Studies on the evolutionary process and the inter-relations of the earth surface elements are a front field in the world. West China is an ideal area for conducting researches on the earth surface processes. This paper reviews the progresses in researches on the earth surface process in West China and the growth of the relevant research groups under the supports by National Natural Science Foundation of China.
Water Center of Chinese Ecosystem Research Network (CERN) is a management unit that manages the long-term water environment of CERN field stations, and it is also a scientific research group of the Institute of Geographical Sciences and Natural Resources Research (IGSNRR). Water Center always focuses its research on the application of the advanced measuring methods to ecohydrological processes field observation. The faculties of Water Center have made important progresses in the application of Lysimeter, eddy covariances techniques, experimental remote sensing techniques, large aperture scintillometer applications, and stable water isotope techniques. At the same time, the modeling researches on surface evapotranspiration have also developed from the early empirical model to the mechanism model based on water-carbon coupled processes. The further development of measuring method on ecohydrological processes should place emphasis on the combination of the flux observation technique and the in situ vapor isotopic analyzing technique, and the combination of local measurement and the remote sensing information.
Urbanization may have affected the surface air temperature records at many stations in continents, especially in industrial regions like Europe, North America and East Asia. However, this issue is still under debate at present, especially at regional and global scales. Based on an overview of researches on urbanization effects on surface air temperature series mostly in the continents of northern Hemisphere, the nature and intensity of urbanization effects at different spatial scales are summarized and assessed. At city and local scales, most studies have found obvious urbanization effects, with big cities showing the most significant urban warming. At regional scale, the studies focused on mainland China and the United States also have showed significant urban warming in varied extents, in spite of the fact that a few studies have claimed an insignificant urban bias. It is obvious that the researches with robust methods to select reference stations have generally found significant urbanization effect on surface air temperature trends. For global or hemispheric average temperature series, researches are far from enough at present, but they have mostly indicated that the urbanization effect may be minor or insignificant, and it may have not exceeded 10% of the total warming observed. Studies have also found that the urbanization effect changes over time and regions. In East Asia, including China, Korea and Japan, urbanization has had very significant impact on surface temperature trend during the past half a century, but in Europe the significant urbanization effect might have occurred in the early 20th century and even the late 19th century. At present, there are still many problems and difficulties on the study of urbanization effect on temperature series, including the limited areas and time periods studied, radically different selection criteria of reference stations and imperfect methodology for urban bias adjustment. To solve these problems in the near future will help promote the progress of research.
The aquifer system of karst has features of complexity and multiplicity, and the researches on karst hydrological effects and water resources forecast are difficult. A number of models have been developed in the karst areas to simulate surface runoff, underground dynamics and transfers between them since the 1960s, which include black-box models, conceptual models and physical models. Each type can address specific issues in the field of simulating runoff, and meanwhile, has its own drawbacks and limits. (1) Blank-box models, including kernel function, regression equation, stochastic models, artificial neural network and wavelet theory, are often well adapted to decipher their overall behavior, but they have the disadvantage of not providing any understanding of the physical mechanisms of the aquifer and lacking predictive power. (2) Conceptual models are based on simplified physical interpretation of the processes of transforming input to output, including reservoir models and multiple exponential recessional response elements. In general, the molders of this category are ideal in modeling cases with insufficient data, but they cannot apply localized information for water level fluctuation. (3) Physical models are considered to be those which can simulate both diffuse flow in the matrix and the flow in the pipes, these models require very good knowledge of the aquifer systems and they have too many parameters need to be calibrated. At present, in terms of spatial/temporal complexity, data scarcity and physical aquifer properties, a variety of common issues still trouble karst hydrological modelers. The tendencies of future karst hydrological models mainly manifest themselves in the following aspects: addressing problems in terms of physical features of hydrologic behavior and nonlinearity of karst aquifers, studying karst water cycle, analyzing the characteristics and regional differentiation of all storage forms, applying new technology, methods and distributed models to define quantitatively and precisely the distribution of subsurface drainage, developing hydrological models which can be applied to many karst areas, establishing optimum parameters database, and incorporating the eco-hydrology response and water resources assessment in hydrological models.
Rill erosion plays an important role in soil erosion process in loess hillslopes. It is a quantum leap during the process of soil erosion on slopes, and also is the beginning of a qualitative change in the process of soil erosion. On the basis of studying many papers, the authors review the study of factors and critical conditions of rill erosion. Rainfall and runoff, soil, topography, soil surface characteristics and land management all have their impact on rill erosion. On the one hand, researches use a variety of parameters to represent the impact of rainfall and runoff, soil, topography and land management. On the other hand, there are two forms of soil surface characteristics, namely, surface roughness and surface soil crust. The studies on the impacts of both of them are still in a qualitative research stage, and some studies have shown they can weaken rill erosion, the other studies concluded that they would exacerbate the occurrence of rill erosion. The generation of rill on the slopes needs certain conditions, and the critical runoff, soil and terrain conditions have their corresponding research results. The critical conditions for the generation of rill are not numbers, but are related to many factors. Critical conditions for rill erosion are not fixed values, but all of them should be a comprehensive index of other factors. At the same time, the future possible research direction and contents of the influencing factors and the critical conditions of rill erosion are pointed out. More experiments and field observation data are needed. In rill erosion factors research, the following points need further works: (1) the quantitative analysis of the impact of rainfall and runoff on the joint action of rill erosion; (2) screening key indicators to represent the effect of soil, topography and land management factors; (3) an in-depth study on how the soil surface characteristics affect rill erosion, and a quantitative analysis of the impact of surface roughness and soil crust on rill erosion; (4) the interaction of various factors with the impact of rill erosion. Meanwhile, the studies of critical conditions of rill erosion need more investments, which include: (1) exploring the critical rainfall conditions for rill erosion, and finding out its relationship with critical runoff conditions, (2) a systematic study on the critical conditions in different areas, to obtain a judgment with strong applicability about whether rill erosion will occur.
The adaptability of ecosystems to climate change is critical to the projection of future vegetation dynamics and ecosystem functions though it is less studied than the impact of climate change on ecosystems, such as productivity and pattern of vegetation. The time lags of vegetation response to climate change and the relationships between climate and vegetation were used in the current study to simulate the dynamic responses of vegetation to climate change. We used the change direction of vegetation shift to assess the adaptive capacity of vegetation to climate change under the baseline climate condition and the future climate change scenarios, respectively. The results suggest that the vegetation without the capacity to adapt the contemporary climate are most distributed in the transition areas of ecosystems, and the vegetation type takes negative shifts in those areas. Such areas includes the transition zones between forests and shrublands, grasslands and deserts, and the percentage of those areas accounts for 5% of China mainland. Some of the ecosystems located in northern China with forest-shrubland ecotones, Inner Mongolia and eastern China with shurbland-grassland ecotones, and southern Tibetan Plateau with grassland ecosystems, accounting for about 35% of the total area, may not be very well adapted to the contemporary climate. The vegetation will probably degenerate. By the end of this century, most vegetation can adapt to the future climate based on the scenarios of IPCC-SRES-A2 in China. The future climate in northwestern China will be more favorable, and about 84% of vegetation shift will be positive change. Our results also indicate that vegetation in northwestern China is most likely to improve. As to potential change of vegetation by the end of this century, 79% of the vegetation will be likely to adapt to the climatic conditions, but some grassland ecosystems will be threatened by climate change, including those in the southern part of the Tibetan Plateau, Inner Magnolia, and some areas in northwestern China.
Based on the research results in the field of predictions in ungauged basins (PUB) available from the literatures and our own research experiences in PUB, the methodology of PUB is generalized to include "borrowing", "replacing" and "creating" methods, according to the logic of a Chinese saying: "even a clever housewife can not cook a meal without rice". Borrowing method is defined as the method to get the data by transplanting the data from a similar region or doing interpolation among the data from the neiboughood area. Replacing method is defined as the method to mine the target data from the related information either from the same research area by simulation, assimilation and interdisciplinary studying or from other areas by upscaling and paired-catchment analysis, all with similar geographic characteristics. Creating method is defined as the method to get the data via field or indoor observation. By combining the above research methods available so far, some clues for breaking through the barriers of PUB research to find the right solutions are proposed.
Rainfall temporal-spatial variations are very important for the development of agriculture production and social-economy. Based on the precipitation data of 85 surface weather stations in Hebei province from 1965 to 2005, the annual rainfall change characteristics under different time scales were analyzed by the Morlet wavelet analysis method. The results showed that three periodic oscillations (18-year, 8-year and 4-year) existed in the annual rainfall variation, and 18-year scale mainly in the 41-year period, but 8-year in the 1990s and 4-year in the 1970s. Also, there were 5 dry-wet processes for the 18-year scale and 10 dry-wet processes for the 8-year scale. A clear distinction for multi-time scales characteristics of annual rainfall occurred in different spatial areas. The large-scale of 12-18 years and meso-scale of 8-12 years were revealed in the northern and central-eastern parts respectively, while a small-scale of 3-8 year period was found in the western part of Hebei province.
Based on database technology, GIS technology and software engineering methods, this paper tries to design the database functionality of "China's land-based water system comprehensive simulation and virtual reality platform", which is the core software platform of the CAS Knowledge Innovation Program key project “Trans-basin water transfer and its impact on terrestrial water cycle and water safety". Using GIS software and commercial databases, a "multi-source database for regional water system" is established, with the diversity of spatial distribution, time scales, and data format, based on the integrated spatial-temporal strategy and the multi-database establishment frame, which effectively eliminate the effect of information silos, to achieve comprehensive utilization of data related to trans-basin water resources, and to provide integrated data support services for the platform.
As one of the main terrestrial ecosystems, grassland ecosystem has suffered the extensive effects from human activity and global change. These effects not only have an influence on aboveground process such as plant growth and plant community dynamics, but also exert a profound influence on multiple belowground processes simultaneously. Therefore, soil microorganism may be a good indicator to understand the response of the aforementioned belowground biological and biogeochemical processes to the changes of outside disturbances. Soil microbial biomass is an important parameter to character the soil microbe activity and size. Meanwhile, it is also the most active component of the soil organic carbon pool, and plays an important role in indicating the minute changes in soil system and is of great significance in the research of soil bio-chemical processes. Here the effects of natural factors (soil temperature, soil moisture and soil pH), human disturbances (grazing, grassland reclamation and fertilization) and global changes (elevated CO2 and global warming) on soil microbial biomass of grassland ecosystem are presented. So far, the researches about the effects of natural factors and external disturbance on soil microbial biomass still have a lot of uncertainties, so long-term field studies, multiple factors controlled experimentation and nitrogen input studies should be strengthened in the future studies. Besides, new technologies and methods to determine soil microbial biomass are also expected to be developed.
Diffuse phosphorus discharge from agricultural nonpoint sources has become one of the main causes of eutrophication of surface water. Agricultural NPS pollution can be widely distributed and there is an uncertainty in temporal and spatial distribution, so it is difficult to control and prevent it. Now the valid way to improve the efficiency of control is identifying high risk areas of P loss and then making corresponding measurements. PI based on GIS is a simple risk assessment tool and can identify the high risk areas effectively. This paper reviews the key techniques of P index, including the P loss factors which are taken into account in P indices and modifications of calculation of PI value, and then analyzes the using extent and scale.
We have measured the diurnal changes of dune CO2 concentration under different depth by using the infrared monitoring instruments in Minqin County in 2009, and combined the results with simultaneous temperature data. The results show that the CO2 concentration of -2 m and -4 m always greater than that of -1 m. The diurnal CO2 cumulative concentration from this research can be ranked as fixed dunes > semi-fixed dune > moving dune. The CO2 cumulative concentration is greater at daytime than at nighttime. For fixed, semi-fixed and moving sand dunes, the CO2 concentration has a changing law of“low to high and then to low”from the morning to the next morning, which is basically the same as the change of temperature, but the change of the former is later than that of the latter. There is a significant positive correlation between the CO2 concentration of dunes and atmospheric temperature, and temperature is the main factor determining the changing law of the dune CO2 concentration. In addition, the diurnal concentration of CO2 can be changed due to the difference in soil conditions, such as soil moisture, light and wind speed. So, it is of great significance to conduct research into the cause of global warming and the impacts of destruction of vegetation on atmospheric CO2, which can help to find out the changing law of dune CO2 concentration in 24 hours.
The process of Chinese social-economic development was a long struggle history. Flood, drought and locust plague were the three biggest natural disasters in Chinese history. Flood and drought which had a close relationship with climate change have been studied by many researchers for a long time. As for locust plague, more attention should be paid to it. Accordingly, through collection and interpretation of Chinese historical documents related with locust plague, we set up a Chinese historical locust plague database according to which the trend and characteristics of locust plagues were disclosed. As for the three subspecies of migratory locusts in China, we made a sublevel regionalization map of them. According to the database and the map, we constructed many historical locust plague sequences. More work was done to deal with comparisons between locust plague sequences and sequences of other natural disasters, social crises, and climate proxies—mainly temperature and precipitation. Finally, we drew a preliminary conclusion of the social influence and environmental significance of historical locust plagues, to which ecological explanation was also given. We did several comparisons between locust plague sequence and war sequence, epidemic sequence, dust storm sequence, rice price index, and flood sequence of Huaihe River. The results were as follows. Firstly, locust plagues had close correlations with wars and epidemics, which indicated the causality among them. Secondly, locust plagues had a good coherence with dust storms, but it did not mean that cold background was indispensable for locust plagues. Thirdly, locust plagues in Anhui had no overlapping year with floods of the Huaihe River, which in reverse proved the coherence between locust plague and drought. Fourthly, we found that rice price ascended always with a 1-3 year lag after locust plague, which inspected and verified the fact in history. Through construction of next year tables of warm and cold winters in North and East China, we found the recurring probabilities of locust plagues in the two tables were 89/126=0.7063 and 64/85=0.7529, with a difference of 0.0466. The result indicated that locust plague did not have a positive correlation with either warm or cold winter, and locust plague sequence could not be used to reconstruct winter half-year temperature. In a worldwide field of view, we made comparisons between several representative locust plague sequences and typical climate sequences. We found that locust plagues of Core Region had a good tele-connection with ENSO, and locust plague still had bad coherence with temperature, but good with drought. Ecological explanation was given. In summary, our study was an integrated study on social influence and environmental significance of locust plagues in China during the historical period, and the study was an integrated work based on historical data, geographical methods and ecological explanation.
Drought has been a crucial meteorological factor which limits the agricultural development and eco-environment construction in the northwest area of China. In the past decades, many Chinese scientists tend to explore the cause of drought from the perspective of biophysical aspects, while the accumulated body empirical evidence identifies that social system has enormous impacts on disarsters (drought) as well. Nature and mankinds are tightly linked, and they are coupled systems which can be termed as social-ecological systems. What can we do to gain a deep understanding about the interacting processes and the mechanisms bewteen nature and society, and then build a scientific foundation for drought defying decision-making? Resilience, as a new theory, provides an idea to solve this problem. Resilience refers to the capacity of a system to absorb disturbance and reorganize while undergoing changes, so as to retain essentially the same function, structure, identity, and feedbacks. Since resilience is a buffer in the social-ecological systems to the external perturbations and shocks, the management that builds resilience can sustain social-ecological systems when facing surprise, unpredictability, and complexity. Yet many studies mainly focus on description and qualitative analysis, which cannot offer practical instructions to solve specific problems, therefore, the attempt to quantify resilience of the systems, which can prevent social-ecological systems from sliding into some undesirable stable states, has become an imperative trend. Based on the statistic data and remote sensing images, the resilience of the social-ecological system to drought in Yuzhong County of Gansu Province during the last 15 years was calculated by integrating statistics approaches and GIS. The results indicate that the resilience of Yuzhong County depends on the interactions between internal factors (social, economic and natural) and external factors (aridity), and also highlight the need for local managers to be aware of how differently towns respond to drought, which is of great significance for managers to make robust managing strategies.
Grassland is one of the main terrestrial ecotypes and the dynamic change of its soil respiration can directly affect the global C cycle. Grassland responses more rapidly to global C cycle than other terrestrial ecosystems. Therefore, grassland soil respiration could be firstly affected by global climate change and land use change. The objective of this paper is to provide a scientific review on grassland soil respiration response to global change and human activities. The elevated atmospheric CO2 and rising temperature can both stimulate, suppress or show no significant effect on grassland soil respiration, depending on whether changes of soil moisture, soil available N and other related factors occur or not. The Q10, which is the temperature sensitivity index of soil respiration, of grassland soil respiration is affected by soil temperature, soil moisture, precipitation, soil depth, soil organic carbon, altitude, land use patterns, time scales and other related factors. This implies that the relationships between grassland soil respiration and soil temperature is affected by other factors and grassland soil respiration is actually affected by the combined effects of multiple factors. Increasing precipitation will generally stimulate grassland soil respiration. However, the decrease of soil temperature and soil permeability which are caused by precipitation will reduce soil respiration amount. Due to grazing intensity, grazing frequency and grazing forms, the impact of grazing on soil respiration appears to increase, decrease or show no significant effect. The effects of clipping on soil respiration and its components (soil heterotrophic respiration and root respiration) are different. When agricultural reclamation occurs in grassland, soil respiration could enhance and the soil carbon will lose approximately 20%-50%. Fertilization might increase, decrease or show no significant effect on grassland soil respiration, according to fertilizer type, loading levels and so on. In the arid and semi-arid regions, irrigation might promote grassland soil respiration. However, the integrated effects of these global changes, i.e., elevated atmospheric CO2, rising temperature, increasing precipitation, grazing, land reclamation, fertilization and irrigation, are unclear. Therefore, the research on the respondence of soil respiration to global climate change and land use change should be enhanced in the future.
As is well known, there exist similarities and differences among geographical regions, and zonality is a universal theorem governing geographical patterns. Physio-geographical regional system is a hierarchical system, which is formed by division or combination of natural features based on geographic relativity and geographic zonality. Researches on physio-geographical regional system aim at observing and studying natural complex of the earth’s surface, revealing rules of regional differentiations and exploring formation, development, division, combination, relativity and demarcation of natural regions at different scales, from a regional point of view. As a radical method to obtain geographical information, physio-geographical regionalization has always been studied and widely used by geographers. Studies on physio-geographical regionalization in China have made great progress in principle, methodology, and theory since the 1930s. It could provide a scientific basis for social and economic development and planning, and conservation, improvement and rational utilization of natural environment. Based on brief review of physio-geographical regionalization at home and abroad, the paper summarizes the characteristics of researches in recent years: various types of elements; distinct ecologicalization in comprehensive natural regionalization; a complete series of spatial scales; scarce creativity in technology and methods; emphasizing regionalization methodology; enhancing application of regionalization schemes. Then, the paper analyzes academic problems in the present researches: lack of epistemological study; weak methodological study. Finally, the paper explores the prospects of physio-geographical regionalization: continuous increase in requirement at the national level; strengthening the standardization of regionalization, and raises several trends in geographical regionalization.
Scale issue is a focus but also a difficult theme in the driving forces analysis of land change. While statistics is very popular in analyzing drivers of land change, there is no particular research on the impact of scale in this domain. This article summarizes the methods often used in the driving force analysis of land change, recognizes five scale issues needed to concern. They are the impact of 5 situations (the extent of the study area, the grain size, the time range, the time period of data, and the classification accuracy) on the analysis results when using the term of‘scale’, and all of these 5 situations can be concluded into data aggregation. If the impact of data aggregation is not treated correctly, the potential dangers exist in two aspects: (1) the results is meaningless, (2) the policies based on the analysis are incorrect and harmful. So far, there are 3 approaches to solve this problem: (1) basic entity approach, (2) sensitivity analysis approach, and (3) frame-independent analysis approach. These approaches can be applied and more researches are needed in the domain of the driving force analysis of land change.
According to the interpretation results of composite TM images of the Yanhe River Catchment and Ansai County in 1990 and 2000, and based on the field investigation on the eco-construction activities from 2000 to 2006 in this area, the land use/cover change and its driving factors in the Yanhe River Catchment and Ansai County were analyzed at both catchment and county scales. The driving force models of cultivated land area change were established at both catchment and county scales. Based on the relationship among the common driving factors at different scales, a scale conversion method for cultivated land changes at different scales was established. The results showed that, for land use/cover change models at different scales, they could be converted based on the quantitative relationship of key driving factors, no matter how complicated the models were. The study results would put new insights into the scale conversion research of land use/cover change.
Spatial expansion of urban construction land is a primary expression of urban development, and the changes of structure and quantity of construction land will impact the using efficiency of construction land. This paper utilized the land use maps of the Three Gorges Reservoir Area of the years 2000 and 2005, and ArcGIS to analyze the spatial transformation between urban construction land and other land use types in the region. The expansion of urban construction land has led to a rapid reduction of cultivated land. Some 6004.77 hm,sup>2 cultivated land were transformed into urban land. The average area of plots reached 115.48 hm,sup>2. The paper analyzed the regional difference in occupying agricultural land for urban development. In the region of Banan District, Jiangbei County and Chongqing urban area, comparatively larger area of agricultural land is occupied each year. Riparian buffer was established to analyze the intensity of urban land expansion. In the reservoir area, urban land expansion mainly lies within a radius of 0-10 km from the buffer zone. Combining the analysis of the changes in urban land use, adopting DEA model and assessing construction efficiency by applying efficiency value, DEA validity, and scale efficiency, we made a benefit evaluation of construction land use, and used ArcGIS to spatialize efficiency value, DEA validity and scale efficiency. The study showed that the urban construction lands with high efficiency values were distributed in the downstream reservoir area and Chongqing urban area. The overall efficiency of urban construction land is improving, and the disparity among regions is gradually narrowing. Finally, this paper gave some suggestions on improving the efficiency of urban land use in the reservoir area.
The Qomolangma National Nature Reserve was established on March 18, 1989. In March 2005, it was added to the global biosphere protected area network. There are relatively few domestic studies on its vegetation cover change. In this paper, using MODIS NDVI data from 2000 to 2009, the spatial distribution and variation of vegetation cover on the southern and northern slopes in the Mt. Qomolangma Nature Reserve were studied based on the linear trend analysis of the growing season NDVI peak value of each pixel by pixel level. The results showed that: (1) For significantly improved area and slightly improved area of vegetation cover, the average annual growth rates of NDVI-Max are 3.06% and 1.25% respectively; For significantly degraded area and slightly degraded area of vegetation cover, the average annual reduction rates of NDVI-Max are 2.82% and 1.09% respectively. (2) The vegetation cover on the southern slope of the reserve showed an increasing trend on the whole from 2000 to 2009, and 22.59% of the study area improved greatly, 19.05% improved lightly, and 24.75% kept stable; while on the northern slope, the vegetation cover showed a decreasing trend on the whole, and 19.5% of the study area degenerated greatly, 24.43% degenerated lightly, and 38.12% kept stable; (3) Among the eight landuse types covered with vegetation on the southern slope, the vegetation cover of dry farmland in mountainous area showed a decreasing trend, and that of the others showed an increasing trend; while for the 10 landuse types covered with vegetation on the northern slope, their vegetation cover showed a decreasing trend.
In this study, we use three scenes of Landsat Thematic Mapper (TM) images, including those of 1988, 1998 and 2006, to detect the expansion of construction land in the Pearl River Delta. And then we use the spatial analysis function of GIS to specify the impact of site factors on it, focusing on the effect of the landform and the distance from the city center, roads or coastlines. Firstly, we derived land cover maps from TM data by artificial visual interpretation method (AVIM). Then, we overlaid the distribution maps of construction land with the topographic map and analyzed the pattern of construction land expansion in the buffer zones around urban centers or along main roads and coastline. The results show that the site factors, such as the landform and the distance from the city center, roads or coastline, indeed have a prominent influence on the expansion of the construction land. Due to the centralization and diffusion of the city center, the expansion of construction land reaches its peaks at two spheres surrounding the city center. The inner one represents the development of suburbs, indicating the spilling over of the city center and the rapid development of the suburbs, while the outer one manifests the development of the industrial zones and the construction of the satellite cities in the outer suburbs, showing the pattern of urban expansion like leapfrog. Thus, suburb is the preferred location for construction land development and the construction land there expands most furiously, indicating the intense interaction between urban and rural areas and also reflecting the essence of the process of suburbanization in large cities. The influence of the distance from the roads or coastline reflects, in essence, the impact of the transportation accessibility on the expansion of construction land. From the quantitative analysis results, we can see the location close to roads or shoreline is the preferred location for construction land development, resulting in the distribution pattern of the construction land gathering along the roads or coastline. Landform also has an obvious influence on the expansion of construction land. Plain area is the preferred location for construction land development, and also the area for the high-quality farmland to agglomerate, therefore triggering the conflicts between the construction land developmet and farmland protection. In short, site factors act as the indicators for the expansion of construction land, leading it to expand to the location such as suburbs, plains as well as the areas nearby the roads or coastline. Site factors play an important role in indicating or restraining the expansion of construction land, determining the direction, scale, intensity and speed of the expansion of construction land.
Taking Wuhan City Circle as a case, this paper discussed the application of the regional partition asynchronous cellular automata model in the layout optimization of cultivated lands according to the regional heterogeneity of the socio-economic development in the counties in the Wuhan City Circle. The model determined the asynchronous evolution rate according to the construction land demand priority of the counties, set up the regional conversion rules according to the laws of land use change, food self supporting capacity and satisfied degree of construction land demand of the counties, and determined the overall and regional ultimate arrangements according to the food safety of the whole region and the construction land demand of each county, so as to realize the layout optimization of cultivated land use of the Wuhan City Circle in 2020. The optimization result indicates that the total quantity of the cultivated land in the Wuhan City Circle can meet the demands of the food safety of the whole region. The construction land demand can be met in the regions with higher construction land demand priority degrees, including the districts in Huangpi District, Yingcheng City, Xinzhou District, Hanyang District, Qianjinag City, Huanggang City, Ezhou City, Xiaogan City, Wuchang District, Xiantao City, Huangmei county, Wuxue City, Yangxi County, Xianning City and Chibi City. The construction land demand priority degree is relatively low in Tuanfeng and Tongcheng counties, but the construction land demand is smaller, and thus the construction land demand can also be met in these regions. In other counties (or cities, districts), the construction land demand is not fully met due to the conflicts between the construction land demand and the construction land demand priority degree. The result indicates that the regional cultivated land layout optimization based on the partition asynchronous cellular automata model. which considers the heterogeneity of demand for construction land on the basis of cultivated land protection and food safety of the whole region, can coordinate the relations between food safety and economic development and set up a reasonable configuration of construction land layout and cultivated land protection.
Taking the Maotiao river watershed as the area for a case study, based on environmental economic theories and methods, this paper calculated the soil erosion economic loss under different land use structures in different years in the study area, and analyzed the current situations of soil erosion economic loss, the dynamic change chanracteristics of soil erosion loss, and its relationship with land use structure. The results showed that (1) the total economic loss from soil erosion reached 37381.64×104 yuan in 2007 in the study area, and the loss of nitrogen, phosphorus, kalium and organic matter acounted for 90.26% of the total economic loss, which was 33739.98×104 yuan. Among different land use types, soil erosion economic loss was the highest in dry land and grass land, accounting for 47.08% and 44.24%of the total loss, respectively. The economic loss was higher in the north and southwest of the study area. (2) The soil erosion economic loss changed dramatically during recent 30 years, with an intimate relationship with land use structure. The soil erosion economic loss increased by 3092.98×104 yuan during 1973-1990, or 8.74%, and decreased by 11162.43×104 yuan during 1990-2007, or 22.99%. Dry farmlands and grasslands were the main land-use types that caused soil erosion economic loss. Qingzhen, Pingba and Xiuwen are the main regions that should take measures to prevent soil erosion in the study area.
