| Desertification is one of the worldwide eco-environment problems.According to the statistics of United Nations Environment Programme(UNEP),1/3 of the land area are affected by desertification in the global.Pastoral area,taking use of natural grassland as a resource operate the animal husbandry and taking grazing as the main means,is based on the vast natural grassland and produced goods,such as livestock,breeder,draft animals.Oasis is the most concentrated and the most frequent area of human activity in arid areas,so the analysis of pastoral and oasis desertification is so necessary and urgent.In this study,the pastoral and oasis,respectively,take Maqu County and Minqin County for example,the TM image as the data source,RS and GIS as the technical means to study the evolution processes and regulations of desertification in Maqu County and Minqin County from 1975 to 2015,combining with the meteorological and socioeconomic data to explore the driving forces of pastoral desertification and oasis desertification and having a comparative study of pastoral desertification and oasis desertification.The preliminary findings are as follows:1.The temporal and spatial changes of desertification in Maqu county and Minqin county from 1975 to 2015.The total desertification area of Maqu County decreased 487.2km2 and Minqin County increased 203.39km2,but the degree of desertification decreased in Minqin County.Maqu county,taking 1995 as turning point,which desertification was expanding during 1975 to 1995 and reversing from 1995 to 2015.The desertification of Minqin County was expanding from 1985 to 1995,and the remaining three periods for the reversal of desertification.Among which,the effect of desertification control was significant from 1995 to 2005 in Minqin County and in Maqu County.The land use reserved a slow changing trend in Maqu County and Minqin County.The moderate desertification migration distance in Maqu County was the farthest,but the light desertification migration in Minqin County was the furthest.2.Analysis on the driving forces of desertification in Maqu County and Minqin County.The changes of temperature,precipitation and relative humidity in the climate factors of Maqu County and Minqin County indicate that the climate of Maqu County has gradually developed into the warm and dry direction and Minqin County has gradually developed toward the warm and wet direction,which further indicating that the climate condition of Maqu County is not conducive to the reversal of desertification and conducive to the reversal of desertification in Minqin County.Combined with the human factor,using the principal component analysis method inferred that from 1975 to 2015,the highest factor loading of the first factors of Maqu County and Minqin County were the total population and the number of sheep at the end of the year.After adding two factors of cultivated land and groundwater exploitation,it concluded that the highest factor loading of the first factors were ground water exploitation;From 1975 to 1995,the highest factor loading of the first main factors were the total population in Maqu county and Minqin county.From 1996 to 2015,the highest factor loading of the first main factors were the number sheep at the end of the year in Maqu county and GDP in Minqin county.In summary,the occurrence and development of desertification was the interaction of human activities and climate change in Maqu County and Minqin County from 1975 to 2015,and the main driving force was the unreasonable activity of human beings.3.A comparative study on desertification in Maqu County and Minqin CountySimilarities: In the aspect of the temporal and spatial change and monitoring time of Maqu county and Minqin county,the largest desertification area and the highest desertification degree was in 1995.The land use reserved a slow changing trend.The mainly land changes of desertification are stable.As for the desertification distance of gravity shift,generally speaking,moderate desertification and light desertification migration distance is relatively far in each time period.Based on the analysis of the driving factors of Maqu County and Minqin County,it can be concluded that highest factor loading of the first main factors were human factors from 1975 to 1995,1996 to 2015 and 1975 to 2015,indicating that human factors play a leading role in the occurrence and development of desertification in Maqu County and Minqin County,and climate factors also have a catalytic role.Differences: In the aspect of the temporal and spatial change and monitoring time of Maqu county and Minqin county inferred that,(1)the total area of desertification in Maqu County decreased 487.2 km2,and the total area of desertification in Minqin County did not decrease,but the degree of desertification decreased.(2)Maqu County,taking 2005 as a turning point,before 2005,which the dynamic degree of comprehensive land use of was continuous improve,and the dynamic degree of comprehensive land use in Minqin County is increasing during 1975 to 2015.(3)During 1995 to 2005,desertification has significantly improved in Maqu County,and the reversal area was more than 24 times as much as the development area.During 2005 to 2015,desertification had significantly improved in Minqin County,and the reversal area was 4.23 times as much as the development area.(4)The desertification distance of gravity shift in Maqu County from large to small order was moderate desertification>light desertification> non-desertification.The desertification distance of gravity shift in Minqin County from large to small order is light desertification> moderate desertification> non-desertification>severe desertification.After the analysis of driving factors of desertification,It can be concluded that from 1975 to 1995,the highest loading factor in the second and third main factors of Maqu County were annual precipitation and annual sunshine hours respectively.The highest loading factor in the second and third main factors of Minqin County were annual sunshine hours and annual precipitation.From 1996 to 2015,the highest loading factor in the first main factor of Maqu County and Minqin County was the number of sheep at the end of the year and GDP respectively.Although the highest loading factor of the first main factor was the total population in Maqu County and the number of sheep at the end of year in Minqin County,and considering all the factors selected in Minqin County,the highest loading factor of the first main factor was groundwater exploitation.Therefore,by controlling the population and groundwater exploitation and other human factors,you can control the occurrence and reversal of desertification. |
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