| Xinjiang is located in the Euro-Asia continent as inland and away from the sea,In general,a semi-arid or desert climate prevails in XinJiang,and ecological environment is very delicate.Considering that ecological environment state can be largely reflected by the Fractional vegetation cover(FVC),regional environment changes can be revealed by studying on FVC,change.Up to now,many researchers have discussed FVC,and the relationship between FVC and climate using remote sensing technology,but the study of quantifying the influence of human factors on the vegetation cover change is relatively not enough,so this paper use the Geographic detector model to quantitativly evaluate the effects of natural and human factors on the vegetation cover change,not only analyzed the relative influence of single factor on the vegetation cover,but also analyzed the interaction effect on vegetation factors.The GIMMS NDVI3g(1982—2011)datasets were used to access the trend of vegetation variation in Xinjiang Region.Firstly,the yearly-scale time series remote-sensed data had been reconstructed by Maximum Value Composites method.The spatio-temporal patterns of vegetation and its change tendencies were depicted by cumulative anomaly,regression trend analysis and percentage changes method.Secondly,this study had used geographical information system techniques and a geographical detector model to explore the spatial consistency of nature factors and their interactions in relation to vegetation change in Xingjiang Regions.Nine factors,namely,precipitation,temperature,sunshine duration,wind speed,altitude,slope,aspect,vegetation types and soil types.Finally,this study had applied geographical information system techniques and a geographical detector model to identify the relative and interactive impacts of human factors on vegetation change.Human factors,namely,total population,density of population,GDP,per capita GDP,gross output value of farming,gross output value of animal husbandry,per capita net income of rural households,per capita disposable income of urban households,total yield of grain,per capita yield of grain,sown areas of grain,total power of agricultural machinery,effective area of irrigation,consumption of chemical fertilizers and numbers of livestocks.The main conclusions were as follows:1.Spatially,Xinjiang vegetation cover was turning better.In the Tianshan,Altai mountain and the oasis,vegetation cover was good and appeared improvement trend because of the sufficient water;In the desert area,as Tarim Basin,vegetation cover was poor and appeared degradation trend.2.Temporally,Xinjiang vegetation cover was showing a significant upward trend.From the perspective of each time period,before the early 1990s,vegetation cover was deteriorating,after 2008,vegetation cover was improving,and it was a volatile period during the middle time period.3.Precipitation,soil types and vegetation types was the main natural factors affecting vegetation changes,followed by temperature,sunshine duration and the altitude factor;although wind speed,slope and aspect affected spatial-temporal distribution of water-heat factors,the influence of the individual factor on vegetation change was very small.Therefore,precipitation,soil types,vegetation types,temperature,sunshine duration and altitude can be the natural indicators affecting the vegetation coverage.4.Every natural indicator has its own appropriate range or type,among them,for precipitation 316.20?504.08mm,for temperature 0?5?,for sunshine duration,2293.12?2732.42h/a,for altitude 1727?2896m,soil types mainly for Calcisol sand Gypsisols and vegetation types mainly for coniferous forest,artificial vegetation and meadow.5.Total power of agricultural machinery,Effective area of irrigation,Per capita GDP,Gross output value of animal husbandry,Number of livestock and Total yield of grain had the greatest impact on vegetation and was the main human factors affecting vegetation changes;followed by Per capita net income of rural households,Per capita yield of grain,Gross output value of farming and Consumption of chemical fertilizers;the rest of the human factors had little effect.Thus,Total power of agricultural machinery,Effective area of irrigation,Per capita GDP,Gross output value of animal husbandry,Number of livestock,Total yield of grain,Per capita net income of rural households,Per capita yield of grain,Gross output value of farming and Consumption of chemical fertilizers can be the human indicators affecting the vegetation coverage.6.Every human indicator has its own appropriate range,among them,for Total power of agricultural machinery 1169811.83?1940003.63 KW,for Effective area of irrigation 425.99?622.33 kilo hectares,for Per capita GDP 2965.86?8124.67 yuan,for Gross output value of animal husbandry 31.42?44.86 hundred million,for Number of livestock 636.51?1222.34 ten thousand,for Total yield of grain 101.14?196.76 ten thousand tons,for Per capita net income of rural households 2113.73?2573.25 yuan,for Per capita yield of grain 5199.51?7454.09 tons,for Gross output value of farming 5.89?13.04 hundred million and for Consumption of chemical fertilizers 1.31?1.85 ten thousand tons.7.The interactions of natural indicators showed that natural factors overlay greatly enhanced the effects of individual factor on the vegetation.Soil types and altitude,vegetation types and altitude,temperature and sunshine duration even had nonlinear cooperative effect.Therefore,sunshine duration and elevation can be used as auxiliary factors in vegetation monitoring.8.The interaction of human indicators showed that human factors overlay greatly enhanced their separate effects on the vegetation.Nonlinear cooperative effect exists among Per capita net income of rural households and Total yield of grain,and Total power of agricultural machinery,and Per capita GDP,and Gross output value of animal husbandry,and Number of livestock;equally,nonlinear cooperative effect also exists among Per capita yield of grain and Total power of agricultural machinery,and Effective area of irrigation,and Gross output value of animal husbandry,and Number of livestock,and Total yield of grain;and Gross output value of farming and Effective area of irrigation,and Total power of agricultural machinery,and Per capita GDP,and Gross output value of animal husbandry,and Total yield of grain also showed nonlinear cooperative effect;Consumption of chemical fertilizers and Effective area of irrigation,and Gross output value of farming,and Gross output value of animal husbandry,and Per capita GDP,and Number of livestock also showed nonlinear cooperative effect.Therefore,Per capita disposable income of urban households,Per capita yield of grain,Gross output value of farming and Consumption of chemical fertilizers can be used as auxiliary factors for the study of human factors influence on vegetation.9.The interactions of natural indicators and human indicators showed that PD value of precipitation,soil type and vegetation type of the natural factors interacting with each of human factors was large and natural factors and human indicators overlay greatly enhanced the effects of individual factor on the vegetation. |
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