Table of Content

    25 May 2005, Volume 60 Issue 3 Previous Issue    Next Issue
    Current Development Situation on Geographical Sciences and Resources Research
    LU Yongxiang
    2005, 60 (3):  355-360.  doi: 10.11821/xb200503001
    Abstract ( )   PDF (831KB) ( )   Save

    This article firstly emphasizes the relationship between geographical sciences and scientific viewpoint of development. Then the author summarizes some hot topics on geographical research in the fields such as water resources, urbanization process, regional development, greenhouse gas emissions and natural hazards. Finally some aspects were expounded, including orientation of geographical institutions, mechanisms for administering scientific research, geographical information technology, field stations construction as well as leadership, organization and human resource management in scientific research. This article is based on the report delivered by Lu Yongxiang, President of the Chinese Academy of Sciences, in the forum with the Institute of Geographic Sciences and Natural Resources Research on February 22, 2005.

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    A Study on Zoning "New Three Macro-Regional Development Zones" of Regional Economy of China
    LIU Yong
    2005, 60 (3):  361-370.  doi: 10.11821/xb200503002
    Abstract ( )   PDF (1486KB) ( )   Save

    With fast development of regional economy and society of China, the "Three Macro-Regional Development Zones", which is still in effect, is now hard to meet the requirements of the new situation under the guidance of integrated-considering regional development. According to the demands of the scientific viewpoint of development and the "five-integrated-considerations", after introducing what is a full regional economic system and the actual full four-layer regional economic system of USA, this paper puts forward a new zoning project of the "Three Macro-Regional Development Zones" and the 10 comprehensive economic districts of the regional economy of China: the "New Three Macro-Regional Development Zones" include the Northeast and East Coastal developing zone, the Middle and Near-Reach-West developing zone, and the Far-Reach-West developing zone; the 10 comprehensive economic districts are composed of the Northeast District, the Beijing-Tianjin-Hebei-Shandong Coastal District, the Shanghai-Jiangsu-Zhejiang Coastal District, the Guangdong-Fujian-Hainan Coastal District, the Upper and Middle Reaches of the Yellow River District, the Upper and Middle Reaches of the Yangtze River District, the Upper and Middle Reaches of the Pearl River District, Inner Mongolia District, Xinjiang District, and Qinghai-Tibet Plateau District.

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    Railway Network Organization and Spatial Service System Optimization in China
    WANG Jiao'e, JIN Fengjun
    2005, 60 (3):  371-380.  doi: 10.11821/xb200503003
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    This paper studies the relationship of network organization and spatial service system optimization based on analyzing the change of intercity passenger transport network behind railway's upgrading. The authors choose some indexes, including travel time and the coefficient of temporal location, to evaluate the benefits of 63 cities, accordingly to the reflection of the optimization and change of railway network structure. At the same time, the paper especially studies eight major transport harbors, including Beijing, Shanghai, Guangzhou, Zhengzhou, Wuhan, Shenyang, Chengdu and Lanzhou. Based on the analysis, we found that: (1) Intercity passenger transport network shows remarkable "time-convergence", an indication of the great optimization of the spatial service system. (2) The influences of optimization's spatial distributions are not equilibrium, the change of network structure is not remarkable, but it has the trend of equilibrium. (3) Railway's upgrading accelerates the interaction of cities, but the benefits of eight transport hubs are not the same, either; "500 km half a day of activity circle" has already taken shape, "1000 km a day of activity circle" and metropolitan transport circles such as Beijing and Shanghai are being developed gradually. (4) After the infrastructure network reaches the "universal" stage, the upgrading of network organization becomes more and more important to optimize the spatial service system, accelerate the economic interaction. (5) With the expansion of major hub cities' hinterlands and spatial service scopes, sequentially it will bring strong guidance to relocate economic action.

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    Situation and Suggestions of Sustainable Development in the Yangtze River Delta
    WANG Zhixian, YU Xiaogan, XU Kefeng, LIN Kang,
    2005, 60 (3):  381-391.  doi: 10.11821/xb200503004
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    The Yangtze River Delta has developed very fast since the 1990s. Its status ascends rapidly. Its GDP accounted for 12.53% of China in 1990 and increased to 19.45% in 2003. Since the 1980s, the courses of integrations in the Yangtze River Delta have been accelerated because of contacts among the enterprises and cooperations among the governments of different cities. The stage of omnibearing substantially associated development has started. However there are also some problems in the process of development. The whole level of FDI is not so high though it is large on scale. Farmland loss is serious in the region, for example, 300 thousand hectares of farmland were used for other purposes from 1990 to 2003, and the intensive degree of land in construction is lower. There is shortage in energy supply such as electrical insufficiency reaching 7.76 billion kilowatts in Jiangsu Province in 2002. Ecological environment is deteriorative, the pollution of water and atmosphere is very serious and geological disasters are also increasing. The water quality of stream channel and lakes in the Yangtze River Delta is type IV or V because of containing too much COD, BOD, N and P, except the water quality of the sources of the Yangtze River and Qiantang River, some reservoirs, and most parts of Taihu Lake, which belong to types II-III and can be perceived as drinking water source. In view of the level of industry, a considerable part of the Yangtze River Delta still needs to develop labor-intensive industries. So it is necessary to reinforce the development of labor-intensive industries while improving the level of industrial development in the Yangtze River Delta in the future. In order to keep healthy sustainable development of society and economy and keep consistency with the national goal of development, we must confirm the status of the Yangtze River Delta in regional economy and make a reasonable orientation of city function at first.

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    Spatial-temporal Changes of Urban Spatial Morphology in China
    WANG Xinsheng, LIU Jiyuan, ZHUANG Dafang, WANG Liming
    2005, 60 (3):  392-400.  doi: 10.11821/xb200503005
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    Fractal dimensions, compact ratios, shape indices and types of urban land expansion of 31 Chinese cities in 1990 and 2000 were computed by using dynamic land-use data from the National Resources and Environmental Database established by the IGSNRR, CAS. The results show, during the period from 1990 to 2000, that the type of urban land expansion belongs mostly to the 'extension' types and the cities with the 'filling' land expansion are almost located in the flat regions. Generally, fractal dimensions of 31 Chinese cities were inclined to reduce and fractal dimensions of the southern cities are more than those of the northern cities, compact ratios of most of the cities increased, urban shape indices of most of the cities decreased, during the period from 1990 to 2000. In all the 31 cities, the changes in the planar configurations of Guangzhou, Nanchang, Jinan, Chengdu, Beijing and Shanghai are the greatest, while the changes of Lanzhou, Taiyuan and Tangshan's configurations are the least. Such a simple rule is revealed that the fractal dimensions would reduce, compact ratio would increase and shape index would decrease if the type of urban land expansion belongs to the 'filling' type and vice versa.

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    The Spatial Characteristics of Shopping Behavior of the Chinese Urban Elderly: A Case Study of Beijing, Shenzhen and Shanghai
    CHAI Yanwei, LI Changxia
    2005, 60 (3):  401-408.  doi: 10.11821/xb200503006
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    Based on questionnaire survey on the daily shopping behaviors of the Chinese urban elderly, this paper compares the spatial structures of shopping behavior of the elderly in Beijing, Shenzhen and Shanghai. The authors also point out the general spatial characteristic of shopping behavior of the elderly in Chinese cities on a large scale. By aggregate analysis, it is indicated that the spatial characteristics of shopping behaviors of the Chinese urban elderly according to the distance decay law and its decrease ratio declines with the increase of distance. Based on comparable analysis, the authors find that the shopping behaviors of the elderly in Beijing decline firmly according to the increase of distance; the shopping behaviors of the elderly in Shenzhen decline in a fluctuating way with the increase of distance, expressing a spatial structure of "leapfrog concentration"; and the number of shopping activities of the elderly in Shanghai decreases most quickly. These differences have close relations to the development level of urban commercial establishments.

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    The Urbanization Model and Process in Bohai Sea Surrounding Area in the 1990s by Using DMSP/OLS Data
    HE Chunyang, LI Jinggang, CHEN Jin, SHI Peijun, PAN Yaozhong, LI Jing, ZHUO Li, Ichinose Toshiaki
    2005, 60 (3):  409-417.  doi: 10.11821/xb200503007
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    The paper firstly derived urban information from Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) data in 1992, 1996 and 1998 with the support of statistical data, then developed three basic urbanization models of polygon-urbanization, line-urbanization and point-urbanization in urban agglomerations from viewpoint of spatial analysis. The conclusions are as follows: (1) Urban patch numbers in the Bohai Sea surrounding area increased from 1659 to 2053 with the average increased number of about 66. Meanwhile, the small urban patches took over a large percentage in the region and the patch density increased fast. In addition, the urban barycenter of the region showed the trend to northeast from 1992 to 1998. The urbanization in the Bohai Sea surrounding area in the 1990s is fast and obvious. (2) The urbanization in the Bohai Sea surrounding area can be reflected by the polygon-urbanization around the big cities, the line-urbanization around the transportation lines and the point-urbanization emerging in the wide region. Of them, the polygon-urbanization was dominant. It is obvious within the 3-4 km areas surrounding the urban patches. The line-urbanization and point-urbanization in the region was relatively small, but both of them showed the obvious increasing trend.

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    Periodicity Scenarios in Metropolitan Region: A Case of the Baltimore-Washington Region in the USA
    ZONG Yueguang
    2005, 60 (3):  418-424.  doi: 10.11821/xb200503008
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    Urbanization is now recognized as a ubiquitous phenomenon of global importance. Traditional studies of urban and regional spatial sprawls usually pay much more attention to the sprawl processes of urban land use and seldom take account of natural landscape fragments and deforestation in general. This study tries to synthesize these two spatial processes by employing logistic competitive model in a case study. The sprawl process in the metropolitan area of the Baltimore-Washington is a typical organic growing process among corridors. By the 1790s, the major growths of urban area were around several growth poles. By the 1890s, the urban growths had begun along several corridors between Washington and Baltimore. By the 1990s, the urban growth was along both the growth poles and corridors so called network growth. It totally connected major corridors between Washington and Baltimore in 1992. This process can be described as "point-line-net-surface growth". What is interesting about this analysis is that the metropolitan growth seems to have a 30-40 year cycle by using logistic modeling simulation and circling the spatial area in particular. The period cycles included the low-speed developing cycle between 1792 and 1852, from the high-speed to low-speed developing cycle between 1852 and 1932, and the high-speed with turbulences developing cycle between 1932 and 1992. However, the expansion of urban growth has suffered from increased environmental pressure because of limited environmental capacities. They expand over agriculture, wetlands, wildlands, and forests, thereby changing the physical shape of the landscape as well as the functioning state of the landscape ecosystem. To solve these problems, "Smart Growth" initiatives have been promoted since the 1990s by increasing urban forest areas and constructing rural ecosystems in the Baltimore-Washington metropolitan region. We use the logistic model by adding competitive indices to simulate this process. Therefore, from the historical experiences of the metropolitan growth, the "Smart Growth" of metropolises must be favorable for the sustainable development of China metropolitan planning.

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    Features of Deep Trough at Tianjiazhen Reach and Its Impacts on Flood Discharge in the Yangtze River
    SHI Yafeng, ZHANG Qiang, CHEN Zhongyuan, JIANG Tong, WU Jinglu
    2005, 60 (3):  425-432.  doi: 10.11821/xb200503009
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    The width of the river reach near Tianjiazhen (23o55'N, 115o25'E), the middle Yangtze River, is only 650 m. The depth of this river reach is 90 m below the sea level of the Huanghai altitude, being the lowest place of the Yangtze River, which is about 30 km away from the river mouth. This narrowest width and the lowest depth is unique and intriguing. Some problems are put forward: what is the formation of this river trough and what is the role of this river trough on flood discharge. Geologic, hydrological and geomorphologic records and field investigation indicate that the horizontal length of this trough is about 8 km, which was formed by the NW-SE cut through an intensively folded range of thick Triassic limestone by the Yangtze River. Three small limestone hills near the river serve as the node, influencing the river flow patterns and causing accelerated river flow and whirlpools, the calcareous rocks are highly susceptible to the corrosion and intensified downward erosion, so that the deepest trough is formed. The life of this river trough is estimated to be several thousands of years. Recent repeated instrumental measurement results indicate that the river reach at Tianjiazhen is in minor changes in erosion and sedimentation with relatively stable channel shapes. The river trough exerts no influence on flood discharge during the normal water runoff; while it plays a significant role on flood discharge when the runoff exceeds 50 000-60 000 m3/s.

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    Study on the Characteristics and the Cause of Sandy Desertified Land in the West of Hainan Island
    LI Sen, SUN Wu, LI Fan, LIN Peisong, ZHENG Yinghua, NIE Lei
    2005, 60 (3):  433-444.  doi: 10.11821/xb200503010
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    The west of Hainan Island is the only sandy desertified area of the tropical dry grasslands with sparse trees in China, and it is a very typical sandy desertified land type and course. The sandy desertified land, which is on the sandy coastal plain, the river delta and the sandy mesa, is distributed in the long and narrow area. The sandy desertified lands have the tropical coastal dene characteristics in the district, the shape, the xerophyte and the rapid evolvement of land use. Under the influence of tropical monsoon climate, the foehn effect of the rain shadow field of the Changshan Mountains and the Wuzhishan Mountains and the cold ocean current in the Beibu Gulf, it is developed into the semi-arid climate and the environment of dry grasslands with sparse trees. So that it comes into being for the driving force, the space and the material base of the desertification. The sandy desertified land in the west of Hainan Island in history is due to many factors such as the climate change, the excessive reclamation and excessive firewood, but the factor of human leads the first. The present-day sandy desertified land in the west of Hainan Island can be divided into five stages of increase, renewal, re-increase, reversion and fluctuation in the 20th century, its process is not only controlled by the climate change in several years or decades scale, but also the unreasonable human activities. The area of sandy desertified land increased from 201.45 km2 to 251.61 km2 from the end of the 1950s to the 1970s with an increasing rate of 3.53 km2/a. It has decreased to 122.57 km2 since the 1990s with a decrease rate of -7.72 to -3.20 km2/a. The temperature in the west of Hainan Island appeared to go up by 0.24 oC/10a and the precipitation descended by -23.93 mm/10a for the past 50 years. The land resources are being excessively exploited because of continuous increase in population and domestic animals in recent decades. The results show that the human activities are greatly associated with desertification degree, and the present-day sand desertification in the west of Hainan Island has evolved into the desertification process which is mainly affected by the human activities.

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    Danxia Landform Genesis on Qiyun Mountain, Anhui Province
    ZHU Cheng, PENG Hua, LI Shicheng, HUANG Linyan, ZHENG Chaogui, XIANG Fusheng, SUN Yufei, TANG Yunsong, HU Jiyuan, ZHU Guanghui, LU Jianjun, CHENG Guanghua
    2005, 60 (3):  445-455.  doi: 10.11821/xb200503011
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    The Danxia landform of Qiyun Mountain is mainly developed on red sandstone and conglomerate of middle Cretaceous series (K2x1). The landform development in this area is mainly controlled by three faulted zones, that is, Jingdezhen-Qimen faulted zone, Jiangwan-Jiekou faulted zone and Kaihua-Chun'an faulted zone. During the Cretaceous period, this area firstly experienced massif subsidence to a continental fault basin, and received thick Cretaceous red beds to accumulation. Then, during neotectonism, this area experienced an uplift process, the thick Cretaceous sediments became a mountain body with an altitude of 500-600 m. After having undergone the processes of vertical joints development, weathering, denudation and transportation, as well as influenced by the lithological component and structure between the sandstone and the conglomerate, grand Danxia landscape has formed in this area such as peak forest, steep cliff, cave, mesa, castellated peak and natural bridge. The three-grade knick points of Qiyun Mountain illustrates that the area has experienced three major uplift processes during the neotectonism.

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    Impacts of Land Use Changes on Groundwater Resources in the Heihe River Basin
    WANG Genxu, YANG Lingyuan, CHEN Ling, Jumpei KUBOTA
    2005, 60 (3):  456-466.  doi: 10.11821/xb200503012
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    Land-use and land-cover changes have great influence on the regional hydrological process. With three periods of remote sensing data since the 1960s and the long-term observed data of groundwater since the 1980s, the impacts of land-use and land-cover changes on the groundwater system in the middle reaches of Heihe River Basin in recent three decades are analyzed with the aspects of groundwater recharge and discharge system. The results indicate that with different intensities of land-use and land-cover changes, the impacts on the recharge were 2.602×108 m3/a and 0.218×108 m3/a in the former (1969-1985) and latter (1986-2000) fifteen years and those on the discharge were 2.035×108 m3/a and 4.91×108 m3/a. As long as under the reasonable range of exploitation (less than 3.0×108 m3/a), the land-use changes would control the changes of regional groundwater resources. Influenced by the land-use and land-cover changes and the large-scale exploitation in the recent decade, the groundwater resources present apparent regional differences in Zhangye Basin. Realizing the impact of land-use changes on groundwater system and the characteristics of spatial-temporal variations of regional groundwater resources may make the programming and management of water and soil resources more scientific and reasonable.

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    NDVI Reflection of Alpine Vegetation Changes in the Source Regions of the Yangtze and Yellow Rivers
    YANG Jianping, DING Yongjian, CHEN Rensheng
    2005, 60 (3):  467-478.  doi: 10.11821/xb200503013
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    The spatial distribution and dynamic change of vegetation cover in the source regions of the Yangtze and Yellow rivers of the Tibetan Plateau are analyzed in recent 20 years based on 8 km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 2001. The data are from NASA Pathfinder AVHRR Land datasets. On the basis of simple correlation analysis of air temperature, precipitation, shallow ground temperature and NDVI, which is 3×3 pixel at the center of Wudaoliang, Tuotuohe, Qumalai, Maduo, and Dari meteorological stations, the statistical models of air temperature, precipitation, shallow ground temperature and NDVI are constructed in this paper under two conditions—considering ground temperature action and not considering ground temperature effect. The results show that as a whole vegetation cover keeps original conditions basically in recent 20 years, vegetation continues to degrade in local areas of the source regions of the Yangtze and Yellow rivers. Remarkable decrease regions in NDVI are Zhaling Lake and Eling Lake edges, areas to the east and the north of the lakes, the headwater area of Duoqu river in the northern foot of Bayan Har Mountain in the source region of the Yellow River, part areas in Geladandong region, some regions along the Qinghai-Xizang Highway between Tuotuohe and Wudaoliang, Qumalai and Zhiduo belts in the source region of the Yangtze River. Decrease range of NDVI is 0% to 20%. Vegetation degraded very severely in the above-mentioned regions. In the source regions of the Yangtze and Yellow rivers annual NDVI changes, namely good or bad vegetation cover is influenced mainly by temperature, especially near 40 cm ground temperature below the earth surface. NDVI is very sensitive to near 40 cm ground temperature change. Permafrost is widely distributed in the source regions of the Yangtze and Yellow rivers. Its freezing-thawing processes are not only associated with ground temperature change, but also affect soil water content. Permafrost degradation will influence directly alpine vegetation growth in the source regions of the Yangtze and Yellow rivers.

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    Mapping Method of Eco-Environmental Remote Sensing Complex Series
    LIAO Ke
    2005, 60 (3):  479-486.  doi: 10.11821/xb200503014
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    This paper proposed the method of ecological environmental remote sensing complex series mapping based on GPS, RS, GIS, and field integrated investigation and remote sensing images comprehensive interpretation. According to different types of ecological environment in mapping area and different characteristics of Landsat image and its tone, field integrated investigation was conducted to analyse the characteristics of ecological environment types and geomorphology, vegetation, soil and land use of the observation point and its surrounding areas, to interpret the satellite image tones and characteristics, and to find out the direct and indirect marks of interpretation. The first step of mapping is composition of the boundaries of ecological environmental unit in the seeable area, and record the ecological environmental types and coding of various elements. After field integrated investigation, based on reorganization and comprehension of the mapping area, the satellite image interpretative marks were controlled and established. The geographic methods of interpolation and extension were adopted to interpret satellite image. Finally, the ecological environmental unit boundary map was compiled for the whole mapping area. The second step concerning GIS process date and derivation with the aid of computer will automatically compose thematic map of various elements of geomorphology, vegetation, soil, land use and ecological environmental types. This method can not only improve the quality of complex series maps, but can also quicken the map making procedure, which is also convenience for comprehensive analysis and evaluation, especially for setting up unit and data base of geographic information system and ecological environmental information system.

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    The Dynamic Variation of Water Resources and Its Tendency in Tarim River Basin
    XU Hailiang, YE Mao, SONG Yudong, WEI Jun
    2005, 60 (3):  487-494.  doi: 10.11821/xb200503015
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    The method of time series is applied to analyze the variation of precipitation and temperature from 1961 to 2002 in the mountainous areas of the Tarim River Basin, as well as water consumption in the headstream and mainstream areas. Those hydrologic parameters are verified. Quantitative results indicate that the precipitation and temperature in the headstream areas have an increasing trend to different extents. The increasing trend of precipitation is less significant than that of the temperature (α = 0.05). Runoff of three headstreams also increased especially from 1994 to 2002. Compared with the perennial runoff, the annual runoff has increased by 25.163×108 m3/a. However, inflows of the mainstream areas have only increased by 0.9985×108 m3/a. So the runoff at different hydrologic stations in the headstream areas has a linear decreasing trend. It is shown that the degraded trend of ecological environment of the Tarim River Basin hardly changes in the special water period for continual ten years. Given runoff of three headstreams is accounted in the normal period from 1957 to 2003, the annual runoff of the headstream areas would be only 22.57×108 m3. The ecological safety problem of the Tarim River Basin will be paid attention to in current situation.

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    Fractality of Grain Composition of Debris Flows
    LI Yong, CHEN Xiaoqing, HU Kaiheng, HE Shufen
    2005, 60 (3):  495-502.  doi: 10.11821/xb200503016
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    Debris flow is in essence the process of mass transportation controlled by its constitution that can be characterized by a wide-ranged distribution of grain size. Soil samples of debris flows of various densities have been collected from different regions and gullies. Analysis of grain composition, particularly for debris flow of high density, ρs > 2 g/cm3, reveals that the cumulative curve can be fitted by exponential function with exponent varying with regions and gullies. More importantly, the exponent falls into a narrow-valued domain and hence provides an index signing the activity of debris flows. Furthermore, fractality turns out to exist in grain composition and porosity; and fractal dimension has been derived from cumulative curves in a certain range of size, a range that defines the upper limit of grains constituting the matrix of debris flow. In analogy to concentration in fluidization of granular materials, fractal structure of porosity has proved to take a crucial part in initiation of debris flows.

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    The Evolution of Annual Runoff and Sediment in the Dongting Lake and Their Driving Forces
    LI Jingbao, WANG Kelin, QIN Jianxin, XIAO Hong, CHAO Liyi
    2005, 60 (3):  503-510.  doi: 10.11821/xb200503017
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    Some conclusions drawn from multianalysis of the evolution process of annual runoff & sediment and the driving forces in the Dongting Lake from 1951 to 1998 are as follows: Runoff and sediment connect with each other closely and the related modulus is 0.9013. Annual runoff volume and annual sediment discharge as a whole take on a synchronously-decreasing trend, and the evolution process is characterized by obvious stages. Because the major catchments of Xiangshui, Zishui, Yuanshui and Lishui drainage basins and the high forest-covering-rate above 52%, the newly built water conservance projects in recent years and the increase of industrial, agricultural and domestic water consumption cannot exert fundamental influence on the hydrological characteristics of the four rivers and the runoff and sediment flowing into the lake are basically stable, so they do not have profound effect on the runoff and sediment in the lake. The three-time adjustment of of water-sand relations of the rivers and the lake resulting from the pluging up of Tiaoxian bayou on the midlle reaches of the Yangtze River, the curve-cuttings in the lower Jingjiang River system and the flow-cutting at Gezhouba dam, however, become the main factor leading to the deceleration of the runoff and sediment in the Dongting Lake.

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    Use of Cokriging to Improve Estimates of Soil Salt Solute Spatial Distribution in the Yellow River Delta
    WANG Hong, LIU Gaohuan, GONG Peng
    2005, 60 (3):  511-518.  doi: 10.11821/xb200503018
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    Estimation of the quantity and distribution of soil chemicals is a major component in the study of chemical transportation in the vadose zone and groundwater system. Such information is also essential in undertaking any proper measures to meliorate soil salinization. However, it is a time-consuming, laborious, and expensive process to carry out detailed sampling in the field, especially when it is large. Accurate variability of soil solute can be determined from a limited number of the available samples through geostatistical analysis. In this study two interpolation methods (ordinary kriging and cokriging) were compared with each other in terms of their accuracy. It is found that cokriging of half of the observations (239) resulted in more accurate results than ordinary kriging of all the samples. Cokriging is able to reduce relative root mean square error (RMSE) by 130.83% in comparison with ordinary kriging. Using the same number of samples (239) for the secondary variable (total salt), cokriging attained a higher accuracy with half of the samples than it did with all the samples, the relative reduction of RMSE being 20.10%. Furthermore, the relationship between the secondary and the primary variables governs the estimation accuracy. As the correlation coefficient between them increases from 77% to 99%, the relative RMSE of estimation is reduced by 48.30%.

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    Field Survey on Water Erosion of the Rural Settlements in the Loess Hilly-gully Area of Northern Shaanxi Province
    GAN Zhimao, YUE Dapeng, GAN Rui, ZHA Xiaochun
    2005, 60 (3):  519-525.  doi: 10.11821/xb200503019
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    After observing the soil erosion of rural settlements formed by rainfalls (water erosion) based on field survey in northern Shaanxi province, this paper draws the following conclusions. (1) The average runoff coefficient of rural settlements is 0.335. The maximum runoff coefficient is 0.44, which exists in Yan'an county. The runoff coefficient in Yulin city and Suide county is 0.293 and 0.272 respectively, relatively small. Among the land-use types of rural settlements, the runoff coefficient of road land and yard is greater (separately 0.39 and 0.377), and the runoff coefficient of open space between houses is smaller (0.277). (2) The average runoff-contained sediment amount of open space between houses is the greatest (52.54 g/L), that of settlement yards is the smallest (17.19 g/L), and that of road land is placed in the middle (41.42 g/L). (3) The average erosion intensity of the rural settlements in northern Shaanxi Provence is 5434 t/km2·a, falling into the category of severity erosion. The erosion intensity of road land and open space between houses is respectively 7348 and 6873 t/km2·a, greater than that of the settlement yard (2081.7 t/km2·a). (4) The change of soil erosion of rural settlements is affected more prominently by human activities. It concludes that soil erosion of rural settlements on the Loess Plateau is quite severe and has its particularity. Therefore it can not be ignored and must be paid attention to its research and prevention.

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