Geography is a subject to explore spatial distribution, time evolution and regional characteristics of geographical elements or geographical complexes. Geography is unique in bridging social sciences and natural sciences, and has characteristics of comprehensiveness, interdisciplinary research and regionalism. With the development of geographical science technology and research methods, geography is in the gorgeous historical process towards geographical science. Research themes of geography are focusing on the comprehensive research on the earth surface. The research paradigms of geography are shifting from geography knowledge description, coupling pattern and process, to the simulation and prediction of complex human and earth system. The development of Chinese geography needs to be rooted in the major needs of national strategy, and plays important roles in the studies of urbanization development, coupling ecological processes and services, water resources management and geopolitics. Under the country's major needs, China's geography tends to achieve the geography theory innovation, new method and technology application and developed disciplinary system with Chinese characteristics, and make more contribution to national and global sustainable development.
Geography focuses on the interaction among factors on earth surface, and their spatial distribution and temporal evolution. Human environment interaction constitutes the core of this discipline. Geography is also by and large based on regional studies. As an academic discipline, it has not only substantially contributed to national sustainable development and ecological progress, but also enabled us to better understand and deal with issues with regard to resources, environment, and urbanization emerging in the last few decades alongside economic development. Geography at Peking University always seeks to move beyond the current academic frontier on the one hand, and to meet the national strategic needs on the other. It now has two national key secondary disciplines, physical and human geography, and one primary discipline, ecology.
The development of integrated physical geography at Peking University can be traced back to 1952, when the national department adjustment was taken and the Department of Physical Geography was set up at Peking University. Over the course of more than half a century, a discipline system of integrated physical geography has been gradually formed facing the disciplinary frontier and national needs. In view of the increasingly severe problems related with climate change, natural resources, eco-environment and socio-economic development, integrated physical geography of Peking University has made great progress in land surface process and mechanism, land use/cover change and its eco-environmental effects, ecosystem services and human well-beings, ecological risk assessment and security pattern construction, and physical geographical division, taking a leading role in the development of China's integrated physical geography. Looking forward to the future, the integrated physical geography of Peking University will continue to focus on the mechanism of pattern and process of water, soil, climate and biology, the effects of human activities and global environmental changes on natural geographical process and pattern, quantitative assessment of factors and processes coupled with the regional resources and eco-environmental effects and associated socio-economic impact, constructing a fusion system through coupling observation data and land surface model, so as to make contributions to national strategy such as construction of ecological civilization, main function-oriented zoning, territorial development, and integrated watershed management.
The Human Geography Discipline at Peking University (PKU) originated from the Economic Geography Discipline at the Geology and Geography Department which was established in 1955. The department is the first comprehensive teaching and research institute which has teaching, research, and practice activities in the Human Geography Discipline in China. Over the past 60 years, the Human Geography Discipline at PKU has been emphasizing the importance of both teaching and research, and giving priority to practice over theory. It has been experiencing a shift from focusing on the basic theory of the Human Geography Discipline to integrating both basic and applied research. Both an interdisciplinary way of research thinking and an interdisciplinary subject of human geography have been formed with a coordination between liberal arts, sciences and engineering. The Human Geography Discipline is operated together by the Department of Urban and Economic Geography, the Department of Urban and Regional Planning, and the Research Institute of Historical Geography. In the past 60 years, the Human Geography Discipline at PKU has achieved a series of well-recognized, innovative and high impact research outputs in both domestic and overseas in the fields of urbanization, urban system, urban and regional planning, land use assessment and planning, industrial location and regional industry evolvement, industrial clusters and innovation network, housing and real estate economy, scenic areas and world heritage, village and township development planning, urban social geography, time geography and behavior geography, historical geography, tourism geography research and planning, quantitative geography, transport geography and transport planning. These research outputs provide important scientific and technological supports to the national social and economic development, and have significant contributions to sustainable development of the society, the economic system and the urban-rural areas. In the future, the Human Geography Discipline at PKU will be engaged in servicing the national strategies and commit itself to pioneer the discipline development. It will continue to grow with a stress on communications and collaborations between disciplinary subjects. It will enhance its capability to serve the decision making for national strategy, and increase its reputation and influences in the field of human geography research in the world.
As a result of the reorganization of the universities and academic departments in 1952, Peking University set up the Department of Geology and Geography and started the teaching and research in Geomorphology and Quaternary science. This marked the establishment of the discipline of Geomorphology and Quaternary at Peking University. Over the past 65 years, great achievements have been made in the fields such as neotectonic activity and tectonic geomorphology, climatic geomorphology, fluvial geomorphology and sedimentology, sedimentary facies and comparative sedimentology, remote sensing and geographical information system, Quaternary stratigraphy and chronology, Quaternary climate and environmental change, marine geochemical processes and environmental evolution, and environmental archaeology and past human-environment interaction. These progresses have not only played an innovative and leading role in some of the related research areas, but also helped to solve a series of practical problems in the national economic development, thus representing great contribution to the development of Geomorphology and Quaternary science in China.
With the increasing diversification in the field of geography, the discipline development and scientific research of Geomorphology and Quaternary Science in Peking University will strengthen integration with all branches of physical geography and other fields of Earth Science within the framework of Earth System Science. To contribute more to the development of Geomorphology and Quaternary Science in China, particular emphasis will be put on the research on the links between the geomorphological evolution of different macroscopic spatio-temporal scales and the modern processes, and on the understanding of complex impacts of various components of the earth system on the evolution of geomorphology. Systematic simulation and numerical modeling on the climate change, environmental evolution and geomorphologic processes will be developed. Both theoretical research and the development and application of new technology in Geomorphology and Quaternary Science will be strengthened.
The biogeography research at Peking University commenced in the late 1950s with formation of a Plant Geography Group. It was expanded to the Teaching and Research Section of Landscape Ecology in the late 1980s and further grown into the Department of Ecology at the beginning of the 21st century. As a part of the Department of Geography (Now College of Urban and Environmental Sciences, Peking University), biogeographical and ecological research team of Peking University has greatly improved the research of vegetation structure, function and dynamics with efforts of more than half a century. It has made pioneering achievements on research about plant geography in arid and semiarid areas, timberline and other ecologically important areas. It is among the first institutions in the country to promote macro-ecology including landscape ecology and urban ecology. In recent years, the Peking University research team has carried out pioneering work on global change studies, including climate change and ecological response, carbon cycle, biodiversity conservation, plant stoichiometry, serving the country's policy of mitigating and adapting climate change and conserving biodiversity. Research facilities of Peking University biogeography and ecology team have renewed and built over the last years. The construction of observation facilities in Saihanba Ecological Station, the platforms of forest fertilization experiment, and timberline monitoring strongly enhance the ability of biogeographical and ecological studies. The National Natural Science Foundation Innovation Research Team "Structure and function of terrestrial vegetation in China" has played a role of research integration. In the future, the integration of different scales of ecological research will be strengthened and ecological degradation and restoration will be promoted.
The environmental geography research at Peking University has been conducted in the College of Urban and Environmental Sciences, with the support of Ministry of Education Laboratory for Earth Surface Processes Analysis and Simulation. They grew out of the Environmental Research Section of Physical Geographical Specialty of the Department of Geography at Peking University. In 65 years of geographical research at Peking University, environmental geography research was initiated from traditional physical geography, and developed into chemical geography and environmental geography gradually in the 1970s, due to the emerging environmental pollution and ecological degradation issues in this period. Since then, the research areas have been widened gradually. Nowadays, relying on the discipline of environmental geography, one of the branches of geography, researchers in the Department of Environment Sciences have made creative achievements in the fields such as regional environmental processes of toxic pollutants, biogeochemical cycling and interface migration of pollutants, toxicological effects of pollutants and their ecological and health risks. Now, their research holds a leading position in China. In addition, this department carried out a number of applied studies and consulting studies on environmental hotspots of China, such as environmental policy making, environmental and resource law drafting, and contaminated land remediation. Their studies have played significant roles in environmental protection, ecological conservation and sustainable development of the country. In the last decades, we have fostered many high-level professional talents, who have made remarkable achievements after their graduation. In the future, the environmental geography research team at Peking University will continue its efforts in scientific research and personnel training, especially in providing comprehensive solutions for regional environmental governance, as well as for some key environmental problems related to air pollution and soil pollution, so as to meet the needs of the country.
IImpervious surface (IS) is often recognized as the indicator of regional ecosystems and environmental changes. Its spatio-temporal dynamics and ecological effects have been studied by many researchers, especially for the IS in Beijing municipality. However, most previous relevant studies examined Beijing as a whole without considering the differences and heterogeneity among the functional zones. In this study, the urban expansion in Beijing in some typical years (1991, 2001, 2005, 2011 and 2015) was analyzed by sub-pixel IS that obtained through the simulation of CART and change detection models. Then the spatio-temporal dynamics and variations of IS (1991, 2001, 2011 and 2015) in different functional zones and counties were analyzed based on the method of standard deviation ellipse, Lorenz curve, contribution index (CI) and landscape theory. It is found that the total area of impervious surface in Beijing increased dramatically from 1991 to 2015, increasing about 144.18%. The deflection angle of major axis of standard deviation ellipse decreased from 47.15° to 38.82°, indicating a trend that the major development axis in Beijing moved from the northeast-southwest orientation to the north-south orientation. Moreover, the heterogeneity of IS distribution in different counties weakened gradually but the CI values and landscapes in different zones differed greatly. Urban function extended zone (UFEZ) had the highest CI value, which means it played the most important role in the growth of IS in Beijing, and its lowest CI value was 1.79 during the study period, which is much greater than the highest CI values of other functional zones. Core functional zone (CFZ) contributed less than UFEZ, but it has the highest CONTAG value, showing a more connected IS landscape compared with other zones. The CI values of new urban developed zone (NUDZ) increased rapidly from 1991 to 2015, which increased from negative to positive and multiplied, indicating the NUDZ has become the main source for the growth of IS in Beijing gradually. However, the ecological conservation zone made a negative contribution at all times, and its CI value decreased constantly. In addition, the variations of landscape indices and centroids of impervious surface in different density classes indicate that the high-density impervious surface had a more compact configuration and a greater impact on the ecological environment.
Coastal prograding tidal flats are important wetlands and reserve resources of cropland in China, which provide the services of ecological protection, society security, and economic development. Taking the reclamation zones on the prograding coast of Jiangsu as a case study, this paper analyzed soil quality at the reclamation zones with a duration of 0-40 years to indicate the evolution of cropland quality following reclamation for sustainable use of cropland, by using the method of "space for time substitution". The results show that cropland soils had high salinity but low nutrients. The variation of soil physical and chemical properties is high in the coastal reclamation zones, and the soil particle sizes had obvious gradients of North-South and Land-Sea. The factors such as topography, vegetation status, and the path of tidal flats to cropland had significant impacts on cropland quality evolution following coastal reclamation. The path of tidal flats to cropland were jointly decided by physical condition of reclamation zones, development entity, and development scale in the coastal area of Jiangsu. The cropland trajectories have changed from "halophytes→aquaculture pond→cropland" to "halophytes→cropland" in the central part of the province's coastal area. This change shortened the period of tidal flats to cropland, but led to idle tidal flats after reclamation. The soils of coastal tidal flats have gradually transferred into soils of cropland. The changing trends of soil properties were divided into four types. The first one was the type of increase, such as soil total phosphorous, available phosphorous, and clay content. The second one was the type of decrease, such as sand content. The third one was the type of increase then decrease, such as soil salinity and pH. The fourth one was the type of decrease then increase, such as soil organic matter, total nitrogen, available nitrogen, and capacity of exchange cations. At the initial period of reclamation, soil organic matter showed a declining trend because of the process of mineralization. The soil salinity and pH increased due to transpiration and evaporation. At the middle period of reclamation, soil organic matter and nutrients increased because of the fertilization and organic matter input via human cultivation. Soil salinity and pH decreased as a result of precipitation and water resource facilities. At the later period of reclamation, the factors of soil quality fluctuated under the effect of cultivation management. The quality of cropland at the reclamation zones was fragile and sensible to cultivation management, because of the relatively short history of coastal reclamation.
Nowadays, the urban agglomerations in the eastern coastal area of China have been the strategic core regions of national economic development and part of the main regions of the new-type urbanization. However, they suffer a series of eco-environment problems, such as increased consumption of resources, energy and materials. Thus, over the past few years, the eco-environment problem of urban agglomerations has become the forefront subject in the field of geographical research. The paper is unfolded with the definition of the eco-efficiency of urban agglomeration, which is taken as the measurement index of sustainability of urban agglomerations. Subsequently, with the aid of the traditional DEA model and undesirable output model of SBM, the paper carries out a comparative evaluation of the economic efficiency and ecological efficiency of the four major urban agglomerations in eastern China in the three periods of 2005, 2011 and 2014, and analyzes the spatio-temporal characteristics of evolution of urban agglomerations. In conclusion, with an analysis of laxity, the paper proposes corresponding suggestions for the improvement of eco-efficiency of the four major urban agglomerations in coastal China. As is suggested in the results, first and foremost, the overall economic efficiency of urban agglomerations located in Shandong Peninsula, Yangtze River Delta and Pearl River Delta displays a V-shaped pattern of "first decrease and then increase". In contrast, the overall economic efficiency of the Beijing-Tianjin-Hebei urban agglomeration declines from the beginning to the end. Before 2011, a significant impact of pure technical efficiency is displayed, and after 2011, it is greatly affected by scale efficiency. Secondly, the Beijing-Tianjin-Hebei urban agglomeration suffers from a considerable loss of efficiency due to the impact of pollution. In contrast, there is a less severe loss in the efficiency of Shandong Peninsula urban agglomeration. On the whole, the eco-environment efficiency of the four major urban agglomerations was at a descending stage from 2005 to 2011, and at a revival stage from 2011 to 2014. In addition, the spatio-temporal pattern of urban eco-efficiency in the four major urban agglomerations in the coastal areas is possessed with different evolution characteristics. The peri-urban areas of core cities and riverside and seaside areas have a better urban eco-efficiency, and the inland cities have an inferior urban eco-efficiency. Apart from that, it is found that the core cities of the Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta urban agglomerations have a high resource consumption, economic benefit output and high eco-efficiency. Overall, most cities in the urban agglomerations demonstrate a declining tendency of pollution emissions, together with marked reduction of pollutants and mitigation of environmental problems. Last but not least, the economic eco-efficiency of the four major urban agglomerations is influenced by different factors. The paper conducts a differential analysis from the perspective of urban agglomeration, and proposed the concrete suggestions.
The research on the interactions among multiple ecosystem services (ES) is a hotspot. Most of the previous studies focused on the qualitative description of ES interactions, however, there have been relatively few studies on spatially explicit and quantitative assessment of ES interactions. In this paper, we mapped the ecosystem service of soil conservation (SC), net primary production (NPP) and water yield (WY) in the upper reaches of Hanjiang River Basin (URHR) based on the land use and land cover (LULC), NDVI, soil properties and observed climate data covering 2000-2013. Moreover, we quantitatively assessed the variation characteristics of interactions among different ES with a spatio-temporal statistical framework by applying the partial correlation analysis at a pixel scale. The results are shown as follows: (1) From 2000 to 2013, the mean annual SC was 434.20 t·hm-2·yr-1, and the mean annual WY was 250.34 mm. They also presented a rising tendency at the rate of 16.10 t·hm-2·yr-1 and 3.79 mm·yr-1, respectively. However, the mean annual NPP was 854.11 gC·m-2·yr-1, and presented a decreasing tendency at the rate of 8.54 gC·m-2·yr-1. (2) Spatially, SC was high in the North-South mountain area, while it was low in the Middle valley region. Similarly, the NPP in the Middle valley region was lower than that of other regions. However, the WY increased from north to south. (3) The three pairwise ES presented different interactions. Both the interaction between SC and NPP and that between SC and WY presented as trade-off, accounting for 62.77% and 71.60% of the total area, respectively. On the contrary, the interaction between NPP and WY was prone to synergies, accounting for 62.89% of the total area. (4) Pairwise ES in different land cover types also presented a different interaction. As for woodland, wetland, cropland, artificial land and bare land, SC and NPP, as well as SC and WY both presented trade-off, while WY and NPP presented synergy. Specially, in grassland, all the three pairwise ES presented a trade-off relationship. Therefore, spatially explicit and quantitative assessment of ES interactions are more helpful for revealing the temporal non-linear evolution, and the spatial heterogeneity of ES interactions. This analysis framework also contributes to the regional sustainable land management and the optimization of multiple ES conservation.
High concentration of PM2.5 has been universally considered as a main cause for haze formation. Therefore, it is important to identify the spatial heterogeneity and influencing factors of PM2.5 concentration for the purpose of regional air quality control and management. Using PM2.5 data from 2000 to 2011 that is inversed from NASA atmospheric remote sensing images, and employing the methods in geo-statistics, geographic detectors and geo-spatial analysis, this paper reveals the spatio-temporal evolution patterns and driving factors of PM2.5 concentration in China. The main findings are as follows: (1) In general, the average concentration of PM2.5 in China has increased quickly and reached its peak value in the year of 2006; after that, it has been maintained at around 22.47-28.26 μg/m3. (2) PM2.5 is strikingly uneven in China, with a higher concentration in North and East than in South and West, respectively. In particular, the areas with a relatively high concentration of PM2.5 are mainly the four regions including the Huang-Huai-Hai Plain, the Lower Yangtze River Delta Plain, the Sichuan Basin, and the Taklimakan Desert. Among them, Beijing-Tianjin-Hebei Region has the highest concentration of PM2.5. (3) The center of gravity of PM2.5 has shown an overall eastward movement trend, which indicates an increasingly serious haze in eastern China. Particularly, the center of gravity of high-value PM2.5 is kept on moving eastward, while that of the low-value PM2.5 moves westward. (4) The spatial autocorrelation analysis indicates a significantly positive spatial correlation. The "High-High" PM2.5 agglomeration areas include the Huang-Huai-Hai Plain, Fenhe-Weihe River Basin, Sichuan Basin, and Jianghan plain regions. The "Low-Low" PM2.5 agglomeration areas include Inner Mongolia and Heilongjiang to the north of the Great Wall, Qinghai-Tibet Plateau, and Taiwan, Hainan and Fujian and other southeast coastal and island areas. (5) Geographic detection analysis indicates that both natural and human factors account for the spatial variations of PM2.5 concentration. In particular, factors such as natural geographical location, population density, automobile quantity, industrial discharge and straw burning are the main driving forces of PM2.5 concentration in China.
This article takes remote sensing as one of measurements. The paper overviews the general methodology from remote sensing observations to data products, and categorizes the existing methods into two types: target recognition and parameter retrieval together with their features, advantages and shortcomings. Even after 50 years of continuous research, we are still lack of consistent and scientific methodology to produce data products from remote sensing observations. In the future, in order to build up scientific and structured remote sensing methods for data products, the priority should be given to further development of multi-angle, multi-temporal, multi-spectral, and multi-source as well as both active and passive remote sensing observations, so as to develop new remote sensing indices, which have obvious ecological, geographic, agronomic meanings, to promote the normalization and standardization of remote sensing methods, and to generate synthetic products based on all available remote sensing observations instead of single remote sensing observations. Big data and cloud computing will provide support for the process from remote sensing observations to data products.
