Sangong river basin since the 1950s by using seven land cover maps derived from black-and-white aerial photographs (1958, 1968 and 1978), color-infrared aerial photograph (1987), Landsat TM imagery (1998), SPOT (2004) and Landsat OLI images (2014). Results show that: (1) Since 1950, the new oasis consecutively expanded more than four times towards the bottom of the alluvial plain, causing a huge shrinking of the desert landscapes dominated by haloxylon community and tamarix community. Furthermore, agricultural land had the most rapid expansion during the period of 1958-1968 and built-up areas showed the fastest expansion after the 2000s. (2) Two basic management modes, "local mode" formed by the local governments and "farm management mode" developed by Xinjiang Production and Construction Group, have jointly caused oasis evolution in various LUCC stages. (3) The evolution of modern oasis from the 1950s to 2004 shows the common features of driest oasis area while the period 2004-2014 is characterized by large-scale inter-basin water diversion or some new water sources. (4) The modern oasis expands at the expense of the destruction of desert vegetation, resulting in distinct variation of structure of desert plant community, which will increase the difficulty to protect desert ecosystem.
Taking the semi-arid area of Yulin City as an example, this study improves the vulnerability assessment methods and techniques on the county scale using VSD (Vulnerability Scoping Diagram) assessment framework, integrates the VSD framework and SERV (Spatially Explicit Resilience-Vulnerability) model, and decomposes the system vulnerability into three dimensions including exposure, sensitivity and adaptive capacity. Firstly, with the full understanding of the background and exposure risk source of the research area, the vulnerability indexes were screened out by the SERV model and the index system was constructed to assess the characteristics of the local eco-environment. Secondly, with the aid of RS and GIS, this study measured the spatial differentiation and evolution of social-ecological systems in Yulin City during the period 2000-2011 and explored intrinsic reasons for spatial-temporal evolution of vulnerability. The results are as follows: (1) The spatial pattern of Yulin City's SESs vulnerability is "high in northwest and southeast and low along the Great Wall", although the degree of system vulnerability reduced significantly during the period 2000-2011 and the system development trend is better, there is a sharp distinction in the spatial distribution between the system vulnerability and exposure risk; (2) The evolution of system vulnerability is influenced by the risk factors of exposure, and the regional vulnerability and the spatial heterogeneity of exposure risk are affected by the social sensitivity, economic adaptive capacity and other factors. Finally, according to the uncertainty of decision makers, the future scenarios of regional vulnerability are simulated under different decision risks by taking advantage of the OWA multi-criteria algorithm, and the vulnerability of regional system under different development directions was predicted based on the decision makers' rational risk interval.
Population exposure to high temperature (extremely high temperature) is represented by the multiplication of the population in each grid cell and the projected mean annual number of hot days with daily maximum temperature above 35℃ (40℃) for each corresponding grid cell. Based on daily maximum temperature data from 21 global climate models under the RCP8.5 scenario and population projection data under the A2r socio-economic scenario, population exposures for four future periods (2021-2040, 2041-2060, 2060-2081 and 2081-2100) in China were projected at the grid cell level. The ensemble mean method was used to calculate the annual number of hot days. The relative importance of population and climate as drives of exposures was evaluated at the national level and the meteorological geographical division level. Compared with the population exposure for the 1981-2010 base period, population exposure to high temperature (≥ 35℃) over China for four future periods will increase by 1.3, 2.0, 3.6 and 5.9 times respectively and population exposure to extremely high temperature (≥ 40℃) will increase by 2.0, 8.3, 24.2 and 82.7 times respectively. Population exposure to high temperature will increase significantly in Jianghuai region, Southwest China and Jianghan region, especially in North China, Huanghuai region, South China, Jiangnan region. Population exposure to extremely high temperature will increase significantly in Southwest China and Jianghan region, especially in North China, Huanghuai region, Jiangnan region and Jianghuai region. Climate factors are the most important driver of exposures for Huanghuai region, Jianghuai region, Jianghan region, Jiangnan region, South China and Southwest China, followed by the interact effect of population and climate. At the national level, climate factor is also the most important driver, followed by the interact effect of population and climate. The contribution rate of climate to national-level projected change in exposure will decrease gradually from about 70% to about 60% and the contribution rate of concurrent changes in population and climate will increase gradually from about 20% to about 40% over the four future periods.
Based on objective data collected from interviews in typical villages of the Three Gorges Reservoir area, this study presents three livelihood scenarios related to rural transformation development: agriculturally dominant livelihood, multiple-type livelihood and non-agriculturally dominant livelihood. Results indicated the following: (1) The current farmland pattern shows a trend of diversification as self-cultivation, cropland transfer and fallow in the sample region. Dynamic characteristics of cultivated land present a special feature that is more "transfer-into" than "transfer-out". Various scales of planting are represented among various households, according to the following decreasing order: half-labor household > non-labor household > adequate labor household. (2) The highest pollution loading produced by crop farming occurs in half-labor households while the lowest occurs in non-labor households. With the increase of labor, the pollution load per unit area tends to first increase and then decrease within families with enough labor. (3) As the type of livelihood transitions from agriculturally dominant to non-agriculturally dominant, the maximum reduction of total pollution loading produced by the agricultural industry can reach 72.01%. Compared to agriculturally dominant livelihoods, multiple-type livelihoods produce a pollution load reduction yield of 19.61%-29.85%, and non-agriculturally dominant livelihoods reduce the pollution load yield by 35.20%-72.01%. However, the rate of reduction of total nitrogen is not the same as total phosphorus. (4) The non-agricultural characteristics of labor allocation and income promote the transformation from dominant livelihood types to non-agricultural livelihoods, and potential revenue conversion follows a similar trend. In addition, different household types do not display identical conversion rates, according to the following decreasing order: enough labor household > half-labor household > non-labor household. (5) During rapid urbanization and the building of new industrial systems, the livelihood types of rural households have been further transformed to non-agricultural household types in the mountainous region; this process will lead to the further reduction of pollution load generated by planting and agriculture.
Comprehensive assessment of the positive ecosystem services and disservices provided by urban landscape and evaluation of its contribution of different urban landscapes to total value of ecosystem services, are crucial to optimizing and regulating the urban landscape configuration and the eco-environment construction in rapid urbanization. Based on the knowledge of landscape ecology and ecosystem service and the Landsat images (OLI-TIRS) data, we valued the ecosystem services of urban landscape including its disservices and analyzed their spatial pattern of Xi'an urbanized area by building the models and employing software of ERDAS, ArcGIS10.1 in 2013. The results showed that: (1) The disservice value of urban landscape is remarkably higher than the positive ecological service value, and the net value is approximately -12.71×108 yuan in Xi'an city. In the process of rapid urbanization, the positive service value of urban landscape dramatically decreased and the negative service took up a large proportion of total values resulting from the transformation from natural landscape to semi-artificial landscape and artificial landscape, 87.81% of the urbanized area provided for negative net value of ecosystem services, and only 12.19% of the area provided positive net services. The expansion of urban landscape dominated by large built-up area will inevitably lead to the decline in ecosystem service value. (2) The value of positive ecosystem services provided by urban landscape in Xi'an city varied from urban core area to urban fringe obviously, which is lower in central area than in fringe area; And the high value area close to the road and in the parks shows the mixed patterns with plaque and grid. The total value of negative ecosystem services in the inner area is higher than that in the urban fringe, and high value area is more concentrated in space. Natural landscape and semi-artificial landscape are the main providers of the positive ecosystem services in city. (3) The spatial distribution of the urban landscape fundamentally determines the spatial pattern of the comprehensive ecosystem services, and the mosaic of different urban landscape types reflects the spatial pattern of the positive and negative ecosystem services shaped by the patches and the chessboard structure. The nearer to the area of urban fringe, the higher the comprehensive ecosystem services value is. There are the high value areas where the forest, grassland and water were distributed or scattered in the park or along road side in the city.
Human activities during the early stage in Tibetan Plateau are crucial to improve the knowledge about how human beings react and respond to extreme environmental conditions, especially those in the area with elevation > 4000 m asl, which is considered as the key of the migration and diffusion of human from plain to hinterland. Ash layer dated as 11290±69 cal. a BP and stoneworks such as micro-blade and fine flake mainly occurring at ca.11.2 cal ka BP were found in the archaeological site XDW1, which can be considered as the first evidence to show the human activities above 4000 m asl in the Tibetan Plateau. This study indicates that human beings have migrated to hinterland in the early Holocene, and evaluated the spacial and temporary population diffusion patterns in northeastern Tibetan Plateau: (1) human beings dominated the marginal regions with 3000-4000 m asl in northeastern Tibetan Platean, such as Qinghai Lake Basin and Gonghe Basin during the Last Deglaciation. (2) They expanded to the regions above 4000 m asl during the Early Holocene. (3) People diffused toward hinterland with higher elevation during the Holocene Climatic Optimum. The three stages of human migration and diffusion in the Tibetan Plateau are closely related to the improving climate conditions from the Last Deglaciation until the Holocene Climatic Optimum.
Construction of basin reservoir projects can change the water and sediment transport processes in the lower reaches. The effects of the Three Gorges Project (TGP) on water and sediment transport in lower reaches are emerging. Specifically: (1) The duration and volume of floods in the lower reaches of TGP declined sharply. The sediment value was of such a low concentration that the water was nearly clear. The suspended sediment discharge gradually recovered downwards but its total amount still could not outcompete the annual average of that before the impoundment of TGP. (2) The sediment with d > 0.125 mm recovered to some extent in 2003-2014 (more in 2003-2007 than in 2008-2014) and basically recovered to the average value before the impoundment at the Jianli Station. After recovery, its transport trend in the lower reaches was in line with that before the impoundment. (3) After the impoundment, sediment with d < 0.125 mm recovered to some extent but its total amount was still less than the average of before the impoundment. (4) The recovery of sediment with d > 0.125 mm was mainly from river-bed erosion but with an amount not exceeding 44 million t/y which was primarily limited by duration and average flow of floods and secondarily by the upper mainstream, tributaries between river sections and the sub-sink effects of lakes. Recovery of the suspended sediment with d < 0.125 mm was controlled by the upper mainstream, tributaries between river sections, the sub-sinks of lakes and river-bed compensation. The suspended sediment compensation from river-bed decreased due to the coarsening of bedsands. (4) In 2003-2007 and 2008-2014, both coarse and fine sands were eroded in the Yichang-Zhicheng section in the upper Jingjiang River while coarse sands deposited and fine sands eroded in the lower Jingjiang River. In the Hankou-Datong section, coarse sands deposited and fine sands eroded. From 2003 to 2007, coarse sands deposited while fine sands eroded in the Chenglingji-Hankou section. In 2008-2014, both coarse and fine sands eroded in the Chenglingji-Hankou section. The differences were caused by the duration and volume of the floods in the Luoshan Station.
Supported by the National Natural Science Foundation of China, research on geomorphology has made great progress in China. Based on its funding information for projects on geomorphology from 2010 to 2015, a summary of the overall development on the funded projects of geomorphology was made and the regional imbalance in the geomorphological branches was also analyzed. Consequently, some hotspots, as well as the research achievement and effect, were summed up. In this paper several major results can be drawn as follows. Firstly, the mumber of funded projects has showed an upward trend, which indicates that the relevant research is gradually deepening, and research teams have been expanding steadily. Secondly, research institutions on geomorphology are diversified from dual structure to multivariate one. Thirdly, geomorphology among different fields has shown a regional imbalance in terms of research subject and hot issues. Fourthly, tectonic landform, fluvial landform, loess landform, glacial landform and aeolian landform have become the main research hotspots of geomorphology.
Based on Journal Citation Reports, Web of Science, Springer data and manuscripts statistics data, we analyzed the citation indices of Journal of Geographical Sciences (JGS) from 2011 to 2015. The main indices include the number and rate of internaltional manuscripts, published articles, downloads, impact factors, total cites, cited journals, citing journals, highly cited papers. The internaltional manuscripts come from more countries. Up to 2015, JGS has received manuscripts from 80 countries and published papers from 32 countries. The citation indices of JGS show increasing trends in recent 5 years. Impact factor of JGS increased from 0.832 in 2011 to 1.923 in 2015. Total cites increased from 366 in 2011 to 1276 in 2015. The international download number of papers in JGS increased year by year, and the download number in 2015 was 2.82 times that of 2011. The published papers have good influences. The research can provide scientific suggestions for the development of Journal of Geographical Sciences and references for the quality improvement of other Chinese geographical journals.
