Vegetation Cover Change And It's Sensitivity To Climate In Xinjiang

Xinjiang is located in the arid and semi-arid climate region of eurasia,rare vegetation,serious soil erosion,ecological environment is extremely fragile,desertification has led to the reduction of land area,the continuous increase of mobile dune,the decline of land productivity and so on.With 2002-2015 as the research time,taking Xinjiang area as the study area,year,season and month for research scale,using 52 meteorological data,MODIS NDVI data and social economic statistical data and field observation data,The spatial and temporal characteristics and distribution of vegetation cover were revealed by means of MVC,regression analysis,trend analysis and correlation analysis,revealed the temporal and spatial characteristics of vegetation cover change and its distribution,Based on the multi factor analysis,simulate the spatial distribution information of precipitation and air temperature and analysis it's change trend of time series by the method of Stepwise synthesis.From the perspective of spatial and temporal correlation,Using the spatial econometric analysis and model analysis the relationship between vegetation and climatic factors and explain the cause of vegetation cover change in Xinjiang area.Results show:(1)The spatial distribution pattern of vegetation cover in Xinjiang is increasing from southwest to northeast in NDVI,which is the same as the distribution of precipitation.The distribution area of bare soil area was the largest,and the sparse vegetation area,the less vegetation area,the moderate vegetation area,the dense vegetation area,the dense planting area and the dense vegetation area were reduced.From the point of view of time,NDVI change rate 4-6 months >2-4 months >6-8 months.The linear trend of average vegetation coverage in spring,summer and autumn was positive,the average vegetation coverage was lowest in spring,followed by autumn and The highest vegetation coverage in summer,at seasonal variation.At the year scale,NDVI is the overall upward trend,from 2002 to 2015,NDVI decreased significantly during 2005 and 2009,and reached the lowest NDVI at 2009.(2)Studied the changing tendency of annual maximum NDVI,Vegetation coverage is increasing in most areas in 14 years.The trend rate of NDVI was-0.077-0.076,94.99% NDVI remain unchanged(-0.01<Slope<0.01),The range of NDVI degradation(Slope <-0.02)accounted for 10.35%,NDVI improvement range(Slope>0.02)accounted for 4.27%.(3)Geographical distribution trend of Average precipitation is “North More and South Less,West More and East Less”,decreasing from northwest to Southeast,most of the regional precipitation is rare(less than 200mm),and the annual precipitation in Xinjiang is not significantly reduced.There is obvious seasonal difference in precipitation in Xinjiang,summer>autumn>spring;In Xinjiang area,the maximum precipitation was in June and in July,followed by the year of August,May and September.The average annual temperature of in the Xinjiang area was between-3.5? and 15.7?.The average annual temperature is 9.36?.The geographical distribution characteristics of the total is the South than in the north,the East West High low,decreasing from south to north,the annual average temperature in Xinjiang showed a significant growth trend.The seasonal temperature distribution is uneven in Xinjiang area,the highest in summer,followed by spring,autumn,In winter,the average temperature is the lowest,cold and long,and the average temperature is below-10?.(4)There was a positive correlation between annual maximum NDVI value and annual precipitation.On the interannual scale,the change of annual precipitation is the main factor that leads to the change of vegetation cover.The annual mean temperature had no significant positive correlation with the annual maximum NDVI,indicating that the vegetation coverage was also increased with the increase of temperature,but the effect was small.