One important role of high speed transportation network is to promote the spatial agglomeration of traffic flow, which leads to changes of spatial interaction. Air transportation in China grew rapidly in the past two decades and is playing more and more important roles in state transportation system. Due to the improvement of aviation service and the expansion of air transport network, the inter city linkages among domestic cities are getting enhanced, and hierarchical network is taking shape. In this paper, air passenger network in China is analyzed. The results of dominant flow analysis indicate that the air passenger flow between cities increased quickly in the past two decades, and “Hub and Spoke” network has been formed basically. Beijing, Guangzhou and Shanghai are the most important hubs in China's domestic air passenger network, and Urumqi and Kunming are important local hubs. According to the statistical analysis, the passenger flow between cities is closely related to the distance, urban scale, and urban function. In China, about 90% of domestic air passenger traffic takes place between cities where the inter city transport distance is less than 2 400 km. In order to raise the efficiency of air transportation system, it is very important to organize the passenger network between hub and local airports.

The pathogens, epidemiology, prevention and control of plague, a deadly infectious disease most harmful to human beings are all highly related to physical and human factors People still have not completely understood some facts concerning plague epidemic formation and its relationship with eco-environment Hence it is very important to study the geographical epidemic law of plague and distribution of plague natural foci, and analysis on their environment-health vulnerability for more effective control of its outbreaks and epidemics The assessment of environment-health vulnerability will present a synthesis analysis talking human health as the core This paper firstly presents the background of spatial distribution of plague and natural plague foci in whole China,and then studies the environment health vulnerability by taking a typical plague focus as a case Chifeng in Inner Mongolia, a typical dauricus plague focus, and one of the ten types of natural plague foci in China, was selected for study based on 13 natural and social indicators such as rat density, annual average rainfall, annual average temperature, forest coverage, meadow coverage, population etc For the purpose of analyzing the trend of environmental change and its impacts on plague prevalence, the threshold value of environment-health vulnerability was deduced through clustering analysis and matrix operation of 13 indexes, and 4 different types of environment-health vulnerability were divided according to the threshold value Corresponding to this, 4 types of environment-health vulnerable areas in the typical plague foci, such as very high vulnerable area, high vulnerable area, moderate vulnerable area and low vulnerable area were identified The characteristics of low vulnerable area mainly manifested higher forest coverage or high urbanization level where it was unsuitable for dauricus survival anymore Consequently, the risk of plague prevalence changed into very low possibility On the contrary, the original surroundings in the very high vulnerable area became deteriorating seriously, and it posed higher probability of plague prevalence These imply that rehabilitating environment status in plague foci is the essential way to improve the environment-health vulnerability and control plague prevalence effectively

Based on the data, which were obtained weekly at 24 sites along a transection set up in the Eastern Shore of Nanhui from Apr 1999 to Apr. 2000, this article quantificationally examines the cross shore differences of annual vertical accretion rate, absolute and relative stabilities of sediment surface. The results are as follows: (1) The annual vertical accretion rates are distinctly different at each site along the transection with a maximum of 49.5 cm/a at the site where the submergence probability is about 30% (between the average neap high water level and the average high water level) and a minimum of 2.2cm/a at the site near the seawall. The maximum is 22 times of the minimum. The annual vertical accretion rate is comparatively low where the marsh and the bare flat meets. Totally, the annual vertical accretion rates are lower at sites on the bare flat than those at sites on the marsh. (2) The absolute stabilities of the sediment surface are different at each site along the transection. Because it indicates the same phenomenon as the annual vertical accretion rate does, the difference of absolute stability is in accordance with the difference of the annual vertical accretion rate along the trasection. (3) The relative stabilities of the sediment surface are different at each site along the transection. The relative stabilities are much stronger at sites on the marsh than those at sites on the bare flat. (4) Vegetation plays an important role in protecting the shore from erosion and stimulating accretion It also enhances the relative stability of sediment surface The difference in short term evolution of intertidal muddy flat is a compositive reflection of the submergence probability, energy of the wave and tide as well as the distribution of vegetation along the transection

Although the international societies, as well as countries throughout the world, have stressed food security and its conditions have been improved considerably since the 1970s, the future state will still be very severe because of population increase and agricultural productive condition deterioration. As to China, the productivity has been rising since the Reform and Openness. Chinese have gone out of the epoch of food shortage and the general level of food security has also improved substantially. But, there are still many factors restricting Chinese food security, such as population increase, productive resource shortage and so on. Therefore, to sustain China's food security is vital to realize Chinese social, economic and natural sustainability. Food productive and supply level, food structure diversity, habitant earning level or obtaining ability to maintain survival and other factors jointly affect food security level. In this paper, the meaning of food security is firstly discussed. Basing on fundamental factors influencing food security, the authors then select a set of evaluating indicators, formulate an integrated index evaluation model on food security. Using the evaluation model, food security integrated indexes covering 1950～1998 are calculated thirdly. A single-factor and multi-factor integrated evaluation on Chinese food security sustainability is carried out finally. The calculated results show that China was in a generally secure state of food in the 1950s, in an insecure state of food in the 1960s and the 1970s, and had entered a steady secure state of food in the 1980s through to the 1990s. Since the 1960s food security level in China has been rising year after year and since the 1980s a sustainable development trend has been maintained.

In the paper, based on the LandsatTM/MSS data in 1975, 1984, 1991 and 1997, the land use/cover change in Beijing area was examined with the support of RS and GIS. Conclusions of the study are drawn as follows: The large-scale land use/cover change took place in Beijing area in the process of rapid urbanization from 1975 to 1997 with major characteristics of urban expansion at the expanse of encroaching cultivated lnad in the plain area and of obvious structural readjustment occurring in other land use/cover types. There existed obvious regional difference in land use/cover change in Beijing area during the past twenty-odd years and the land use/cover change rate in exurb has already exceeded that in suburb in the 1990s. With drastic land use/cover change in the region, the barycenterof the high-density urban land moved to the northwest to certain extent during the past decades, showing that the urban land use density in the west and northwest of Beijing city improved obviously with the expanding trend to the west and northwest in the same period.

Looking from regional point of view and based on the analyses of the environmental regional structure and socioeconomic structure of coastal zone of Yellow Sea, this article discusses their interrelations and defines the leading direction on socioeconomic control for improving environmental quality in different regions.

The data used in this paper are collected during four field surveys, in which measurements at various stations (Fig 1) have been carried out The measurement periods cover December 18-19, 1982 (dry season, spring tide), September 7, 1983 (flood season, spring tide), July 29, 1988 (flood season, spring tide) and December 24, 1988 (dry season, spring tide) Analysis was done by combining the observed data with research results of others According to calculated values of the dominant flow, the Changjiang Estuary can be divided into three types of sections with different characteristics The first is mainly influenced by river flow, or ebb dominant flow section; the second is mainly influenced by tidal flow, or flood dominant flow section; and the third section is dominantly influenced by the density flow In areas with ebb dominant flow, the residual sediments from upper lager to lower layer transport seaward; in areas with flood dominant flow the residual sediments from upper layer to lower layer transport landward; and in reaches with density flow dominated section, the residual sediments transport to the upper layer, which would be carried seaward with the outflowing river water, but in the lower layer it is done in the flood direction Moreover, there are other forms to transport residual suspended sediments: Sediment exchange between channel and tidal flat is caused by horizontal circulation flows Sediment of the North Branch has turned to the South Branch and sediment of the South Passage has turned to the North Passage According to the depositional areas and under water depositional morphology, four types of deposition are :dentified:1)Underwater sandbank formed by diversion of flood and ebb flow; 2)in areas with dense flow dominated section, due to the mixtrue of salt and fresh water formed the turbidity maximum, the mouth bars have the same location as the turbidity maximum; 3)the deposition of the large amount of the suspended sediment is growing into huge submerged delta out of the estuary; 4)and the marshes developed by the horizontal circulation of flow and sediment transport at the channel tidal flat systems

According to the statistical and survey data at provincial and county levels, trend of cultivated land change and its driving forces in Shandong Province during the last 50 years are discussed in this paper. It was found that (a) since the 1950s, the total area of arable land and per capita availability are reducing. For example, the total area under cultivation reached its top in 1955, and declined after the year of 1955. Per capita cultivated land decreased nearly in a straight line year after year and changed from 0.192 hm 2 to 0.075 hm 2 ,and the trends of decrease will continue with further development of economy and increase of population; (b) according to the GIS spatial analysis, the movement of the gravity center and the relative change indices of the cultivated land in Shandong Province have regional differences, the change is smaller in the eastern part than that in the central-western, the distribution core of the cultivated land in the whole province has been shifted 10.62km northeastward; (c) as a result of the principal component analysis, the eight driving forces variables affecting arable land changes were analyzed which could be classified into three types, i.e., the dynamic development of economy, pressure of social system and progress of science and technology in agriculture. As to the specific factors, per capita net living space, population and yield of grain per ha are the main driving forces, which play an important role in the changing of cultivated land;(d) by using regressive equation, along with population growth and economic development, the prediction of cultivated land in Shandong Province is done for 2005 and 2010, the prediction result is that Shandong's farmland area will be 6 435.47×10 3hm2 in 2005 and 6 336.23×10 3hm 2 in 2010. The analytical results and conclusions of this paper will provide scientific basis for sustainable agricultural development in Shandong Province.

Basing on the methods of sporo pollen analysis, analysis of arenaceous quartz surface and soil micromorphology, this paper deals with the genetical properties of the albic soils in the Jiang Huai Area in the Northern Subtropical Zone of China. The spore pollen analysis shows the differences between the upper and the lower horizons in soil forming environment. The upper horizon underwent warm temperate forest steppe landscape and subtropical steppe landscape, which belonged to high chemical energetic environment. After the deposition of parent materials, the soil experienced brown soil process or deposition of other materials,then the deposition suspened for long period of time.With the accumulation of new deposits and climate change, the soil forming environment became the subtropical steppe landscape.The basic condition emerged for the formation of yellow brown soil in higher land,and the lower part became marshland with inadequate water drainage. The form of the arenaceous quartz includes its surface shape and structure, and reflects the obvious differences in soil forming environment between the upper and lower horizons. The surface of arenaceous quartz in the lower horizon, especially the illuvial horizon, generally has secondary SiO 2 sediment. As the surface decomposed, some holes formed along the weak region in the quartz sand, and this behavior stands for the high chemical energetic environment. Since the materials constantly deposited and water concentrated, no high chemical energetic environment appeared in the upper horizon. The diffuse and stress stick membranes are found in the thin section of the soil micromorphology.These membranes are the sigh of the secondary clayization.The fabric and light directioal clay membranes formed in the alluvial horizon for the accumulation of clay. Overall,when the Xiashu loess and other loess materials deposited, the climate was the warm temperate forest steppe zone, it then became the northern subtropical forest steppe zone.Finally,the new materials accumated over the loess derived soils.On the bases of the superipositing parent materials,the lower horizon is now at the secondary clayization stage and after the new materials superimposed,the alluvial horizons will have illuviation of clays.

The concentration of the atmospheric CO_{2, one of the most important greenhouse gases, is increasing since the beginning of industrialization from its pre-industrial value of 280ppmv to its present value of 366ppmv. It has been proved that human activities, including fossil fuel burning, cement production, and land-use change, have severely disrupted the model of the carbon cycle, thereby alter the climate system and affect the processes and mechanisms in terrestrial ecosystems. Understanding the consequences of these changes in the coming decades is critical for the formulation of political, economic, energy, and security policies. So recently,studies in carbon cycle have increasingly become a focus of global change and geo-science in the world. The terrestrial ecosystem,one of the most important parts of the global carbon cycle, is most complex and most greatly affected by human activities. This paper, combined with the latest reports related to carbon cycle in IGBP and IPCC, introduces some major carbon pools, namely, lithosphere, atmosphere, ocean,and terrestrial ecosystem,in the global carbon cycle and their sizes and characteristics. Furthermore, four major approaches, including inventories method, eddy covariance measurements, inverse modeling and model of carbon cycle, which have been used to evaluate the biosphere-atmospheric exchange of CO2in the terrestrial ecosystems,are introduced. Using inventories method we can get an estimate of the actual accumulation of carbon in terrestrial ecosystem. The eddy covariance approach can detect small changes in net CO2exchange between terrestrial ecosystems and the atmosphere over various time scales. Inverse modeling approach can be used to infer carbon sources or sinks based on 3-D atmospheric tracer transport models and CO2 records from the atmospheric observations, fossil fuel combustion and land use change. Model of carbon cycle is a powerful tool to estimate and evaluate the temporal and spatial patterns of carbon sources or sinks in various scales. The existing problems of using these four methods are also analyzed. Moreover, the uncertainties in terrestrial carbon process are analyzed particularly.Additionally,some problems unsettled in carbon cycle and development tendency are specified concisely.}

Beijing is one of the ancient cities in China. In history, land use and land cover in its territory changed with intensities of human activities. The most striking land use change is the expansion of urbanized areas no matter fast or slow in different periods. Its historical development process could be roughly divided into two periods in this paper, one is from Liao Dynasty when Beijing initiatively became the capital to 1911 when traditional China ended. Another period is from 1911 to the present, particularly from 1949 to 1997 on which the discussion on land use and cover change is focused. The period of 1949 to 1997 could be divided into two sub-periods, i e , planned economy period from 1949 to 1978, and the institutional and market oriented transition period from 1978 to the present. Through the brief discussion, we can see that land use/land cover change has been accelerated in the past 100 years, especially in the past 50 years because of the changes of social ideologies, policies, population growth, technological improvements and the strengthening of economic power. More detailed and quantitative studies of the relationship between those social-human factors and the urbanization as well the land use/land cover change need further studies in the future. The consequences of land use and cover change in Beijing, the future development trends of the city and some related issues are also discussed in the paper.

This paper focuses on the discussion of the urbanization territorial modal of transport junction and its hinterland. Firstly, taking some cites as an example, the paper briefs the general characteristics of transport junction site. Then, it discusses dynamic mechanism between urban function formation and urban scale expansion, and capture process of hinterland and changes of urban region relationship. After that it summarizes a four phase dynamic model of urbanization development in transport junction and its hinterland. Finally the paper puts forward strategic trajectory and principal countermeasures for urbanization development in these regions.

Lancang River is a mountain river Its river boundary is mainly composed of bedrocks and the alluvial material can only be found in a few slightly wide reaches Generally, suspended load is in unsaturated state, and bed load becomes important sediment movement Owing to lack of real bed load data, it is very difficulty to study scouring and silting changes of the Lancang River In this paper, we use the survey data of the individual sections and compare their areas at different durations, then analyze their correlation to the coefficient of incoming sediment The results show that: (1) change amplitude of scouring and silting is not great, the accumulated change amplitude of Yunjinhong section during more than 20 years is only 20.2m²and of Jiuzhou section is only 2.05m²(2) there is a kind of, but not very good correlation of change amplitude of scouring and silting to coefficient of incoming sediment When the coefficient of the incoming sediment increases, silting happens, conversely, scouring happens Based on these results mentioned, the future development tendency of scouring and silting changes is also studied Two possibly happened environmental changes are considered in the study, increase of the incoming sediment caused by increasing human activities and a series of water conservancy projects will be built Because changing direction of these two is inverse each other, the scouring and silting change of the Lanchang River is approximately the same to the present situation .

The man earth areal system is the nucleus of the research in geography. It has very important influence on knowing connotation of the sustainable development for the theoretical research and practice of man earth areal system. At the same time, the man earth areal system itself must be developed, so the abundant and philosophical connotation of the sustainable development would be promoted. In the more and more not knowing about the thinking of the sustainable development in the world today, the article studies the interactive mechanism of man earth areal system and the sustainable development, than discusses the essence of development of man earth areal system, the essence of the sustainable development, background of space and time of man earth coordinated development, and philosophic essence of the interactive mechanism of the two developments. It concludes that the full and necessary conditions of the two developments helping each other should consist of selfless realm of thought in the human society, human spirit merging with physical geographical environment, specially the philosophic thinking of existentialism of self disciplined and self examined critically possessed by ancients We can see that the philosophical significance reoccurs the connotative way development landscape of the man earth areal system.

The Foothill Belt in the northern slope of the Tianshan Mountains is a transitional znoebetween mountains and plains.It is about 400 km long and 60 km broad from Wusu city to Jimusar city, appearing in three rows of folds with different morphologies and with their age becoming younger from south to north. Based on Geological Information System (GIS) and Remote Sensing (RS) methods, as well as previous research results, this paper systematically discusses the effects of foothill belt on hydro process in plain area. There are four facets of effects. Firstly, the foothill belt can prevent shallowgroundwater from flowing into plains directly, and turn it into surface water flow so as to increasestream runoff. The percentage of groundwater to surface river flow with foothill belt can reach about 47%, but percentage of groundwater to that without foothill belt is only about 37%. Secondly, the foothill belt can enhance annual adjustment abilityof surface rivers, making oasis developsteadily, e.g. the oasis area is about 7 539km 2 in ManasRiver basin with foothill belt is available, but in Sikeshu River basin, the foothill belt oasis area is only about 134km 2 . Thirdly, the foothill belt can prevent floodwateror mud rock flow from entering into plains directly and protect oasis safety. Fourthly,the foothill belt can affect distributions of aquifer'soverflow and buried depth of groundwater level in the plain area,and can control spill amount of groundwater. The foothill beltis importantto surrounding environment, as it can protect the surrounding ecoenvironment, influence land use and land cover change in the plains. Every vertical spectrum with foothill belt is100～200m lower than that without foothill belt. The purpose of this paper is to affer anew understanding about the foothill belt andits functions to environment, especially to hydro process in the plains, and a new idea about how to study interaction between highland and lowlandor mountains and plains. And it can provide scientific basis for utilizing water resources rationally and achievingsustainable development of oasis.

Based on the data up to 1999 from the hydro-climatological departments, this paper analyzes the climatic dividing implications of Qinling Mountains in regional response to the process of global warming, due to which the Grades of Dryness/wetness (GDW) in 100-year scale show that the northern region has entered an arid period, and the southern, a humid period. At decade scale, the D-value of annual average air temperature over Southern Shaanxi (Hanjiang Valley) and Central Shaanxi Plain (Guanzhong Plain) has narrowed, i.e. the former with slight change and the latter with rapid increase in temperature. Both regions are arid with decease in precipitation D-value, namely, the plain becomes warmer while the south drier. Qinling Mountains play a predominant role in the climatic dividing. The runoff coefficient (RC) of Weihe River decreases synchronously with that of Hanjiang River due to climate warming . The RC of Weihe dropped from 0.2 in the 1950s to less then 0.1 in the 1990s.Weihe valley (Guanzhong Plain) is practically an arid area as a result of the shortage of water .The successive 0.5 and 1.0℃ temperature anomaly over China marks, perhaps, the important transition period in which the environment becomes more vulnerable than before .The study shows the obvious trend of environmental aridity, which is of help to the understanding of regional response to the global climate change.

Varying soil loss resulting from different land use leads to problems of soil coarsening to different degrees in Beijing hilly area. In this paper, the data of conventional tillage plot, the fallow plot and the wasteland plot at Miyun county, Beijing were used. The topsoil samples and profile samples were taken from the upper, middle and down slopes of the plots. The soil samples were sieved. Then the rock fragment samples, whose diameter is over 2 mmeach, were weighted by means of sieving. The percentage of rock fragments in the samples was calculated. The results show that thepercentageof rock fragments in fallow plot is the highest and the percentageof rock fragments in wasteland is the smallest. Provided the percentage of rock fragments in the samples of wasteland was known at a normal value, and the soil textureindex was expressed with the ratio of the percentageofrock fragments for other land use to the one in wasteland, then the indexes of fallow land, conventional tillage plot and wasteland are 2.96, 2.07 and 1, respectively. The characteristic of soil coarsening in section varies with different land use purposes.The section at wasteland is free from soil coarsening, while the sections at fallow plot and conventional tillage plot experience apparent soil coarsening. The results can be applied for land use planing and soil degradation evaluation.

Digital Earth can be understood as digitized reoresentation and the recognition for real earth and related, geo phenomena. Digital Earth consists of spatial information with different levels and application models with different objectives. It includes the establishment of base and thematic digital maps with global, national, regional and urban scales, and satellite image data with different resolution and various geo informations such as population, economy, society and their application systems. Geo informatic TuPu, as graphic representation of spatio temporal change of geo information, is an effective tool for the application of Digital Earth. “Tu”, in Chinese word, includes graphics, maps and images. The Chinese word “Pu” means the well regulated sequence arrangement of the congener things, such as spectrum, chromatogram. “TuPu” involves the characteristics of “Tu” and “Pu” at the same time. Geo information TuPu can not only reflect spatial distribution characteristics of geo phenomena and regional differences between them, but also reveal the deeper level rules related to the cause of formation, the process of evolution and morphology. Having the aid of computer visualization and Virtual Reality technology, TuPu can dynamically and muti dimensionally reveal the spatial temporal distribution and evolvement laws of all kinds of geo phenomena. In this paper, the technological system of Digital Earth and its significance, and the concept of Geo informatic TuPu are discussed firstly, then, the model of Geo informatic TuPu transmission is presented. On the basis of the above mentioned researches, the relationship between Digital Earth and Geo informatic TuPu is discussed. It reaches to the conclusion that the development of Digital Earth will provide with abundant information resources and strong technological support for Geo informatic TuPu researches, and the enforcement of Digital Earth strategy will supply Geo informatic TuPu. Geo informatic TuPu will be an improtant means of the use of Digital Earth, and its researches will greatly broaden the domain of the application and the research of Digital Earth.

Comprehensive survey and analysis of the headwaters of the Mekong River by use of GPS, GIS and SRS show that the source of the Mekong River is the Zha'aqu River which starts from the terminal of a small glacier on the Guozongmucha Mountain in Zaduo County, Qinghai Province The altitude of the source is 5244m, lying between 94°41′44″E and 33°42′31″N The Mekong River flows through six Asian countries and ranks as the 12 th largest river in the world From the source to its first convergence of bigger tributaries of Zha'aqu River and Zha'naqu River, Ganasongduo ( 94°36′40″E and 33°12′33″N ), the Zha' aqu River has a length of 101.1km, a drainage area of 2634 0km²and a discharge of 117.4m3 /s which was measured on July 12, 1999 From Zhanahuohuozhudi ( 93°52.926′E and 33°16.534′N ) to Ganasongduo, the Zha'naqu River has a length of 93 0km, a drainange area of 1999 3km²and a discharge of 32.3m³/s which was measured on July 12, 1999 At the joint ( Ganasongduo ), the current direction of the Zha'naqu River is from west to east and the Zha'aqu River is from north to south After jointing, the river is called Zaqu River and It's current direction is nearly from north to south The run of the Zha'aqu River is similar to that of the Zaqu From Ganasongduo to Changdu in Tibet Autonomous Region, the Zaqu River is 518 km in length Down from Changdu to the outlet of the river inside China, the river is called Lancangjiang River, which has a drainage area of 167487km², a length of 2161km and a mean annual discharge of 2180m³/s

In regional economic development, the profit-making enterprise is the microcosmic basis. So it is full of vigor in market-economy. The author thinks that the coordinated process of regional economy is actually the operational process of regional economy of the profit-making enterprises. It means that only through the circulation of resources,fund and commodities among these enterprises, can the regional economy achieve coordination. On the basis of economic location and lots of statistical data, this paper researches the models and ways about enterprises spatial effect, which is the microcosmic mechanism of the regional economic coordination, for the purpose of making regional economy achieve marketablization, and regional economic coordinated and healthy development. In this paper the authors analyzed the leading industries in the cities of Wuhan,Shiyan and Xiangfan and came to the conclusion:(1)from Shiyan to Huangshi the metallurgical and engineering industries take the lead and are stretching to Henan and Jiangxi provinces;(2)Shashi and Xiangfan are the cores of textile industry, they will become stronger and stronger and will eventually unite as one.

In situ observations of soil moisture are invaluable means in developing land surface parameterization and studying pattern of climate change. However, the existing observations have been done only at point scale. Hence as to how to get regional soil moisture is of especially important. In this paper, geostatistical method (Kriging) is used to estimate soil moisture unknown at site A based on known soil moisture data around A. The data set of soil humidity in the top 1 m of 102 agrometeorological stations over China in 1987 is used for the estimation. In order to test how well the method works, we estimate one station's soil moisture as unknown by using other station's data. The observational data from that station is then taken as the true value. We gave the RMSE of Kriging interpolation method. and compared it with inverse distance square method The accuracy of the estimation is not high in terms of average relative error and standard deviation index For further analysis ,we took fperiod which had the maximal samples as an example.The average relative error of both methods was 0.26, the standard deviation of Kriging was 8.77 , the standard deviation of 5.17. The better results of the latter method was maybe due to itshomogenization over all the data with difference between the maximum and the minimum observed soil moisture being 42.85 that by geostatistical method being 31.25 and that by inverse interpolation method being 24.09. It is suggested that the combination of the two estimation methodsmay give better results. The inverse distance interpolation method is suitable for data with general variation characteristicswhile the geostatistical method is good for regional variable tendency. The average range calculated in this paper, around 500 km, is in agreement with the result of Entin et al. (2000) from 49 stations and 11 year records and Liu et al. (2001) with 99 stations with 3 year records.

The altitudinal zonation of natural landscape have distinct characteristics on the northern slope of the grand Taibai Mountains. The landforms consist of the higher district of the mountain all over which glaciers remain scattered, the middle district characterized by stone forest, and the lower district covered with loess. The mountain climate may be divided into four zonations: subfrigid zonation→frigid-temperate zonation→temperate zonation →warm-temperate zonation. The altitudinal vegetation zonations are : zonation of alpine shrubby meadow →alpine conifer zonation →birch zonation →zonation of mixed Form. plnus armandi, Quercus and deciduous broad-leaved forests →low mountain and hill dry deciduous broad-leaved forests and oriental arborvitae zonation. Influenced by those factors, the representative altitudinal zonations of the soils have been formed on the northern slope of the Taibai Mountains. But when pedogenetic classification was applied, there were many different classification results of the soil altitudinal zonations on the northern slope of the Taibai Mountains. Because the pedogenentic classification was based on the biologic and climatic conditions, and the soil forming processes, the central conceptions were emphasized but the boundaries of the conceptions were neglected in the pedogenetic classification. For convenience of international communication, the Chinese Soil Taxonomy was published in 1995. Then the characterizations and the factors of soil formation were investigated on the northern slope. According to the Chinese Soil Taxonomy (revised proposal), the result of the soil Taxonomy is obtained:Umb-Cryic Cambisols (>3 500m) →Mol-Cryic Cambisols (3 300～3 500m) →Acid-Udic Cambisols(2 500～3 300m) →Hap-Udic Luvisols (1 400～2 500m) →Hap-Ustic Luvisols (<1 400m). The result of the Taxonomy coincides basically with that of the pedogenetic classification and the boundaries roundly identify with each other. The results of two soil classification systems show that the Chinese pedogenetic classification is based on the pedogenic theory, and the Chinese Soil Taxonomy is guided by soil genesis principle. There are close relations between two classification systems. In addition, measurable diagnostic horizon and diagnostic characteristics are used to classify soils in the Chinese Soil Taxonomy, which make soil classification more quantitative and more objective, and soil classification standardized.

The driving forces and the changes of the tropical forest in Hainan Island of China were studied mainly by means of analyzing investigation data and forest survey materials, interpreting remote sensing data, using contour maps, and overlaying them with GIS, investigating the spatial variation survey and visitation during April of 1998 and May of 1999. The dynamic changes of tropical forest change as follows: 1) The area of tropical forest in Hainan Island changed obviously, which decreased from 1 200 000 hm² (1950) to 415 200 hm² (1979), and restored to 614 700 hm² by 1998.2) Since historical times, the changes can be divided into deceasing period (-1987) and increasing period (1987-). The former can be subdivided into three phases: resource decreased slowly (from Han Dynasty to 1933, annual average decrease of 984 hm²), resource decreased sharply (1933～1979, annual average decrease of 27 800 hm²) and resourcedecreased slowly (1979-1987); from1978 to 1998, the resource was restored steadily, annual average increase 20 300 hm². 3) Thespatial changes are mainly represented in the processof deforestation taking place from coastal plain and mesa to inland hill and basin, and finally to mountainous areain the middle of theisland. 4) Themain factors which affect the tropical forest are not the same in different phases. FromHan Dynasty to 1933,it is just due to aboriginal cultivation; from 1933to 1950, it is due to plundering cutting and destroying; and in the last 50 years, the ultimate causeis due to over fastincreasing of population and changes in policy and economy system.

The data of satellite remote sensing can provide real time information of the earth's surface accurately. Now the commercial satellites can provide the satellite images with the resolution between 10 meter and 1 meter. With those high spatial resolution images, shape features and texture features of the ground objects including large buildings of city, roads, rivers, lakes and other man made objects are very clear. With the characters of the high resolution satellite image, we will use the recognition of the type of water bodies as an example, begin with the extraction of the spectrum features of the ground objects from the satellite digital images, separate water bodies from background and recognize it through the classification of the image, implement the recombination of the pixels, then extract and describe the shape features of water bodies and implement the recognition of various water bodies on the partition of areas and the tracing of boundary. The experiments of the recognition of various types of water bodies on the satellite image prove this recognizing method is feasible with high spatial resolution satellite images.

Along with the changes of glbal climate and intensification of human interference capacity to nature, water cycle in catchment evolvement from unitary natural pattern to dual dynamic pattern made up of original natural water cycle and artificial water cycle, and intrinsic water resources status change greatly So it is very important to study water resources bearing capacity in dual water cycle pattern According to characteristics of water resources bearing capacity, this paper establishes imitate model with system dynamics theory The model consists of modules about water resources exploitation,industry,agriculture,population and environment, which are integrated with a group of dynamic equations such as level equation,rate equation, assistant equation and so on And then programme in DYNAMO language is worked out After inputting original data and various velocities of variables, one can get water resources bearing capacity at varying development schemes Finally by applying the model to study water resources bearing capacity in Guanzhong region of Shaanxi province where water resource is inadequate lack, water resources bearing capacity indexes at four different schemes are, obtained from that acquires the satisfaction scheme which can promote coordinated development of society,economy and environment In natural and manpower dual water cycle patterns, comparing system dynamics with other methods, the former is easier to get regional water resources bearing capacity of vary schemes, the calculation results are much more represented, and can factually simulate harmoneous development status among society,economy and environment It is thus innovative and maneuverable to study water resources bearing capacity with system dynamics

In this paper, we try to apply the economic model of economic growth and trade expansion (in the case of large country) to the economic analysis of regional economic difference in order to research the expansion course of regional economic difference At first, we introduce the economic model of economic growth and trade expansion (in the case of large country) briefly Secondly, we apply the economic model of economic growth and trade expansion (in the case of large country) to the regional economic analysis to set up the regional model of economic growth and trade expansion and use this model to research regional economic difference We find that the welfare of some regions begin to decrease correlatively due to economic growth and trade expansion in the regional labor division Thus we draw a conclusion that it is the term of trade that leads the regional economic difference to expand Thirdly, we inspect the conclusion with the figures of east and west of China Moreover we inspect the causal relationship between the term of trade and the regional economic difference through hypothesis testing of Granger causality and find out that there exists some causal relationship between the term of trade and the regional difference At last, we draw some conclusions as follows: (1) In the regional labor division, some regions are inevitably in a unfavorable state With economic growth and trade expansion, their terms of trade degenerate and welfare begin to decrease correlatively which led to expansion of regional economic difference (2) By inspection of the west and east of China, we find that there is causal relationship between the term of trade and regional economic difference (3) With the study of regional economic difference, we draw a conclusion that demand change is the main cause of degeneration of the term of trade Because the demand is in the base of industrial structure, so our study supports the conclusion that changes of industrial structure are the main impetus of regional economic growth

This paper reviews the process and researches on internal population migration in China since the economic reforms from 3aspects. They are the changes in migration process;the main reasons, choices and patterns of migration, migration and gender difference, migration and urbanization;and the participation and impression of migrants to city's economic and social life. The internal migration process in China since the economic reforms can be divided into 4 periods. The most important reason for migration is the difference of employment opportunities induced by regional economic disparities. The main migration pattern is through self organized network. Population migration has accelerated the process of urbanization. Migrants have become important part of urban labor market. But the temporary migrants in cities make them in weak status and difficult to dissolve into city life. This situation is unfavorable to the whole process of migration and urbanization in China. Large amount of positive researches give us a more and more clear knowledge to China's internal population migration, but most researches still remain within the frame of foreign country's theories. The author thinks that more researches in the following 4 fields are needed: the relation of population migration and the proceed of Hukou (registered residence)system reform, the relation of migration and the employment of urban citizens, the relation of migration and the industrial adjustment, the affection of temporary migrants to the comparing analysis of social and economic differences.

Agroforestry is a newly developed technique, which includes various fields and is suitable for developing countries. Recently, the contour hedgerow-crop system has become one of the major forms of agroforestry on slopeland in developing countries. It was proved intercropping between the contour hedgerows is favorable for controlling erosion, increasing soil fertility and gaining higher benefit of the slopeland by relatively low input. The primary objective of applying hedgerows is to control erosion and non-point pollution on slopeland. The distance between contour hedgerows mainly decides the effect of erosion control and the cultivable area in the hedgerows-crop systems. Therefore, the design of the distance is very important to applying the contour hedgerow techniques. The existing studies have not paid much attention to the hedgerow's control process for erosion and nutrient in the temperate zone and semiarid region. The present study quantitatively analyzes the rules of various erosion zones on a slope by using plenty of field observed data in hilly loess area of northwest Hebei Province, as well as large-scale artificial rainfall simulation data from sloping field. Taking contour hedgerow-crop system as an example, this paper discusses the major mechanism of soil erosion and nutrient change processes, the design of level spacial structure of typical agroforestry systems in hilly area of northwest Hebei. The results showed that the critical slope length is 10-15m on the condition of rainstorm, which can control the generation of rills and make the erosion amount decrease obviously. The study provides a theoretical basis for the hedgerow plant, and the hedgerow can control the erosion and nutrient loss through changing the erosion process on slopes and control thes generation of rill erosion. The study has a scientific value for the application of the hedgerow-crops agroforestiy system in the temperate zone and semiarid region.

With population growth and arable land decrease, the pressure of human activity on land resource is becoming greater. How to realize sustainable land use has become the focus of global society. Both the time scale and spatial scale have to be concerned when a sustainable land use planning was made. Normally, ecological suitability, economic feasibility and social acceptance of land use scenario have to be considered. Currently, most works concern more on theoretical aspect of sustainable land use rather than some practical approaches to realize sustainable land use. In this study, a procedure for carrying out such a planning is presented, based on results from a research project in a small catchment on the Loess Plateau. A land suitability evaluation for rainfed agriculture based on biophysical parameters, and a comparison between land suitability and current land use, were first carried out. Some potential land use scenarios, based on surveys on biophysical and socio-economic parameters in the catchment, and plans by the authorities, were proposed for further evaluation of their effects on soil erosion, economic feasibility and social acceptance. The results indicated that the following land use scenario was acceptable: all land with deep soil and slopes smaller than 15° is used for agriculture cropland, possibly combined with biological conservation measures, such as mulching combined with improved fallow, and all land with slopes steeper than 15° is used for other purposes (orchards and other cash trees, woodland, shrubland, grassland). A great reduction of on-farm income, however, would be induced on the short term by such a scenario. Local farmers will find it difficult to accept unless financial support from external sources is available. On the long term, the scenarios will be promising for both economic income improvement and soil erosion control since some production will be obtained from the conversion of cropland into orchards/cash trees (preferably on slopes 15～25°). Thus the land-use modification should be carried out gradually. On the short term (5 year), it is suggested that cropland on slopes steeper than 25° is returned to woodland/shrubland/grassland while also fruit trees are planted on slopes of 15～25°. Within 10 years, cropland with slopes steeper than 15° is suggested to be converted into orchard/woodland/shrubland/grassland.

From long term point of view, sediment delivery ratio of a drainage basin with a control degree reaching 70% can be reduced by around 50% in contrast to pre control conditions. The effect of erosion control is quite significant. In the management process, although delivery ratio drops considerably in comparison to pre control conditions, yet the previous retained sediment can still be carried, resulting in the situation of delivery ratio greater than 1 since erosive strength of rainstorm induced erosion is greater than project designed standard in a short spell following dike breach and scouring. In the loess plateau region, individual rainstorm event related delivery ratio under either pre or post control conditions in drainge system can be obtained by using runoff depth, and dynamic mechanism for changes of delivery ratio can be explained with shear force changes following fluctuations of runoff depth.