Spatiotemporal Characteristics Of Vegetation Index And Its Relationship With Climate Factors In Xinjiang From 2000 To 2018

The fragile ecological environment in Xinjiang is an important factor restricting the regional economic development.In the "One belt,one road" initiative,Xinjiang is the core area of the Silk Road,and its sustainability is the premise of local social and economic development.Based on the MODIS NDVI from 2000 to 2018,the measured data of 60 meteorological stations in Xinjiang and World Clim data,this paper analyzes the temporal and spatial variation characteristics of NDVI and climate factors in Xinjiang,and discusses the response of NDVI to climate factors.The results show that:(1)From 2000 to 2018,the overall distribution characteristics of NDVI in the study area were high in the west,low in the East and south,and the area without vegetation coverage accounted for 49.63% of the total area of Xinjiang.The NDVI of vegetation fluctuates little,and there is no significant change in most areas.The average NDVI of four seasons showed an increasing trend,and the annual average increase rate of NDVI was 1.42%/10 a.(2)From 2000 to 2018,more than 77.80% of the areas where the coverage level remains unchanged are mainly non vegetation coverage areas and low vegetation coverage areas,and the area with increased coverage accounts for 15.17%,which mainly changes from non-vegetation coverage to low vegetation coverage,and the area with decreased coverage accounts for 2.98%,which mainly changes from medium vegetation coverage to low vegetation coverage,It shows that the vegetation growth trend in the study area is good from 2000 to 2018.(3)From 2000 to 2018,the relative humidity,the maximum humidity and the minimum humidity have obvious decreasing trend;The dew point temperature,annual average temperature and annual sunshine duration had a slight decreasing trend;Annual maximum temperature,annual minimum temperature and average wind speed showed an increasing trend;The annual precipitation increased significantly.The spatial distribution of temperature is high in the South and low in the north,high in the basin and low in the mountainous area.The temperature distribution is greatly affected by the altitude and topography.The precipitation in the north is more than that in the south,the Ili Valley is the highest,and the hinterland of the Tarim Basin is the lowest.The distribution of seasonal precipitation is uneven,and the abundance of annual precipitation depends on the size of summer precipitation.There was a significant negative correlation between relative humidity and sunshine duration(P < 0.05),between wind speed and sunshine duration(P < 0.05),and between sunshine duration and minimum temperature,maximum relative humidity and minimum relative humidity(P < 0.05).The correlation between maximum relative humidity and annual mean temperature and annual precipitation is low,but there is no significant negative correlation between annual mean temperature and annual precipitation.(4)Precipitation is the most important meteorological factor affecting vegetation growth in Xinjiang.The correlation coefficient between NDVI and precipitation in summer,autumn and winter is stronger than that in the same season.It shows that the response of vegetation growth to precipitation has a certain lag effect.There is a negative correlation between NDVI and temperature in May and August;There is a significant negative correlation between the maximum relative humidity and the annual average NDVI.Among the nine vegetation types in Xinjiang,the grassland with medium and low vegetation coverage is the largest and most widely distributed.