EN中文

Archive

  • Select all
    |
    Feature Paper
  • Feature Paper
    Open GIS for big data：opportunities and impediments
    Dianzhi SUI, Xinyue YE, Tian GAN
    2014, 33(6): 723-737. https://doi.org/10.11820/dlkxjz.2014.06.001
    Download PDF ( )   Knowledge map   Save
    The field of Open GIS(S for Systems, Sciences, Services, and Studies) is at a cross-road in the early 2010s. Aiming to link the multiple visions for the next phase of GIS development, this paper suggests that the emerging Open GIS should serve as a guiding concept. Contextualized in the broader literature of open science, this paper proposes Open GIS should include eight dimensions related to data, software, hardware, standards, research, publication, funding, and education. For the GIS community, Open GIS offers four exciting opportunities: a) technology-driven opportunities for addressing challenges posed by the (spatial) big data deluge; b) application-led opportunities for improving individual and collective decisions; c) curiosity-inspired, crowd-powered opportunities for the development of an open and geographic citizen science for understanding the changing planet; d) education-focused opportunities for implementing the vision of a spatial university. Although there are academic, legal, social/political, and environmental impediments for the practice of Open GIS, Open GIS will become increasingly important in shaping our research and educational agendas in the future.
    • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
  • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
    Modeling China’s geopolitical influence in surrounding areas：a case study of South Asia
    Wang Shufang, GE Yuejing, CAO Yuan, HU Hao
    2014, 33(6): 738-747. https://doi.org/10.11820/dlkxjz.2014.06.002
    Download PDF ( )   Knowledge map   Save
    Current international society has entered an era of large-scale power transfer, and power tends to become more flexible and intangible. The proposed concept of geopolitical influence (geo-influence) conforms to this trend of power structure change in international relations, providing a new perspective for analyzing national comprehensive strength. Geo-influence includes hard power, soft power and interdependent power, which is an overall reflection of state external communication and coordination capacity. It can be an important index to measure national strength. This paper attempts to develop a method for measuring countries' national geo-influence. It defines the concept of geo-influence based on power theory, hard power and soft power theory and interdependence theory. Highlighting the dominant factors and the operational principles, the paper constructs an evaluation system and mathematical model of national geo-influence, estimates the comparative strength of China and South Asian countries in 2012, and calculates China's geo-influence values in different South Asian countries and the overall South Asian region over the past decade. The results show that: (1) The ranking of comprehensive strength ratio of China and South Asian countries in 2012 is India, Pakistan, Bangladesh, Sri Lanka, Nepal, Bhutan and Maldives in ascending order. In South Asian countries, the gap in comprehensive strength between China and India is the smallest, while the gap between China and Maldives are the largest. It indicates that geopolitical significance of a state, especially hard power is still an important support of comprehensive strength. (2) China's geo-influence in South Asia has shown an increasing trend, indicating that China's overall influence has been rising gradually in this region over the past decade. Among these countries, China's geo-influence value is high in Bhutan, Bangladesh and Nepal, but relatively low in Sri Lanka and Maldives. This demonstrates that geoinfluence is restricted by location and distance, with a spatially attenuating tendency. (3) Comprehensive strength is not proportional or positively correlated to a country's geo-influence. The gap in comprehensive strength between China and India is the smallest, but China's geo-influence in India lies in the middle range. On the other hand, the gap of comprehensive strength between China and Maldives is the greatest, but China's geoinfluence in Maldives is the lowest. (4) The gap in soft power between China and South Asian countries is small in terms of policy and institutional arrangements, national image and cultural exchanges. On the whole, the China's cultural influence in South Asia is weak, but it has been increasing slowly over the past decade.
  • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
    Population size, distribution and factors impacting on citizenization of Chinese migrant workers
    LIU Rui, CAO Guangzhong
    2014, 33(6): 748-755. https://doi.org/10.11820/dlkxjz.2014.06.003
    Download PDF ( )   Knowledge map   Save
    China's urbanization rate increased from 18% in 1978 to 52.57% in 2012, but the citizenization rate as indicated by the urban population registration (hukou) is only 27%. The gap between urbanization rate and citizenization rate is accounted for by the rural-urban migrants who live and work in cities without the social welfare provided by the city governments. Promoting the citizenization of rural-urban migrants is a long-term and arduous task. To some extent it will decide whether China's urbanization can proceed smoothly and sustainably. This paper studies rural-urban migrants who need to be citizenized. Some existing research has provided estimates on the total size and annual increase of rural-urban migrants who need to be citizenized nationwide. However, these studies generally contain no data on the population size at the provincial level and the geography distribution of such population. This paper tries to fill this gap. Based on the data from the Sixth Census in 2010 and the county-level population statistics published by the Ministry of Public Security yearly, we estimate the migrants' population size of each province and the proportion of migrants with urban hukou among total migrants (short for MhM). The result indicates a clear difficulty for rural-urban migrants to get an urban hukou. Firstly, the annual increase of migrants who need to be citizenized is 15.76 million nationwide. The coastal areas have the highest annual increase in the size of migrant population. Inland areas take the second place. Coastal areas mainly receive inter-provincial migrants. The proportion of inter-provincial migrants is more than 70% in coastal areas such as Guangdong, Shanghai and Zhejiang as well as Beijing. In inland areas migrants mainly move within the same province. The proportion of inter-provincial migrants is less than 10%. Secondly, nationwide the MhM is 40.85%, which means more than half of the migrants did not have an urban hukou in the cities they work. The migrants in inland areas can get the city hukou with the least effort. In Henan, Guizhou and Chongqing the MhM is higher than 70%. The most difficult area to receive an urban hukou locates in the coastal area of southeast China. The MhM of Shanghai, Zhejiang, Guangdong and Beijing are less than 30%. Inter-provincial migrants get urban hukou more easily than intra-provincial migrants. The MhM of inter-provincial migrants is 2 percentage points higher than intra-provincial migrants. Thirdly, with correlation analysis of 10 influencing factors and the MhM, we found that high cost of citizenization, especially the huge public spending required for providing social welfare for migrants; the unreasonable budget-sharing mechanism; and the rigid restrictions of the current policy on settling in cities are the main obstacles for migrants to receive urban hokou and social welfare. Based on these conclusions, some suggestions about the citizenization of rural-urban migrants are put forward. The current social security financing mechanism should be reformed to increase the proportion of financial expenditures of the central government. Meanwhile, the central government should make different settlement policies based on the migration characteristics and urbanization processes in different provinces. The inland areas should relax restrictions on settlement and allow more migrants to receive urban hukou. The coastal areas should link the financial subsidies with migrants' residence permits instead of hukou.
  • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
    Neighborhood influences on adolescent development under the background of urban residential space differentiation：a case study of Lujiang Village and Yijing Community
    SUN Yukang, YUAN Yuan
    2014, 33(6): 756-764. https://doi.org/10.11820/dlkxjz.2014.06.004
    Download PDF ( )   Knowledge map   Save
    In recent years, with the rapid urbanization and economic and social transitions, social class stratification began to emerge in China, and residential space differentiation in Chinese cities has become increasingly apparent. Chinese scholars have started to examine the residential space differentiation phenomenon and its effects. Using survey data and in-depth interviews, this research explores the effects of neighborhood characteristics on adolescent education and development, taking Lujiang Village and Yijing Community in the haizhu district of Guangzhou as cases. Neighborhood characteristics include its socioeconomic, institutional resource, education concept, and peer interaction characteristics. The development results of teenagers include aspects such as learning ability, psychological states, personality and future development opportunities. Based on the selected variables, this paper uses a logistic regression model to analyze the relationship between the variables. At first, the research preliminarily determines whether the independent variables affect the dependent variable according to the results of model analysis. It then uses data from the questionnaire survey and interviews in the two communities to confirm whether the results of model analysis are consistent with the actual situation. This study shows that these four aspects do have various degrees of effects on adolescent education and development. Firstly, neighborhood socioeconomic characteristics affect the adolescents' learning ability. Parents who live in a highly educated, affluent and prestigous neighborhood have more experience and can spend more time and money on their children's education. Secondly, the education concepts and behavioral characteristics of families affect the adolescents' psychological states. More communication between parents and children and emphasis on the children's education make the relationship between the children and their parents more harmonious and reduce stresses of children. By comparing similar poorly educated families in two different communities, this research found that the poorly educated families living in the upscale neighborhood are obviously affected by the highly educated families—they share similar education concepts and adopt similar behaviors, and their children have similar development results. The same is true for the poor neighborhood, Lujiang Village. Thirdly, peer interaction characteristics affect adolescents' personality. Teenagers living in poor communities face more intense relationships and are more marginalized and they are more easily bullied by other teenagers, leading to their introverted character and more negative emotions. Lastly, institutional resource characteristics affect the adolescents' development opportunities. High quality of teaching, good facilities and rich campus activities increase the probability of students to enter key middle schools. The mechanism of neighborhood effects can be explained by the neighborhood institutional resource model and the collective socialization model put forward by Jencks and Mayer. In the institutional neighborhood resource model, neighborhoods affect the development opportunities of adolescents by providing different qualities of public services such as schools and sports facility. In the collective socialization model, neighborhoods influence adolescents' values, personality and behaviors and habits by affecting families' concepts and behavioral characteristics and interpersonal relationships between peers.
  • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
    Impact of rail transit on the residential property prices of submarkets：a case of the Longgang Line of Shenzhen
    WANG Fuliang, FENG Changchun, GAN Lin
    2014, 33(6): 765-772. https://doi.org/10.11820/dlkxjz.2014.06.005
    Download PDF ( )   Knowledge map   Save
    Studying the impact of rail transit on residential property prices along rail lines will facilitate the internalization of external benefits of rail traffic. It has significant importance for the construction and operation of city subways. In real urban space, because of the presence of spatial heterogeneity the impact of rail transport is not always the same in different areas, thus it requires the examination of submarkets. This research takes the suburb segment of the Longgang Line in Shenzhen as a case. Firstly, Moran'I index is used to confirm the effect of spatial autocorrelation. Then a variable representing spatial autocorrelation are constructed to be included in the model. In total four models are constructed. Chow Statistics is then adopted to divide the submarkets into suburbs near central city and suburbs at the city periphery. After that, the Hedonic pricing model is selected to study the submarket impact of the rail transit on housing prices along the rail line. The results show that: (1) rail transit has a positive impact on housing prices along the rail line in the close to central city segment. (2) Concerning the impact of rail transit on housing prices, submarket effect does exist. In different submarkets, the impacts of rail transit on housing prices vary, sometimes are even in opposite directions. In the close to urban center segment, rail transit has a positive impact on housing prices. In the remote suburban segment, rail transit has a negative impact on housing prices. (3) Submarkets can be divided by Chow Statistics test. The dividing point of the Longgang Line is Liuyue-Danzhutou. The spatial extent of the close to center suburban submarket may be related to the city's average commuting time. (4) The cause of submarket division is spatial heterogeneity. The submarkets of the Longgang Line suburban segment is determined by the spatial differences between the two regional centers.
  • PrizeWinning Papers from the 8th Graduate Students' Geographical Forum of Beijing
    Spatial temporal characteristics of development efficiencies for urban tourism：a case study of three urban agglomerations in the Bohai Rim
    LI Rui, GUO Qian, HE Ji, WU Dianting, YIN Hongmei, YE Qian
    2014, 33(6): 773-785. https://doi.org/10.11820/dlkxjz.2014.06.006
    Download PDF ( )   Knowledge map   Save
    Taking prefecture-level cities, provincial cities and provincial capitals of three urban agglomerations in the Bohai Rim as analytical units, this paper measures and analyzes urban tourism development efficiency and spatial characteristics and development stages of these urban agglomerations by adopting the traditional DEA and Malmquist models. Major conclusions include: (1) The average comprehensive resource utilization efficiencies of urban tourism of municipalities, provincial capitals and main prefecture-level cities of the Beijing-Tianjin-Hebei and Shandong Peninsula urban agglomerations have transformed from ineffective to moderately effective, and those of Eastern Liaoning Peninsula urban agglomerations have been always ineffective. The comprehensive resource utilization efficiencies of prefecture-level cities, provincial cities and provincial capitals of the three urban agglomerations have transformed from ineffective to moderately effective. (2) Since 2000, the comprehensive efficiencies of urban tourism of the Beijing-Tianjin-Hebei and Shandong Peninsula urban agglomerations have been affected by pure technical efficiency slightly more than scale efficiency, while it is the opposite for Eastern Liaoning Peninsula urban agglomerations. (3) The Total Factor Productivity (TFP) of most cities in the three urban agglomerations has substantially increased since 2000; the TFP increasing rates of the Beijing-Tianjin-Hebei and Shandong Peninsula urban agglomerations are both slightly higher than those of Eastern Liaoning Peninsula urban agglomerations; however, the overall rates of increase of TFP have declined. Meanwhile, the average TFP increasing rates of urban tourism of the Beijing-Tianjin-Hebei and Shandong Peninsula and Eastern Liaoning Peninsula urban agglomerations also have declined. (4) The development efficiencies of urban tourism of the Beijing-Tianjin-Hebei urban agglomerations have been affected by urban tourism investment, urban tourism technology and urban tourism markets; those of Shandong Peninsula urban agglomerations have been affected by urban tourism products and urban tourism technology; development efficiencies of urban tourism of Eastern Liaoning Peninsula urban agglomerations have been affected by urban tourism resources, urban tourism policies and urban tourism projects (products). The comprehensive efficiency of urban tourism of the three urban agglomerations has been in the technology innovation stage, the technology imitation stage and the scale dominance stage, respectively. These conclusions provide a theoretical basis for the scientific development of urban tourism of the three urban agglomerations in the Bohai Rim and other coastal urban agglomerations in China.
    • Quaternary Research
  • Quaternary Research
    Holocene humidity changes in inland China inferred from lake sediments
    GUO Chao, MAYuzhen, HU Caili, WU Yongqiu, LU Ruijie
    2014, 33(6): 786-798. https://doi.org/10.11820/dlkxjz.2014.06.007
    Download PDF ( )   Knowledge map   Save
    Environmental changes recorded by lake sediments have been one of the major tools for reconstructing the palaeoenvironment and palaeoclimate in many parts of the world. Spatial and temporal patterns of humidity changes during Holocene have been reconstructed based on the compilation of recently published paleoclimate records from the inland areas of China. The climate of this region is sensitive to large-scale climate forcing. We divided China's inland areas into the arid northwestern region, the East Asian monsoon-margin region and the Qinghai-Tibet Plateau according to the amount of precipitation and natural zones. Sediment records from 30 lakes with reliable chronologies and robust proxies were selected to reconstruct dry-wet conditions based on a three-class ordinal wetness index (dry, sub-humid, humid) with assigned scores from dry to wet periods at individual sites for 500-year time slices. Then we formulated the regional dry-wet index, which may represent the average change of the regional dry-wet conditions. The proxies used in these records include pollen assemblages, oxygen isotope ratio (δ18O), organic matter and carbonate content (mainly pollen assemblages) data. The results of our synthesis show that the moisture conditions have experienced diverse changes over the Holocene in different regions of china's inland areas. Arid climate prevailed during the early Holocene, and relatively wet climate characterized the middle and late Holocene in arid northwestern China. But the climate change differed from place to place—the further into the west, the drier the climate during the early and middle Holocene and wetter in the late Holocene. In the East Asian monsoon-margin region, drier climate also prevailed during the early Holocene, and a wetter period may had occurred in the mid-Holocene, then the climate underwent another transition—it was driest in the late Holocene. In the Qinghai-Tibet Plateau, the wettest period may had occurred in the early and mid-Holocene, then the climate became dry gradually, but there was a tendency of wetness in late Holocene. The wet periods in eastern Qinghai-Tibet Plateau were longer than in the central and western regions. The comparative analysis reveals that the climate may have been mainly controlled by westerly circulation in arid northwestern China. But there were differences among the lake records in the timing of the beginning and end of the dry or humid periods as well as the intensity of the dry or wet conditions, which may be related to the strength of the Asian monsoon in the early Holocene and the influence of westerly circulation in the late Holocene. Furthermore, the insolation, global ice-sheets and topography of the Tibetan Plateau may have played important roles in controlling climate change in this area. The climate change in the East Asian monsoonmargin region is mainly influenced by the East Asian monsoon, which has also been recorded by the loess and desert deposits. The moisture conditions in the Qinghai-Tibet Plateau may have been controlled by the Indian monsoon, and the wetness in the early Holocene may be related to the strengthening of the Indian monsoon. Around 4 ka BP, a significant dry event commonly occurred in China's inland areas, which may be a global dry event that may have resulted in the decline of some ancient civilizations in the whole world.
  • Quaternary Research
    Spatial variation of palaeoflood deposits at Yanjiapeng site in the upper reach of the Han River
    ZHENG Shuwei, PANG Jiangli, HUANG Chunchang, ZHA Xiaochun, LI Xin
    2014, 33(6): 799-806. https://doi.org/10.11820/dlkxjz.2014.06.008
    Download PDF ( )   Knowledge map   Save
    Through the stratigraphy and geomorphology investigation along the upper reach of the Han River, a loess-soil profile recorded palaeoflood slack-water deposits (SWD) was found at the riverbank near the Yanjiapeng site. This profile (YJP) was examined in great details in the field. The palaeoflood slack-water deposits samples were collected systematically and the grain size of the samples was analyzed in the laboratory. Results indicate that the grain size of the palaeoflood slack-water deposits shows a significant change in space. In the horizontal direction, grain size distribution, cumulative probability distribution and average grain size are the same in the same layer. In the top samples, the content of clay (<2 μm) is between 2.46%-2.97%, the content of silt (2-63 μm) is between 33.80%-44.50%, and the content of sand-sized particles (>63 μm) is between 52.66%-63.64%. The grain size distribution curves of these deposits are consistent in the same layer. In the vertical direction, however, grain size distribution, cumulative probability distribution and average grain size vary, and the grain size becomes smaller down from the top—the grain size distribution curves shift to the left gradually. The particle size of the peak position shows the following feature: top samples > middle samples > bottom samples. Some previous studies indicate that in the vertical direction the grain size of palaeoflood slack-water deposits becomes larger down from the top in the Wei River and Jing River. The results of this study at the YJP site in the upper reach of the Han River proved that the spatial variation of palaeoflood slack-water deposits has different forms. Similar grain size in the same layer indicates that the hydrodynamic force was basically the same in the horizontal direction and this result is good for sample collection in the field. The change of grain size in the vertical direction indicates that the hydrodynamic force was different and the reasons for this change may be related to the temporary river damming during the floods or the gradual built-up and quick withdrawal cycles of the palaeofloods. Samples should be collected layer by layer in the field study of grain size of palaeoflood slack-water deposits. If the palaeoflood slack-water deposits pinch out point cannot be identified in the field, grain size of palaeoflood slack-water deposits pinch out point of the same layer at close proximity can be used instead.
  • Quaternary Research
    Reconstruction and simulations for precipitation and atmospheric circulation over the past 30000 years in Asia
    LIAO Mengna, YU Ge
    2014, 33(6): 807-814. https://doi.org/10.11820/dlkxjz.2014.06.009
    Download PDF ( )   Knowledge map   Save
    Lake-level changes respond to variations in regional water balance and are sensitive to climate changes. Thus it has been one of the most important indicators applied to reconstruct precipitation and water budget. Tracing long-term lake-level changes can provide references to scientific prediction of catchment floods and droughts, rational utilization of lake water resources, and protection of lake ecological environments in Asia. As there was no observed data from pre-industrial time, almost all long-term precipitation and water budget reconstructions rely on geomorphologic, sedimentologic, biogeologic and archaeological records and so on. In addition, the construction of systematic lake level databases has facilitated regional climate change research of Asia for the late Quaternary. This paper summarizes and analyzes lake-level changes in Asia over the past 30,000 years and is composed of 4 sections. Section 1 introduces the history of Asian lake level studies, construction of indicator system and lake status database, and deep-lake drilling in Asia. Section 2 analyzes time sequences of four subregions of Asia (Middle East, Central Asia, Tibetan Plateau, and East Asia) lake-level changes and infers climate conditions from the time sequences. Section 3 focuses on the spatial patterns and climate mechanisms of two key climate periods (mid-Holocene, LGM). General circulation models (GCM) and regional climate models (RegCM2) were used to reveal spatial distribution patterns of mean annual temperature, precipitation and water budget (P-E). (1) 6-ka BP (mid-Holocene): the increase in the Northern Hemisphere summer insolation led to a temperature increase in the mid-and high latitudes in Asia. Significantly enhanced Asian monsoon induced the increase of precipitation in Arabian, Indian, and Tibetan plateaus. The reduction in precipitation over southern China was linked with adjustments in the position and strength of the Pacific Subtropical High. Annual convergences over Mongolia, north-northeast China, Tibet, and India indicated more moisture and frequently wet conditions. Conversely, divergences over southern China contributed to dry conditions. (2) 21-ka BP: Annual temperatures were generally lower than today. Less precipitation over most areas of Asia and negative P-E anomalies in the Southeast Asian tropical area and East Asian lowlands were due to a weakened Asian summer monsoon and a persistent winter Mongolian High. A southward and eastward shift in the position of the Westerlies plus a decrease in evaporation in the cool conditions that prevailed across Asia led to increases in annual precipitation and P-E in west China. Section 4 provides a brief account of the importance of Asia lake-level research to the understanding of environmental changes in the future and the uncertainties about the past lake-level changes.
    • Climate and Environmental Change
  • Climate and Environmental Change
    Influence of land use change on surface energy balance and climate：results from SiB2 model simulation
    LIU Fengshan, TAO Fulu, XIAO Dengpan, ZHANG Shuai, WANG Meng, ZHANG He
    2014, 33(6): 815-824. https://doi.org/10.11820/dlkxjz.2014.06.010
    Download PDF ( )   Knowledge map   Save
    The influence of land use and cover change (LUCC), by means of biogeophysical processes, on surface energy balance and climate is highly concerned by climate scientists. Driven by spatially interpolated meteorological data and remote-sensing derived leaf area index validated by on-site observations, the Simple Biosphere model (SiB2) was used to simulate the surface energy balances for different land use types, i.e. farmland, grassland and forest in northeast China, from 2001 to 2010. The SiB2 model validation was done by comparing simulation results with observed surface energy balance components and temperature in 2003 for the three land use types. The effects of LUCC on surface energy balance and climate was based on the average simulation outcomes in 2001-2010. Biogeophysical parameters (including albedo and roughness length), surface energy balances (net radiation flux, latent heat flux and sensible heat flux) and climate (canopy temperature) were analyzed to demonstrate the influences of LUCC. The results show that: (1) The simulated and observed data have similar annual trends (R2>0.42) but there is a gap of ±30 W/m2 for energy balance components and ±4 ℃ for temperature, based on annual averages. The model imitated the surface energy balance and temperature very well, and was used in the simulation of surface energy balance in northeast China. Sensitivity analysis revealed that the major influencing factor of surface energy partitioning was leaf area index, not vegetation cover as set in the SiB2 model. (2) The impacts of different land use types on surface energy balance and climate through biogeophysical processes were simulated using the same meteorological data for the purpose of eliminating the effects of meteorological conditions. The 10 year averages showed that albedo was lowest in forest, followed by grassland and farmland, while forest > farmland > grassland for leaf area index, forest < grassland < farmland for Bowen Ratio and forest > farmland > grassland for roughness length. (3) Trapped net radiation by ecosystem was primarily determined by albedo. Forest traps the highest net radiation, which is mainly allocated into latent heat flux; farmland traps the lowest net radiation, which is mostly channeled into sensible heat flux, and grassland is in between for both net radiation and its partitioning. (4) Canopy temperature (℃) was determined by the relative importance of albedo and the partitioning of net radiation into latent and sensible heat fluxes: forest (7.7)>farmland (7.64) > grassland (6.67), on annual average. The highest temperature of forest was decided by the lowest albedo, but the higher temperature of farmland as compared to grassland was caused by the higher Bowen ratio of farmland. (5) Precipitation was the predominant impact variable on surface energy balances, and was the main cause of the deviation of SiB2 simulation for forest. With the increment of precipitation in all three land use types, the net radiation flux partitioning into latent heat flux was enhanced, and that into sensible heat flux was weakened, as rain increases soil water content; at the same time, canopy temperature also decreased. The results of this research support the warming effect of farmlands converted from grasslands, which have taken place in northeast China over the past few decades.
  • Climate and Environmental Change
    Wind erosion in Xilingol League, Inner Mongolia since the 1990s using the Revised Wind Erosion Equation
    GONG Guoli, LIU Jiyuan, SHAO Quanqin
    2014, 33(6): 825-834. https://doi.org/10.11820/dlkxjz.2014.06.011
    Download PDF ( )   Knowledge map   Save
    Soil wind erosion is a major ecological environment problem in northern China. Xilingol League is located in the arid and semiarid areas. As one of the areas suffering from most serious wind erosion in northern China, its ecological environment is very fragile. Because of this environmental fragility, the area was included in the Beijing-Tianjin Dust Storms Sources Control Project that was officially approved by The State Council and implemented in 2002. In order to better understand the status of soil erosion and guide the regional desertification prevention, it is necessary to assess the variation of soil erosion and reveal the influences of weather and vegetation on soil erosion in Xilingol. In this study, based on wind speed, temperature, precipitation and other meteorology data, the normalized difference vegetation index, snow coverage and other remote sensing data, the Revised Wind Erosion Equation (RWEQ), which takes Newton's first law of motion as the foundation, was applied to evaluate annual soil losses caused by wind erosion. The results show that: The average soil erosion in Xilingol League between 1990 and 2010 was 0.34 billion tons. The intensity of soil wind erosion is low in most parts of Xilingol—these areas were mainly concentrated in the eastern, central and southern areas, where vegetation coverage is higher, wind erosion forces is lower, and rainfall is abundant. The areas with medium and higher intensity of erosion were mainly distributed in the Hunshandac desert of Suninteyou Banner, Zhengxiangbai Banner and Zhenglan Banner, where the soil is highly prone to wind erosion. Since the 1990s, soil erosion in Xilingol showed a deceasing trend. The reduction of wind erosion intensity is related to the weakened wind energy and improved vegetation cover. Wind erosion forces is the main driving factor of wind erosion—soil erosion was significantly correlated with the wind erosion forces (r=0.95, p<0.05). Wind erosion in Xilingol occurred frequently in windy springs. At this time, the effect of soil erosion associated with low vegetation coverage is most significant. Soil erosion was significantly correlated with the spring vegetation coverage in regions of higher wind erosion forces (r>0.7, p<0.01). Increased vegetation coverage effectively reduced soil wind erosion of the region in the recent 20 years. Low vegetation coverage makes the prevention of soil erosion more difficult and improving the grassland condition, especially in the spring season, is the key to controlling wind erosion of the soil. The RWEQ model was mainly used in the farmlands of the United States and cannot be directly applied in the grassland areas of China. In order to better apply the model in grasslands, the soil particle content was converted into the US system, surface roughness was measured by the roller chain method and withered vegetation coverage (obtained by photos) was introduced to replace flat residues on the surface of the soil. Even so, more research is needed to solve problems such as the influence of relief on soil wind erosion, the determination of noneroding boundaries, among others.
  • Climate and Environmental Change
    The extreme cold winter of 1620 in the middle and lower reaches of the Yangtze River
    YAN Junhui, LIU Haolong, ZHENG Jingyun, HAO Zhixin, GE Quansheng, FU Hui
    2014, 33(6): 835-840. https://doi.org/10.11820/dlkxjz.2014.06.012
    Download PDF ( )   Knowledge map   Save
    Climate extremes have become a hot topic in the field of climate change research. In this study, the snow-cover days over the middle and lower reaches of the Yangtze River (MLRYR) in the winter of 1620 were extracted from Chinese historical documents and archives. Using these records, the winter temperature anomalies (with respect to the 1961-1990 mean) of 9 stations were estimated based on the relationship between winter temperature and snow-cover days during the period with available instrumental observations. The regional winter temperature anomaly over the MLRYR was also estimated through stepwise regression. The results show that: (1) The regional mean snow-cover days for the middle and lower reaches of the Yangtze River were about 50 days, with high spatial variability. Snow-cover days ranged from 30 in Shanghai to 100 in Jingzhou, and the average snow-cover days were approximately 70 days in Hefei, Huoshan, Nanjing, Chaohu, among others in the region. Snow-cover days in Anqing, Wuhan, Changde, Changsha and Jingdezhen were 40 to 60, while the least snow-cover days of about 30 were found in Shanghai and southern Jiangsu Province. (2) It was extremely cold in the winter of 1620, and the regional mean winter temperature was estimated to be lower by approximately 4.4℃ than that in the period of 1961-1990. The maximum (coldest) winter temperature anomaly occurred in Jingdezhen, with winter temperature anomaly of about 5.7℃ lower than the reference period. The next were Huoshan, Hefei, Changde,Wuhan and Shanghai, with the winter temperature anomalies ranging between -5 and -4℃. Nanjing, Anqing and Changsha experienced smaller negative anomalies, ranging from -4 to -3℃. The minimum (warmest) winter temperature anomaly was detected in Changsha, but it was still much lower than the coldest record during the observational period.
  • Climate and Environmental Change
    Research progresses on the interaction between desertification and climate change in arid and semiarid East Asia
    HUATing, WANG Xunming
    2014, 33(6): 841-852. https://doi.org/10.11820/dlkxjz.2014.06.013
    Download PDF ( )   Knowledge map   Save
    Interactions between climate change and land surface processes, especially in arid and semiarid areas, have received increasing attention in recent years from climate scientists and geographers globally. In this paper, progresses in existing research on the interaction between desertification and the climate system in arid, semiarid, and semi-humid East Asia are outlined and discussed. Although there are large regional differences, the climate system affects regional desertification process by altering temperature, precipitation, wind field, and other meteorological factors. The current findings indicate that precipitation has a relative explicit impact on desertification: increases in precipitation are beneficial for vegetation growth and the reversal of desertification, and decreases in precipitation may result in increased desertification. Comparatively, the influences of temperature and wind field on desertification are more complicated and differ among various subregions: in the eastern monsoonal area, rises in temperature and the upper dominant southwest wind may be accompanied by increases in precipitation, contributing to reversals of desertification; in the western non-monsoonal area, rises in temperature promote increases in both surface evaporation and river runoff as a result of enhanced glacier thawing and snow melting, thus it is uncertain how this temperature change affects desertification; in the higher latitudes and altitudes, droughts and frost disasters often act together and give rise to severe damages to regional ecosystem, triggering increased desertification. On the other hand, desertification to some extent affects the local climate system by altering the characteristics of vegetation, land surface and soil. Increased desertification leads to vegetation degradation and subsequently changes in surface albedo, latent heat flux, as well as surface roughness height, which may in turn alter temperature, probabilities of precipitation events, and the wind regimes of local areas. Desertification also leads to the release of higher amount of fine particulates into the atmosphere, which may negatively affect the occurrence of precipitation. Overall, the interactions between desertification and the climate system include many feedbacks, among which the positive albedo-temperature-vegetation feedback and the positive sand-dust-precipitation-vegetation feedback are the principal mechanisms. Despite considerable progresses made in existing research, however, there remain many important issues that are yet to be addressed or difficult to address, such as the spatial and temporal aspects of processes involved in desertification, which are critical for understanding the interactions between climate change and desertification, and thus further studies are needed in the future.
  • Climate and Environmental Change
    Progress of research on forest land cover change in the Indo-China Peninsula
    LIAO Chenhua, FENG Zhiming, LI Peng, ZHANG Jinghua
    2014, 33(6): 853-864. https://doi.org/10.11820/dlkxjz.2014.06.014
    Download PDF ( )   Knowledge map   Save
    Forest cover is an extremely important natural resource in the Indo-china peninsula. It is of significant importance to the local ecological environment and socioeconomic development. This paper systematically summarizes and reviews research progresses on forest cover change in the Indo-china peninsula with respect to remote sensing monitoring and mapping, spatial-temporal variations, driving forces and ecological environmental effects, and discusses existing problems in these researches and trends of development. The results show that: (1) forest cover monitoring in the Indo-China peninsula have changed from optical remote sensing to radar remote sensing, and monitoring methods from single to multiple classifiers and data sources. The monitoring objects were mainly on natural forest covers, while monitoring of planted forests still face many difficulties; (2) forest cover area increased from 1980 to 1990 and declined since 1990. Among the five member countries of the Indo-China Peninsula, Thailand, Laos, Myanmar and Cambodia had decreased forest cover after 1990, while Vietnam is the only country where forest transition has occurred after the 1990s. The regional differences of forest cover change were significant in the Indo-China peninsula; (3) direct driving factors of forest cover changes were mainly cash plantation expansion, slash-and-burn cultivation, road construction and commercial logging, while indirect driving factors mainly included population change and socioeconomic and policy factors. The impacts on forest cover change were reflected in forest cover area, forest degradation/regeneration, and forest landscape ecology. The extent of impact was directly related to the pattern, intensity and frequency of disturbances; (4) the ecological and environmental impacts of forest cover change were mainly on water, atmosphere, soil and biology. Impact on water is focused on water retention of canopy and soil moisture regulating. Impact on the atmosphere is mainly on greenhouse gas emission and regional climate change. Impact on soil is largely on soil carbon emission and soil erosion. Biological impact is primarily on biodiversity. The forest cover change research in Indo-China peninsula has the following problems: (1) forest cover remote sensing monitoring was mainly on global area of forest cover, while studies on different forest types were rare, especially on local typical plantations. Research on forest degradation and regeneration was also inadequate; (2) the research of spatiotemporal patterns of forest cover change was mainly large-scale, while small-scale studies, especially comparative study of different countries or regions, were fewer; (3) research on the driving mechanisms of forest cover change was mostly qualitative or semi-quantitative, while integration of various data and quantitative analysis were inadequate. In view of these problems, future research on forest cover change of the Indo-China peninsula could be strengthened in the following three areas: (1) to explore or improve the monitoring methods of forest cover change, especially forest cover change in typical regions or typical forest types; (2) to enhance multi-scale, comprehensive and comparative study of forest cover change in the Indo-China peninsula; (3) to enhance quantitative study of forest cover change and the driving mechanisms.