Current methods cannot meet the needs of evaluating landslide susceptibility because they cannot incorporate the nonlinear relations between landslide and the inducing factors as well as the different forms of relationships. A new approach integrating the expert knowledge and fuzzy logic is proposed in this paper to evaluate the landslide susceptibility. This method first encodes the knowledge from domain experts into four combinations of environmental factors: 1) the difference between slope gradient and the strata gradient as well as the difference between slope orientation and strata orientation, 2) slope gradient and lithology, 3) slope height and lithology, and 4) slope shape and lithology, and thus incorporates the relativity between factors into these combination models. Information on variables involved in these combinations is characterized using a set of GIS techniques. The susceptibility of a given location hence can be evaluated by evaluating each combination and overlaying the values from these four combinations. Some parameters in these models are determined by statistical analysis, and others are provided by landslide experts. The approach is applied to a section of the Three Gorges area from Yunyang to Wushan, and a susceptibility map is produced. The result shows that the computed susceptibility values are much higher over areas with landslides than areas without landslides. We conclude that our approach is capable of capturing the landslide susceptibility.
This paper focuses on the problems of urban torrent hazard in the recent years and reviews the current study status and future research work about assessment of urban torrent hazard. According to torrent - breeding environment, triggering factors, social and economic situation of flooded area, this research formed a GIS based technical methodological system, which is shown as following: collect data →establish database of spatial attribute →choose the system of assessed indexes→analyze forecasting estimation→torrent hazard assessment and risk zonation. Based on this, an integrated methodology for urban torrent risk assessment is approached. Procedure of the methodology for torrent hazard zonation in the flooded area, urban vulnerability analysis, loss evaluation and risk assessment, torrent hazard zonation on the alluvial fan are created via geomorhologic method and the numerical simulation method. Detailed land cover information was derived by using the high resolution satellite imagery and then we evaluated the vulnerability values on different land - use features. Based on a GIS statistical and analytical tool, urban torrent loss and risk for urban area is evaluated. These assessments can be used for torrent mitigation by identifying hazard areas, allowing for avoidance through zoning or other land use policy decision. In addition, residents who live in torrent areas need risk information for evacuation and flood control.
Soil respiration is an important part of global carbon cycle, which accounts for about 25% of the global carbon dioxide exchange. Estimating the contribution of soil organic material ( SOM- derived ) respiration, root respiration and rhizomicrobial respiration to total soil CO2 efflux and the carbon distribution between actual root respiration and rhizodeposits is crucial in determining the carbon and energy balance of plant and soil. Up to date a large amount of the researches have been done on partitioning total soil respiration into autotrophic and heterotrphic components and great progress has been achieved. But it is still very difficult to discriminate between the CO2 directly derived from actual root respiration and that derived from mineralization of rhizodeposits, and this has presented one of the greatest challenges to quantifying rhizosphere C- flow. Several methods have been suggested to separate SOM- derived respiration and root- derived respiration (including actual root respiration and rhizomicrobial respiration): (1) integration of component method, (2) trenching method, (3) root- excising method, (4) gap formation method, (5) root mass extrapolation method, and (6) isotope method. Also there are several methods to separate actual root respiration and rhizomicrobial respiraton: (1) isotope dilution method, (2) model rhizodeposition method, (3) 14CO2 dynamics method, (4) exudate elution method, (5) 13C of CO2 and microbial biomass and (6) combination of some no- isotopic methods. This review has described the basic principles and assumptions of these methods and compared the results obtained in the original research papers.
At the beginning of the new century, the issue of ecological security has been put on the agenda of the government in many countries owing to increasingly deteriorating environment of the world. Because regional ecological security serves as the basis of sustainable regional and national development, it comes to be the focus of ecological security. The aim of this study was to develop a comprehensive evaluation system for regional ecological security. Wanquan County of Hebei Province, located in a transitional zone between the farming and pastoral regions, was taken as a case study area. It serves as one of major channels of sandstorm transportation from Inner Mongolia to Beijing. After processing of basic data and in accordance with the principle that evaluating indicators should be dynamic, principal and operable,3 types of evaluating indicators, including vegetation changes, LUCC and soil erosion, were selected. By the comprehensive index method, the dynamic evaluation model was built with the three types of indices based on ecological degradation, and their weights were worked out by introducing least squares solution. And then, the evaluation image for ecological security was generated in ArcGIS9.0/Spatial Analyst module and the model was realized. The final results show that the situation was better in the river area and insecure areas distributed in north part and middle part mainly. An average score of 2.3 in a 4- grade range would not only tell the ecological condition for the entire study area, but also remind the local government to pay more attention to ecology protection. It was proved that dynamic evaluation indicators were superior to static ones for ecological security evaluation, and the least squares solution was a practical and scientific method to balance the weights for evaluation indicators. In addition, the evaluation system was proved to be qualified and synthetically corrected also by applying it to other counties around Beijing.
Based on the analysis on the difficulty of wetland boundary identification and its causes, and having reviewed the wetland boundary indicators and their criteria selected at present, the paper suggested that, under the condition that the mechanism of wetland formation process has not been fully understood, all of the wetland boundaries based on hydrology and vegetation criteria are to some extent arbitrary boundaries. Wetland boundaries based on arbitrary criteria are not wetland's natural boundaries, because the natural boundaries of any complex can only be cognized, not be "man- prescribed". Even if there is no controversy on the criteria, it is usually impractical to identify wetland boundaries in the field accurately, because it takes repeated visits over a lengthy period of time (several years), and both seasonal conditions and then recent weather conditions should be considered when these indicators are applied. Wetland boundaries based on instantaneity indicators are unrepeatable and controversial. Aiming to resolve the problems on wetland boundary delineation, the paper analyzed the principles of the System Theory and physical geography related to wetland boundary delineation, and put forward a new method for wetland upper boundary identification. The method suggested that, under the condition that the mechanism of wetland formation processes has not been fully understood, "black box"method of System Theory can be used to identify wetland boundaries scientifically; when it is difficult to identify wetland boundary based on the characteristics of wetlands itself, if the boundaries of aquatic and terrestrial systems can be identified, they can be regarded as the wetland' s lower and upper boundaries; the lower limit of rooted plants is chosen as the indicator for delineating wetland lower boundary, and the thinning- out point of the diagnostic horizon of zonal soil is chosen as the indicator for wetland's upper boundary, because the thinning- out point is a kind of critical point, and it can factually reflect the long- term interaction result of all environmental elements. The scientificity and feasibility of the method was also analyzed. The characteristics of the diagnostic horizon, which is less responsive to short - term change than wetland vegetation and hydrology, make sure that the delineating result is repeatable, and that the controversy can be avoided.
In recent years, with more and more officials and professionals paying attention to the problems such as soil erosion and water loss, the exquisite contradiction between water supply and demand, whether soil and water conservation measures on upper regions would have effect on the amount of water resources of the lower reaches is a scientific issue to be discussed and probed into urgently. Primary achievements of effects of individual soil and water conservation measures on water resources as well as benefits of runoff reduction of watershed management in China have been reviewed and analyzed synthetically on the runoff plots scale and whole watershed scale respectively, and the benefits of runoff reduction of some large watershed have been analyzed and compared with each other . Some existing problems in this research field at present have been expounded and prospect is put forward at last.
Terrestrial carbon cycle and nitrogen cycle are closely coupled. Some factors, such as temperature, water and CO2 concentration, were more considered in the previous carbon researches than the nitrogen because of the complexity of nitrogen cycle, but this situation has changed in recent years. Nitrogen has great effects on the plant photosynthesis, organic matter decomposition, carbon allocation and the responses of ecosystem when the atmospheric CO2 concentration increases. There are generally three types of carbon models to consider nitrogen limitation on carbon assimilation: (1) static models: these type models usually use a constant soil fertility index or leaf nitrogen concentration and are fit for a site or district where the nitrogen variability can be neglected; (2) soil nitrogen limitation models: these models can maintain stable nitrogen budgets and dynamic soil nitrogen can turn the potential NPP to actual NPP; (3) leaf nitrogen limitation models: such models are similar to soil nitrogen limitation but feature a further dynamic leaf- level nitrogen regulation of NPP. The common approach uses relative leaf nitrogen concentration to scale down proportionally either the maximum Rubisco or the NPP. Although the three type models all consider the nitrogen effects on carbon cycle, they may produce great uncertainty in carbon research because of the partly understanding of the interaction between carbon and nitrogen. Future studies should focus on both the experiment and observation about the nitrogen feedbacks on carbon cycle and the development of integrated dynamic ecosystem models that can describe the interaction of carbon and nitrogen cycle, contributing to decreasing the uncertainty in the carbon research.
Modeling is a key method in the study of climate- vegetation, which is an important content in the field of global change researches. As a huge geographical unit, the Tibetan Plateau has strong effects on Chinese and East Asian climate because of its unique location and higher elevation. Because of special environment, the biomes on the Tibetan Plateau have many distinguishing characteristics that are not shown by some global models. The above- mentioned characteristics and less human disturbance make it an important area for study on climate- vegetation. This paper reviews five major types of climate- vegetation models that have been widely used to simulate response of vegetation to climate change and points out its advantage and disadvantage. Combining some related researches on the Tibetan Plateau, the paper summarizes the progress of climate- vegetation modeling from two aspects of vegetation distribution and vegetation net primary productivity, and finds modeling is a very important way for climate- vegetation researches. Nevertheless, in fact, climate- vegetation modeling is lagged behind other areas. So the crux of works in future is to master the crucial theories of climate- vegetation mutual reaction, then develop pertinent models with characteristics of the Tibetan Plateau.
Accurate estimation of surface evaporatranspiration (ET) is important in the study of global climatic change, scientific management of water resources. In this paper, the evapotranspiration from 1981 to 2003 in Wushen County, located in the Mu Us Sandland, was estimated by using Advection - Aridity Model based on the complementary relationship hypothesis with 1km resolution reflectance data of NOAA/AVHRR and MODIS and meteorology data. The temporal and spatial distribution of ET was analyzed. The results showed: (1) The annual average of ET of Wushen County is 252 mm. Spatially, it increases from northwest to southeast. The multiyear relative variation of ET in Wushen County is from 10% to 24%, larger in northwestern and southeastern parts and smaller in eastern and southern places. Seen from the yearly spatial distribution of the ET, there is the same trend that ET increases from west to east. (2) Ordered in land cover and land use in 2002, ET decreases in following sequence: water body, crop field, grassland, shrub, forestland and sand land. (3) Interannual change of ET in Wushen County is large while the maximum value is up to 300mm and the minimum value is only 200 mm. The monthly distribution of ET takes a 'bell'shape, with peak in about July to September.
The climate is changing due to higher concentrations of greenhouse gases. If concentrations continue to increase, climate change will be more severe in this century based on climate models project. And it will have significant impacts on many human sectors, especially on agriculture. Agriculture is the foundation of society, especially for China with large population. Wheat is the second most important crop in China. Therefore, it is necessary to assess the impacts of climate change on wheat in China. In order to predict the future risk of climate change on Chinese wheat production, firstly, fifteen- year ECMWF re- analysis data (1979~1993) is used as quasi- observed boundary conditions to drive regional climate modeling system- PRECIS, then the dataset is employed to test the effects of feeding CERES-Wheat model with RCM daily outputs directly via comparing the simulated results and the station observation. Based on the above validation, two wheat stations (Ding Xi and He Fei) were selected to assess the possible changes of future two production under IPCC SRES A2 & B2 scenarios. The rained and irrigated wheat production without and with CO2 fertilization effect, were simulated respectively. It is shown that: regardless of A2 or B2 scenarios, the future climatic change will increase wheat yield both in Dingxi and Hefei to some extent, but the range increased differs greatly. The yield increasing effect of A2 scenario will be generally greater than B2 scenario, the irrigated wheat will benefit more than rainfed wheat, the winter wheat (Hefei ) has larger increasing degree than spring wheat (Dingxi ). With the directly fertilizer effect of CO2, all the treat will increase by a large margin.
This paper uses economic geography analytical methods and basic theories of the traffic geography, regards Liaoning Province and affiliated 14 cities as the research object, analyzes in depth the characteristics of formation, growth, distribution and exchange of the highway freight transportation in Liaoning Province. "Hub- and- Spoke"network originated from airplane transportation. In this paper it is applied to road freight transportation network, and this is a creation. "Hub- and- Spoke"network has already become the basic mode of highway freight transportation network in provincial region, and it embodies "Dual- nuclei" structure characteristic at the same time. This text divides highway freight transportation network of Liaoning Province into two systems of Shenyang- Dalian and west of Liaoning. In conclusion, the industrialization and transportation linkage of Liaoning Province enters middle and later periods, and the regional concentrations index of the traffic volume of the goods is high relatively. There are following characteristic in the highway freight transportation spatial linkage in the provincial region: there is one or several central cities, the volume of goods transported is decided by the nature of the city to a great extent, goods transportation is not closely related to the distance, and coastal port exerts a tremendous influence on the spatial linkage and so on.
The rapid increase in economy and high- speed development in information industry have made Internet in China grow quickly. Meanwhile, the social informationization step has accelerated and regional information disparities have emerged. Combining the number of domains in each province with maps, this paper discusses these disparities in China spatially and temporally. Meanwhile, we improve some methods of correlation analysis, Lorenz Curve and location quotient et al., which are different to the traditional economic ones such as GDP. The conclusions are as the following: (1) The Internet development in China declines gradually from Eastern China to Western China. (2) The gap between high level provinces and low level ones was big. For example, in 2001, domains in Beijing were 442 times as much as those in Qinghai province. (3) Although the absolute disparities between Eastern China and Central China as well as Western China were widened from 1999 to 2005, the comparative disparities in each province were constant by and large. (4) This paper classified provinces into five categories using location quotient, which represents the difference with the average level. The classification distribution showed that the Internet development in Eastern China was increasing, in contrast to the stagnation in Central China and Western China. So, the development in Central China and Western China should be paid much attention to by the government. (5) The spatial distribution of domains was consistent with that of provincial GDP, but not accordant absolutely.
Urban- rural interaction development refers to the two- way flowing and optimial allocation of capital, labor, material, information and other socio- economic factors in urban- rural space. Urban- rural interaction development has changed one- way flowing pattern of urban- rural socio- economic factors under urban- rural segregation system, promoting urban- rural common development and overall optimization of regional spatial structure. Meanwhile, in the cross- research field of urban geography and rural geography, urban- rural interaction development will also help to widen research system of geography and provide new research framework for constituting a new round of regional planning and urban- rural planning. Therefore, in the process of building new socialism rural areas and harmonious society, it is necessary to carry out theoretic and practical study on urban- rural interaction development. This article summarized the domestic and foreign research achievements on connotation, mechanism, pattern and way of urban- rural interaction development during the last 15 years, and pointed out that the current researches might mostly favor qualitative and static aspects, while lacking quantitative and dynamic analysis from perspective of the different spatio- temporal dimensions. Therefore, there are three principal issues urgently needed to be solved in the future: (1) Strengthening the research on basic principles of urban- rural interaction development. Spatial economics theory, system science theory and coordination symbiotic theory may be used to analyze the form, content, structure, function and mechanism of urban- rural interaction development. (2) Strengthening the research on mechanism and rule of spatio - temporal evolvement of urban - rural interaction development. Some mathematical methods may be used: firstly, the Two- stage Nested Theil Decomposition method and Exploring Spatial Data Analysis method may be used to reveal the spatial difference of urban- rural interaction development. Secondly, Wavelet Analysis method may be used to reveal temporal variation characteristic of urban- rural interaction development. Thirdly, Grey Association Analysis method and Granger Cause and Effect Analysis method may be used to reveal the relations between urban- rural interaction development and their driving factors. (3) Strengthening the research on the pattern and optimization countermeasure of urban- rural interaction development in different types of regions. Questionnaire and interview methods may be used.
By Aug. 2003, there were more than 2 million motor cars, including 1.3 million owned by privates. As population expand incomes increase, and car prices go down, more cars will be seen in streets of Beijing. Beijing's traffic congestion causes many social and natural problems, such as air pollution and deaths in traffic. We recommend using the externality theory of environmental economics to understand the externalities of car transportation. The crux of Beijing's traffic congestion is the market failure caused by its externalities. Because of the group characteristic of the car transportation, the handling of its externalities should be relied on government solutions. By looking into other cities'traffic measures, such as London of UK, Singapore and Nagoya of Japan, we recommend using the combination of force control and economic incentive to reinforce the management of Beijing's traffic, so as to control the total amount of cars, to limit too many cars to go into the center of the city in rush hours and to encourage the citizens to use the mass transportations. Limited certificate of car ownership, congestion charging, and encourgement system for using mass traffic tools might be considered to apply in Beijing.
