A remarkable empirical regularity is that the city size distribution in many countries is well approximated to a Pareto distribution. This claim is so widely accepted that it has gained the status of a law, Zipf’s Law, or a rule, the Rank-size Rule. It has also inspired extensive researches mainly in the fields of economic geography and regional science. The urbanization process has mainly taken place since 1978 with significant processes of industrialization and economic growth in China. Many researchers have studied the characteristics of city scale distribution in different regions according to Ordinary Least Squares (OLS). The spatial econometric analysis of urban system is still scarce. This article adopts spatial econometric models to analyze the Rank-size Rule and evolution mechanisms of urban system in China’s middle area through population data of prefectural-level cities from 1985 to 2009. Firstly, cross-sectional distribution of urban population is analyzed by means of nonparametric estimations of density functions. Evolution of the shape of urabn population cross-sectional distribution shows the existence of convergence trends. Secondly, the linear regression equation is estimated by OLS. Then spatial autoregressive model and spatial error model are estimated. The results show that the estimation over time of the q parameter displays an increasing trend from 1985-1990, then decrease until 1995, from which it starts to augment. Zipf’s exponent estimated by spatial lag model is smaller than OLS. It indicates that the size distribution of urban system is more convergent because of significant spatial dependence between cities. Thirdly, we explore the mechnism between the spatial dependence and city size distribution. Spatial interaction caused by the agglemation of production factors, industrial adjustment and innovation diffusion provides the basis of spatial dependence. It affects the evolution of urban system and makes urban size distribution more convergent. Finally, the article concludes with a summary of key findings and puts forward some recommendations.
A remarkable empirical regularity is that the city size distribution in many countries is well approximated to a Pareto distribution. This claim is so widely accepted that it has gained the status of a law, Zipf’s Law, or a rule, the Rank-size Rule. It has also inspired extensive researches mainly in the fields of economic geography and regional science. The urbanization process has mainly taken place since 1978 with significant processes of industrialization and economic growth in China. Many researchers have studied the characteristics of city scale distribution in different regions according to Ordinary Least Squares (OLS). The spatial econometric analysis of urban system is still scarce. This article adopts spatial econometric models to analyze the Rank-size Rule and evolution mechanisms of urban system in China’s middle area through population data of prefectural-level cities from 1985 to 2009. Firstly, cross-sectional distribution of urban population is analyzed by means of nonparametric estimations of density functions. Evolution of the shape of urabn population cross-sectional distribution shows the existence of convergence trends. Secondly, the linear regression equation is estimated by OLS. Then spatial autoregressive model and spatial error model are estimated. The results show that the estimation over time of the q parameter displays an increasing trend from 1985-1990, then decrease until 1995, from which it starts to augment. Zipf’s exponent estimated by spatial lag model is smaller than OLS. It indicates that the size distribution of urban system is more convergent because of significant spatial dependence between cities. Thirdly, we explore the mechnism between the spatial dependence and city size distribution. Spatial interaction caused by the agglemation of production factors, industrial adjustment and innovation diffusion provides the basis of spatial dependence. It affects the evolution of urban system and makes urban size distribution more convergent. Finally, the article concludes with a summary of key findings and puts forward some recommendations.
Regional specialization and division degree of manufacturing industries are measured by Krugman index and location quotient index in Central China in 2000, 2004 and 2008. And then, the situation and evolution of cooper-competition relationship among six provinces in Central China are discussed by the cooper-competition model composed of Markov chains. Results show that the manufacturing industries specialization degree among provinces in Central China had been improving, but the disparity of inter-provincial division level was quite remarkable, especially the division degree of manufacturing industries were higher between Shanxi and other provinces than others which is closely related to the energy resources advantages and the manufacturing industries structure. Regional specialization range among provinces which possess circumjacent geographical position or similar resources advantages was lower than the not. Cooper-competition analysis shows that the complementary cooperation relationships between Shanxi and other central provinces were strongest, while competitive relationship among other provinces and the polarization trend of cooper-comptition were more and more prominent. Markov chains analysis shows that the transformation of cooper-competition relationship only occurred between the adjacent types. During the process of cooper-competition relationship transformation, the probability of shifts to powerful complementary cooperation type or powerful competing type was higher that others and the polarization of cooper-competition relationship among provinces in Central China was becoming remarkable gradually. From this, it can be seen that under the Central China′s emerging strategy background, harmony and ordered regional specialization and division pattern should be constructed through taking the development advantages of every province, letting down the bars of administrative boundaries, and breaking the market protection and reducing the cost of transaction. The regional linkage and cooperation should be strengthened and the regional cooperation mechanisms should be established, including governments, enterprises and other organizations in order to achieve comprehensive linked and integrative development in Central China.
With the rapid spread and expansion of big cities, the increasing of traffic congestion is one of the main problems in the process of urban development, which becomes a hot research topic. With the time geography method, this article discusses the formation mechanism of traffic congestion under the perspective of spatio-temporal agglomeration of residents’ daily activities with a case of Guangzhou. The results show that, motile co-existence is the root cause of traffic congestion, while the agglomeration of spatio-temporal paths cause motile co-existence. Guangzhou residents’ activities are conditioned by space and time constraints, which forms the motile co-existence. The urban space and road structure enhance the agglomeration of spatio-temporal paths, so as to form the coexistence of daily activities and traffic congestion. Therefore, path cluster is the fundamental cause of traffic congestion under the constraints of time and space. In conclusion, residents’ daily activities are constrained by time and space, when the constraint reaches to a certain degree, the spatio-temporal agglomeration and motile co-existence will be produced, and finally forms traffic congestion. Good traffic management can only make traffic congestion tend to get better but cannot solve the problem of traffic congestion in essence. The structure of urban space, traffic lines, traffic control, and the situation of transportation supply and demand in some degree affect traffic congestion through motile co-existence. With the situation of transportation supply and demand at a roughly balanced level, the basic measures to solve the problem of traffic congestion lies in resolving the agglomeration of residents’ daily activities.
The research on ecological security of land use is the core of IGBP and IHDP, which can provide a lot of guidances on the regional ecological construction and sustainable development. Based on RS and GIS technology, taking typical Jining City in Nansi Lake watershed as the study area, the paper analyzed land use change in Jining City from 1987 to 2008, and then an evaluation index system was established on basis of “Hazard-State-Immune” model. AHP and entropy methods were used for determining index weights, finally improved TOPSIS method was used to evaluate ecological security on 100 m×100 m grid scale in the year of 1987, 2000 and 2008. The results of the study were as follows: 1） the change of land use in study area from 1987 to 2008 was great, and had typical regional characteristics. The areas of farmland, woodland, grassland and unused land kept decreasing, construction land expanded largely, water area first decreased and then increased. 2） In the past 20 years, ecological security in study area changed from deterioration to improvement, experiencing V-shaped process, and the main reasons of improvement since 2000 were implementation of the South-to-North Water Transfer Project as well as enhancement of ecological construction. 3） The spatial difference of land ecological security in research area was obvious, the best places were located in the eastern hilly area and Nansi Lake, the worst places were located in the middle area, and the remaining areas were in a warning state.This study revealed temporal evolution and spatial distribution of the land use and ecological security in Jining city, which played a conducting and reference role in ecological construction, regional sustainable development, and improving water quality standards of the East Route of the South-to-North Water Transfer Project.
：It is significant to quantitatively analyze the direct and indirect effects of driving factors on urban land use structure for macro-control and optimization of urban land use. Method of path analysis was employed. The results indicate: 1) Direct effect of population growth to the proportion of residential is 0.446, the indirect effects are -0.189, 0.221, -0.042 through economic development,industrial structure change and transport infrastructure development;the indirect effects of economic development,industrial structure change are 0.420, 0.309 through population growth. 2) The direct effects of industrial structure change and economic development to the proportion of industrial are -1.357, 1.236, respectively; the direct effects to the proportion of public service land are 1.387, -1.100;the indirect of population growth to the proportion of industrial land and public service land are 1.163, -1.036 through economic development, but the effect direction is opposite. 3)economic development ,transport infrastructure development and industrial structure change are the main driving factors of the proportion the green space; the indirect (0.451) is bigger than the indirect effect (-0.117) of population growth to the proportion of green space through economic development. 4) economic development,industrial structure change, population growth and their coupling effect are the main driving factors of urban land use structure.
The article selects 3 large index systems such as competitiveness of resources product, market service as well as tourism security, and uses entropy method to give weight to the 3 big index systems so as to measure urban tourism competitive potential of the Changjiang River Delta horizontally. Combined with SSM model, this article calculates longitudinally the structure deviation component and competitiveness deviation component of urban tourism competitive potential index factors from 1998 to 2008. At the same time, the structure effect and the competitiveness effect of index factors are evaluated on the basis of longitudinal calculation. The results show that there are significant differences in the temporal patterns of urban tourism competitive potential of the Changjiang River Delta. The urban tourism competitive potentials of 4 central cities including Shanghai, Nanjing, Hangzhou and Suzhou are higher, which form the spatial pattern of 4 culminations. Moreover, the difference of urban tourism competitive potential displays the expanding trend. However, it occurs that there is unreasonable situation of the structure of index factors, which does not match entirely with the corresponding tourism competitive potential. Specifically, the whole competitiveness of market, service, traffic carrying capacity and economic development support of Shanghai is very strong. On one hand, the basis of image competitiveness is better while the competitive potential has the decreasing trend. On the other hand, the basis of resources competitiveness is better while the state begins to decline. The significant characteristics of Hangzhou City are that the competitiveness of image and product has the good development, which has the better basis and the large competitive potential. For Nanjing, its competitiveness of market, resources and product has the better basis and its status advances distinctively while other indexes appear the declining trend. The competitiveness of image and service of Suzhou City develops rapidly and has the prominent advantageous position. Therefore, through the two clear contrasts between the horizontal aspects and the longitudinal aspects, the weaknesses and defects of the different urban tourism competitive potential indexes are reflected and the performance of the different urban tourism competitive potential is shown objectively and accurately. As a result, the article provides the quantitative basis and the theoretical reference for advancing the different urban tourism competitive potential of the Changjiang River Delta.
With the degeneration of environment and acceleration of urbanization, human environment has attracted great attention worldwide. As one of the key factors, the relief degree of land surface is an important indicator for natural evaluation, and it also has high accuracy and practical application in small scale residential environmental evaluation. Based on lattice digital elevation model of scale 1∶25 0000 in Guangzhong-Tianshui economic region, using the window analysis and spatial analysis model of ARCGIS software, this article extracts the relief degree of land surface and population distribution in Guanzhong-Tianshui economic region. From the characteristics of proportion, spatial distribution and height, it also systematically analyzes the discipline of the relief degree of land surface and its relationship with the distribution of population in Guanzhong-Tianshui economic region. The study has shown that: 1) The relief degree of land surface in Guanzhong-Tianshui economic region is dominated by middle and low value, and its topographic area is less than 2.4 occupying 96.66% of the total area, and the average proportion occupying 32.4% of the whole area. The higher is the relief degree of land surface, the lower is the proportion of plains, and vice versa; 2) The relief degree of land surface in Guanzhong-Tianshui economic region presents such spatial patterns that the south and north are higher and the middle is lower, and there is the maximum value in Taibai Country in Baoji City and the minimum value in Guanzhong plains. The variation is not apparent on the longitude, and the degree of latitude increases after the first drop no matter from South to North or from North to South;3)As the altitude increased, the degree presents a rising trend but has not much change; 4) The relief degree of land surface has a strong impact on the regional distribution, nearly 90% residents in Guanzhong-Tianshui economic region lived in the area where less than 1.5 degree, the curved fitting of population density and topographic is very high; 5)The relational area of topographic and population distribution have significant difference, the topographic has obvious relation with population distribution, but the relationship of the topographic is smaller in four countries in Shangluo and Tianshui cities. To sum up, the relief degree of land surface can better reflect the topographic feature and reveal its regularities of space in Guanzhong-Tianshui economic region. Empirical research shows that, as one of the key factors, the relief degree of land surface is an important indicator for natural evaluation; it also has high accuracy and practical application in small scale residential environmental evaluation. In summary, the RDLS model established in this paper can not only reflect the natural environment suitability for human settlements in Guanzhong-Tianshui economic region, but also can illustrate the spatial distribution rules of it very well.
The Ellison-Glaeser (EG) index and the CR5 index were used to give a dynamic calculation and analysis of the industrial agglomeration level of China in the article based on the data of five branches of China′s mineral resources industry, which conclued the coal industry, oil and gas industry, non-metal industry, ferrous metal industry and non-ferrous metal industry from 2000 to 2009. The results showed that during 2001 to 2009, the mineral resources industry on the whole had developed to a relatively high level but at a relatively slow speed. The EG index of the four branches of the mineral resources industry was calculated as above 0.05 in 2009 except for that of the non-metal mineral industry; the five branches′ CR5 index presented an apparent agglomeration, which held at a level of 0.6 in most conditions. The oil and gas industry had the highest average value of 0.657, and the lowest was the non-metal mineral industry, which was only 0.512. On the other hand, from an industrial perspective, the calculation results of the EG index revealed great differences in agglomeration level and uneven developments among the five mineral resources branches. The branch which was heading for the top position of the EG index was the ferrous metal industry with an average value of 0.102 , which was five times as that of the non-metal industry. The coal industry came in at second and the nonferrous metal industry and oil and gas industry were at No.3 and No.4. The last position was held by the non-metal industry with an average value of only 0.028, which was the only mineral resources industry that did not present a high agglomeration level. In addition, there were some differences in the variable range of agglomeration levels among the five mineral resources industries. In contrast, the oil and gas industry had the maximal increase slope of 85.17%, while the non-metal mineral industry′s development was comparatively slow, which had presented an evident decline since 2008. The slow or negative increase slope would make high agglomeration levels hard to sustain. However, the CR5 index showed that the difference among the five branches of the mineral resources industry was relatively small. All five industries presented relatively low or negative increase amplitude; the coal industry was the biggest among the industries at only 4.41%. The reason being that the non-metal mineral enterprises of the first five ones in turnover, enjoyed a geographical agglomeration resulting in the non-metal mineral industry showing a high agglomeration level. This narrowed the differences of agglomeration levels between this and the other branches.
Palaeoflood hydrological studies were carried out in the upper reaches of the Hanjiang River. Palaeoflood slackwater deposit was found at the JJTZ site in the Baihe reach in the bedrock gorges. Analysis of the grain-size distribution indicates that these SWD consist of sandy silt, sourced from the suspended sediment load of the floodwater. Stratigraphic correlation with the chronological framework established in the Weihe River basin OSL dating show that these extreme floods occurred at the turn from middle to late Holocene, about 3200-2800 a B.P. at the end of the mid-Holocene Climatic Optimum. The reconstructed peak discharges of the palaeoflood range from 40 180 m3/s to 49 170 m3/s, which are much larger than the gauged largest floods. These results were further tested and proved to be reliable with reconstruction of the modern floods at the same reach with the same method. This research is of great importance in hydrological engineering and flood mitigation. And it is also very important in establishment of the relationships between extreme flood events and global climate change.
Depth hoar (DH) under different shading conditions in seasonal snow cover was studied in Tianshan Station Snow Cover and Avalanche Research Station in the winter of 2009-2010. Optical stereo microscope and the portable equipment Snow Fork were used to observe the grain size and shapes as well as water content and density of DH in the open ground (0 % shaded), canopy edge (50 % shaded) and canopied zone(90 % shaded). Results showed that: 1) DH growth primarily depends on temperature, and secondarily on temperature gradient. Temperature condition, caused by snow thickness depends on the snow accumulation and solar radiation, is the fundamental reason of DH’s differences under different shading conditions. 2) Both the snow depth and DH thickness indicate a diminishing sequence of open ground>canopy edge>canopied zone. In the snowmelt period, the decreasing rate of DH thickness shows canopied zone>open ground>canopy edge. 3) The DH grain size shows a decreasing trend at first stage (stable accumulation period - transition period) and then increase at the following stage (-snowmelt period). The rank of grain size keeps in the order of open ground>canopy edge> canopied zone after the stable accumulation period. 4) Due to the large snow thickness in the winter of 2009-2010, rounding depth hoar(DHxr) and rounding faceted particles(FCxr) are the two predominant grain shapes in DH, which accounted for 70%-80%. Hollow cups (DHcp) prefer to develop at open ground, while large striated crystals(DHla), hollow prisms(DHpr) and faceted particles (FCso) incline to grow at canopy edge and canopied zone. There are approximately 10%-30% congregate crystals in DH. The ratio declines at open ground and rises at canopy edge and canopied zone along time scale.
The section of Yangtze River in Jiangsu Province was selected as the research reach. Seven cross-sections of paleo-valley depositional sequences were established with 285 bore datum and 8 documents from the references, which were the NO.3, NO.1, NO.4 Nanjing Yangtze River Bridges, the Runyang Yangtze River Bridge, the Yangzhong Yangtze River Bridge, the Jiangyin Yangtze River Bridge and the Sutong Yangtze River Bridge. 8 age results of 14C and 1 age results of ESR were obtained through analysis of seven drilling cores samples near the Nanjing NO.4 Bridge and the Yangzhong Bridge. The results indicate that, in the Last Glacial Maximum (LGM), the incised-valley was cut down into bedrocks at the upper reach of Zhenjiang Province, and the paleo-channel of Yangtze River flows through old riverbed sedimentary facies at the down reach of Zhenjiang Province , and the paleo-valley formed partly deep cut in the Xiaguan-Qixia Mountain. The deep incised-valley at the depth of -63 m to -94 m was the Yangtze River valley during the LGM, the deep incised-valley channel was narrow and the river flowed swiftly at Nanjing reach. The width to depth ratio (
Settlement archaeology is a composit subject about spatial location and geographical distribution of settlement and relic and vestige. Conforming to some society organization principle, the prehistoric settlements congregated to kinds of settlement groups closely in space, which not only was a token of general life style of prehistoric person, but also provided a viewport and a platform for revealing and researching on the historical evolution in prehistoric society. The Luoyang area (mainly Luoyang basin) of the core of Central Plains was taken as a typical example and representative for studying the grouping pattern of prehistoric settlements and society evolution, and the research emphasized on the Era of the Yangshao and Longshan. Based on GIS , the data processing was done (including the digitalization and registration and database design and so on) firstly, and then the number ,scope , spatial distribution and space relationship of the discovered prehistoric settlements in the area were visualized with kinds of graphics and tables. And thirdly the spatial relationship of the settlements with topography and physiognomy were analyzed combined with some historical events and environment of the time. To be concrete, there were three results: More than 80% settlements located the area that gradient was lower than 3°,which showed the historical person were inclined to reside in the smooth area.More than 50% settlements located in the area less than 1 km far from the closest watershed and more than 90% settlements located in the area less than 4 km far from the closest watershed, which showed the prehistorical person were inclined to select the area where was moderate distance far from the closest watershed. The area of almost more than 60% settlements were 1~10 km2 moderately and the number and the area of the front 4 eras were balanced comparatively but that decreased in the Shang Era and increased largely in the West Zhou and East Zhou Dynasty, which were supposed to relate to some historical events. In this article, the space and attribute information were mined enough to reveal the modality characters of settlement group and union of settlement groups. Three factors were considered to assist and analyze the settlement modality: space distance between settlements, their scopes and some natural barriers (such as great river, jebel etc.). Based on the above analysis the settlements were plot out 24 settlement groups (in a group the distance among the settlements were generally short, and significantly greater than the mutual distance between the internal settlement ruins of the settlement group) and 5 unions of settlement groups (the Yi River, Luo River and Yiluo River were chiefly the partition boundaries ) on the Yangshao Era, which was a reflex of the society structure and class of the time.
Geostatistics is useful for characterizing and mapping spatial variability of heavy metal. The geostatistics method combined with geographic information system (GIS) was applied to the spatial variability of heavy metal in lake sediments in the Songnen Plain, then drawing the map of heavy metals by Kriging method. The geo-accumulation index (Igeo) and the potential ecological risk index were applied for assessing the status of sediment heavy metal pollution and the extent of potential ecological risk. The results indicated that the content of Mn(30.4-468 mg/kg) was lower than soil environmental background values of the Songnen Plain(484.96 mg/kg), but other five heavy metals were higher than the background values. The mean contents of Cu, Zn, Ni, Pb and Sr in lake sediments were 29.09 mg/kg (soil environmental background value was 17.78 mg/kg), 189.79 mg/kg (52.02 mg/kg), 35.07 mg/kg (23.65 mg/kg), 25.57 mg/kg (20.23 mg/kg)and 134.97 mg/kg (113.76 mg/kg). The spatial distribution map of heavy metal demonstrated that the distribution pattern of heavy mental in lake sediments was that the northeast region was hyper the southwest in the Songnen Plain, the contents of heavy mentals in the city of Daqing, Zhaoyuan, Anda, Qigihar, Dorbod and Nong’an were higher than others areas. Igeo indicated that the pollution extent of heavy metals followed the order that Zn>Cu>Ni>Pb>Sr>Mn, Mn was non-pollution and the pollution of Zn had been above mid-level(1<Igeo≤2), but others were at low-level pollution (Igeo≤1). The single potential ecological risk of heavy metals indicated all elements were in low- level risk(
From 1970s, many projects of land reclamation from the sea were implemented in the northwest coast of Bohai Bay successively. Therefore this region becomes the biggest zone of artificial land reclamation from the sea in China at present. It is necessary to monitor and analyze these changes accurately and continuously. Using the annual MSS/TM/ETM images from 1974 to 2010 and based on comprehensive analysis of GIS and RS, the spatial variance and quantitative changes of land reclamation from the sea in the study area were obtained. During the past 36 years, the main land increased 901.7 km2 which mainly reclaimed from tidal flat and offshore. The coastline increased from 224.9 km in 1974 to 536.7 km in 2010 and the barycenter of total reclamation area transferred 26.3 km from northeast to southwest continuously. Then, 5 phases were divided based on the annual change of land reclamation and some results could be concluded as follow. 1) the increment of coastline length was positively correlated with annual reclamation area. 2) the aim of land reclamation from the sea experienced several development courses: “saltern-oriented” →“combining saltern and aquaculture”→“combining port and port-vicinity industry”. 3) Tianjin Port with its port-vicinity industry zones and Caofeidian Port with its port-vicinity industry zones became the center and sub-center of land reclamation from the sea respectively.
There are many dams constructed in the Huaihe River basin which are drastically altering the natural hydrologic regimes of the river. In order to demonstrate the influence on the natural hydrologic regimes of the river by such intensive dams, the Bengbu Sluice which lies on the mainstream of the Huaihe River as a typical control node was selected to study the influence of the Bengbu Sluice and all its upstream dams on the hydrologic regime. Using Indicators of Hydrologic Alteration and Range of Variability Approach methods, hydrologic alteration at the streamgauge site was assessed to demonstrate the influence of dams on ecohydrological conditions in the Huaihe River basin. The results show that dams profoundly affect the Huaihe River hydrology, primarily through changes in the timing, magnitude, and frequency of high and low flows, ultimately producing a hydrologic regime that differs significantly from the pre-impoundment natural flow regime. They reduce annual peak discharges, decrease the ratio of annual maximum/mean flow, decrease the range of daily discharges, increase the number of reversals in discharge, reduce the daily rates of ramping, alter the timing of high and low flows, and change the timing of the yearly maximum and minimum flows. Dams in the Huaihe River basin have more drastic impact on low-flow events. In the post-dam period, large-scale cease-to-flow events began to occur and last for long periods of time in the basin, which is seriously destructive to the riverine ecosystem. The elimination of floods following impoundment has extirpated native riparian forest communities, subsequently reducing biodiversity and causing major changes in river food webs. It has significantly disrupted aquatic life cycles and contributed to adjustments in the riparian community structure, ultimately promoting the dominance of invasive exotics. Other components of the hydrograph and flow duration curve also have corresponding ecological responses, especially those associated with changes in the timing and duration of flows and in the rates of change and frequency of hydrograph rises and falls. The river ecohydrological targets for the Bengbu section defined by this study can support ecosystem management and restoration plans, and provide ecological operations for the Bengbu Sluice.
Maize is the main crop in the west of Jilin Province. According to the field experiments in the west of Jilin Province, this paper discusses the water requirement of maize growth and the changes of water source in different years based on the same soil and farm management conditions, namely, comparatively analyzes the dynamic change of maize production water footprint. It is useful for the rational utilization of water resources, the protection of ecological environment and the agricultural sustainable development. The results of the 3 years field experiments (2005,2006 and 2007)indicate that the major portion of maize production water footprint is green water with more than 80%. The blue water footprint is less than 1% and the gray water footprint is between 10%-20%. In the green water footprint, the effective precipitation footprint is more than 70% in the abundant rainfall year. By contrast, in the drought year it accounts for 50%, while in the extreme drought year, it only accounts for 30%. They will bring about an adverse effect on the soil moisture balance. During the 3 years, the blue water per unit weight of maize is about 0.005-0.006 m3/kg, which is lower than 1% of the maize water requirement per unit weight. The green water per unit weight of maize is 0.559-0.839 m3/kg, accounting for more than 99% of maize water requirement per unit weight. The gray water per unit weight of maize is 0.099-0.122 m3/kg. According to the study of water footprint of maize production, it clearly shows that green water occupies an important position in rain-fed agriculture and food security in the west of Jilin Province.
In order to better implement student-centered teaching philosophy in the field practice teaching of physical geography, this article proposed to develop probing platform systems for physical geography field practice by using GIS technology. The system changes the traditional proof-theory and cognitive-based practice model, improves the autonomy and initiative of students practice. The paper analyzed the needs of probing platform system for physical geography field practice, and according to the needs, designed frame and functions of platform system, and made in-depth study for the core technology of the system developed. Finally, Lushan physical geography field practice was taken for an example to verify the platform system. The results show that: 1) The system fully mobilized the enthusiasm of student practice, provided a set of mechanism for students to participate the entire practice process, so that students can actively explore the geography problem, really make student play a leading role in entire practice process. 2) The independent practice function of the platform is a strong complement for the traditional practice mode, it provides a platform for the ability for developing students ability and quality of innovation. In a specific practice process, it can flexibly allocate different independent practice program based on the basis and interest of students, and can achieve the principle of teaching students in accordance with their aptitude. 3) In the development process, the system improves scalability by using plug-in framework model, improves reusability by using object-oriented design methods, and builds the system application model by using GIS. 4) The platform system can improve the quality of practice, and enhances the learning autonomy for student, and has important application value.
