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1.
Assessment of soil erosion risk on the area alongside a road not only provides important guidance to prevent and alleviate soil erosion, but also reflects a road built on soil erosion. The area alongside the road from Simao to Jinghong is chosen as the typical case; spatial analysis of GIS and BP neural network of artificial neural network are used as the methods; 5 factors of 3 aspects, such as topography, climate and land cover, are chosen to assess soil erosion risk on the area alongside a section of typical road. The results are that the area proportion of easier erosion land (the value of erosion risk is from 2.5 to 3.5) is relatively bigger; and the erosion risk of an area alongside the road in a certain distance is higher than an area far away from the road. It shows that the road has an effect on soil erosion of the area alongside it; the effect can be directly or indirectly caused by road construction; and the effect is reflected by the land cover change (including land use and vegetation status) caused by road construction.  相似文献   

2.
In this paper, Kaixian County, situated in the hinterland of the Three Gorges Reservoir Region, was selected for the case study. Factors of soil erosion were obtained based on the technique of remote sensing (RS) and geographic information system (GIS). Combining with field survey, soil erosion data in the years of 1988, 2000 and 2004 which covered the period from the beginning of the Three Gorges Reservoir Project to nowadays were investigated through the judgment model established on soil erosion intensity. With the function of spatial analysis in the geographic information system, the analysis and appraisal of dynamic soil erosion changes were carried out, and the spatial characteristics of the vicious change were highlighted, and the main causes of the vicious change of soil erosion were explored.  相似文献   

3.
The eco-environmental frangibility is studied by choosing the factors of land use class change and vegetation cover rate, and the equation of eco-environmental frangibility and its evaluation system are established based on remote sensing (RS) and geographic information system technology (GIS). Four different years of TM images are selected to calculate land use change grads and vegetation cover rate, and the relationship between the two factors and eco-environment frangibility index are build, taking Fuzhou as an example. The character of times change and space distribution of eco-environment frangibility are described. The result indicates the area of eco-environment frangibility increased 2.6% in Fuzhou during twelve years, and expands from the region between infield and forest land to forest land in space distribution.  相似文献   

4.
Based on the collection of land use maps of three repre sentative years (1972, 1986 and 1995) with a scale of 1 = 100 000, which were derived from interpreted aerial photographs and field surveys, landscape pattern were studied in Wenchuan County of Aba Prefecture, northwest of Sichuan Province, China, Six land use categories were classified according to the actuality of the study area and digitized by manual with the assistance of Geographic Information System (GIS). Landscape spatial and temporal changes were analyzed quanti ficationally by a series of structure, shape, pattern indices, which indicated that grassland dominates in number of patch while both grassland and shrub-land dominate in total area of patch over time. During the last 23 years, the fractal dimension of grassland and shrub-land were decreased while the other types were increased. Highest dominance and fragmentation and lowest diversity characterized the landscape of 1972. In 1986, the landscape pattern had the highest diversity and lowest dominance and fragmentation, which is contrary to the pattern in 1972, Slight change of diversity, dominance and fragmentation has been displayed from 1986 to 1995.  相似文献   

5.
Effect of land use on microbial biomass-C, -N and -P in red soils   总被引:1,自引:0,他引:1  
Eleven red soils varying in land use and fertility status were used to examine the effect of land useon microbial biomass -C, -N and -P. Microbial biomass-C in the red soils ranged from about 68 rag C/kg to 225 mg C/kg, which is generally lower than that reported from other types of soil, probably because of low or-ganic matter and high acidity in the red soils. Land use had considerable effects on the amounts of soil Cmic.The Cmic was the lowest in eroded fallow land, followed by woodland, tea garden, citrus grove and fallow grassland, and the highest in vegetable and paddy fields. There was significant correlation between Cmic and organic matter content, suggesting that the influence of land use on Cmie is mainly related to the input and ac-cumulation of organic matter. Microbial biomass-N in the soils ranged from 12.1 Nmg/kg to 31.7 Nmg/kg andwas also affected by land use. The change of Nmic with land use was similar to that of Cmic. The microbial C/N ratio ranged from 5.2 to 9.9 and averaged 7.6. The Nmic was significantly correlated with soil total N and available N. Microbial biomass-P in the soils ranged from 4.5 mg P/kg to 52.3 rag P/kg. The microbial C/P ratio was in the range of 4-23. The Pmic was relatively less affected by land use due to differences in fertili-zation practices for various land use systems.  相似文献   

6.
Different from other similar studies, in this paper, most of the data were excerpted from historical archives and documents, and were used to study the spatiotemporal dynamics of cultivated land resources in China during the last 300 years. It is clear that these data may help reveal land use change dynamics and its regional differences, but they may be problematic due to the constraints of the original data in the Ming Dynasty, Conversion of Land Area for the purpose of collecting land taxes, and the deliberate or inadvertent omission of cultivated land area during land surveys, therefore, such data were adjusted to our need. In processing the data, we made great efforts to analyze the historical context of their sources and reduced the possible errors. The results show that the cultivated land area increased most quickly in the early Qing Dynasty, and slowed down after the middle Qing Dynasty, and then was stable in the late Qing Dynasty until 1949, and has been decreasing since then. It is also found that the cultivated land use varied greatly in different regions. The east of the country was cultivated much more heavily than the west, but in some western provinces cultivated land area increased more quickly. It is considered that the driving factors of such cultivated land area change include the increase of the population, the political issues, and the impacts of wars. Natural environmental factors and the introduction of new crops might also have affected the cultivated land use change in the past 300 years.  相似文献   

7.
The paper makes detailed analysis on the changing processes of the main types of land use in Three Gorges Reservoir Area through the techniques of RS (Remote Sense) and GIS (Geography Information System). Based on the theory of landscape ecology, many types of landscape pattern indexes are calculated and made correlation analysis. The results indicate that: in 1995 the ecological environment of Three Gorges Reservoir Area was the most vulnerable in the recent 50 years, but resumed in 2002; the landscape pattern diversity index, fractal dimension index and fragmentation index has close correlation with the area of land use/cover change (LUCC). The research also releases that the increase of the cultivated land, grassland and construction land deteriorates the landscape ecological pattern, while the increase of forest land area will help restore the landscape ecological pattern to its original state. The rapid change of grassland is an important index of the change of landscape pattern, because it has the most effect on change of landscape pattern index.  相似文献   

8.
This analysis studies changes in the variation 210Pbex inventory in soil in response to soil erosion on uncultivated land.A model was created to fit the response of 210 Pb ex inventory to variations in soil erosion rates on uncultivated land using the principle of mass balance.By numerical simulation of the variation in the soil erosion rate in soil of uncultivated land,we prove:(1) past use of what has long been considered the best method of determining 210 Pb ex levels over the past 100 to 200 years is not scientifically accurate;(2) the model shows that variation in 210 Pb ex inventory as a function of time varies according to the index law after variation of soil erosion rates in uncultivated land is considered;and(3) the time needed for the variation in 210 Pb ex inventory to reach a steady-state is affected by changes in the rate of soil erosion and the quality and depth of relaxation in soil of uncultivated land.The results of this research can guide efforts to measure soil erosion rates.  相似文献   

9.
Present monitoring and prediction of schistosomiasis's intermediate parasite, snail, are based on remote sensing image's spectral signatures, and the calculation result is in fact an incomplete-constraints solution. TM image of the Poyang Lake region on October 31, 2005 was combined with GIS thematic data (DEM, boundary of the Poyang Lake, vegetation, soil and land use) to make a prediction on snail spatial distribution in the region by remote sensing, geo-informaUcs and knowledge-driven modeling according to mechanism of snail occurrence. Result shows that with change of overall fuzzy membership of snail occurrence from high to low, snail occurrence of the snail samples of validation group goes up to 81% within 10% high fuzzy membership range, denoting high efficiency of the model in predicting snail occurrence.  相似文献   

10.
Qi  YongQing  Liu  JiYuan  Shi  HuaDing  Hu  YunFeng  Zhuang  DaFang 《科学通报(英文版)》2008,53(9):1423-1430
Wind erosion is one of the major factors of land degradation in the typical steppe region, northern Mongolian Plateau. Using ^137Cs tracing technique, we estimated the wind erosion rates of different pastures and abandoned farmland at Bayannur and Karakorum in Mongolia. The pastures and cutting grassland at Bayannur were slightly eroded by wind, with the rates of 64.58-169.07 t·km^-2.a^-1. The abandoned farmland in Karakorum, however, was strongly eroded by wind, with annual surface soil loss of 4.05 mm. a^-1, and wind erosion rates up to 6723.06 t· km^-2. a^-1. The total loss of surface soil due to wind erosion has been 17.4 cm since the cultivation of the steppe land in the 1960s. The wind ero- sion rate at the abandoned farmland was much higher than that at the typical steppe sites, showing that the cultivation led to serious wind erosion in the typical steppe region, northern Mongolian Plateau. By contrast, traditional livestock grazing resulted in less disturbance to the surface soil, and did not induce to devastating wind erosion, which plays an important role in maintaining the stability of the steppe ecosystem in the northern Mongolian Plateau.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

18.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

19.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

20.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

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