Study On Climate Change And NDVI Response Of Chongqing In Recent 20 Years

This paper chooses Chongqing as the research object,and uses the temperatures and precipitation data,MODIS/NDVI data set and DEM image data from 2000 to 2017 in Chongqing.Using the unary linear simulation,partial correlation analysis,residual analysis and R/S analysis method,from the aspect of time and space,respectively discusses the climate and NDVI changes,driving factors and NDVI change trend is sustainable aspects of content in Chongqing from 2000 to 2017.The study finds that:(1)From 2000 to 2017,the annual average temperature shows a trend of a modest rise in Chongqing,which warms up to 0.4?.Only the winter average temperature decreased obviously.Both annual and seasonal average temperature show a trend of decreasing from west to east to north and south.From 2000 to 2017,the average annual precipitation in Chongqing shows an obvious upward trend with an increase of 118 mm.In terms of seasons,the precipitation increases obviously in spring and autumn,staying stable in summer and decreases obviously in winter.From the perspective of space,annual precipitation decreases from southeast to northwest,and the average precipitation in each season is somewhat different.(2)Spatial distribution and variation trend of vegetation.The average annual NDVI in Chongqing reaches 0.7 for many years,among which the highest NDVI reached 0.75 in summer and the improved vegetation area reached 89%.From the regional perspective,the NDVI value in southeast Chongqing is the highest which reaches 0.71 and the vegetation improvement area reaches 95%.The lowest NDVI value in the main urban area is 0.65,and the vegetation improvement area reachs 51%.The fluctuation range of vegetation in Chongqing during the study period is small,and 98.9% of the areas shows low fluctuation and stable change trend.Vegetation fluctuation is obvious in the main urban area,and 18% of the areas shows a high fluctuation state.(3)From the driving force factor,the partial correlation coefficient of NDVI is 0.008 and the value of temperature and precipitation is 0.0028.The value is small,and the complex correlation coefficient between NDVI and temperature and precipitation is relatively high,which is 0.037.Over the years,the effect of human activities on NDVI in Chongqing has shown a trend from negative to positive.Except the main city and some urban centers in western Chongqing show a negative effect,the rest are mainly positive.(4)From the perspective of the continuity of NDVI change trend,this paper uses R/S analysis method to predict the future change trend of vegetation in Chongqing.The Hurst index of Chongqing is 0.53 after calculation,indicating that the future change trend of NDVI in Chongqing is sustainable and mainly shows the trend is sustainable and stable,which accounts for 37% of the area.From the perspective of space,Chongqing's NDVI shows a trend of continuous or slight degradation in urban,industrial and agricultural areas,and the vegetation protection and restoration in this area should be strengthened in the subsequent ecological environmental protection.