Varaiation Of Vegetation And Its Response To Extreme Climate In Shenzhen

Shenzhen is a typical area of rapid urbanization in China.It experienced population expansion and land use changes,so the eco-environment has been greatly affected.Vegetation as an important part of the ecological environment has received extensive attention.In the context of global climate change,extreme climate events occur more frequently and have a certain degree of impact on vegetation coverage.In this view,the characteristics of spatio-temporal changes in vegetation cover and the spatio-temporal changes of extreme climate in Shenzhen were studied,and the response of vegetation changes to extreme climatic events was further explored,which would be conducive to the promotion of regional eco-environmental protection and the preservation of ecological construction.Based on the landsat TM/OLI data and MODIS NDVI data from 1986 to 2015,this paper obtained the spatio-temporal characteristics of NDVI in Shenzhen.Based on the daily temperature and precipitation data from the Shenzhen meteorological site,the extreme temperature index and extreme precipitation index were calculated.The temporal and spatial differences were analyzed.Finally,the response characteristics of NDVI to extreme climate events were explored.Research indicates the following:(1)The vegetation in Shenzhen City was affected by urbanization from 1986 to 2015,showing a trend of decreasing first and then increasing.The vegetation changes affected by urbanization also have different performances in different administrative regions.(2)During the period from 1953 to 2015 in Shenzhen,the extreme temperature index showed an upward trend and the climate became warmer;the frequency and intensity of extreme precipitation decreased,but the duration increased.In terms of spatial differences,the temperature is mainly due to the small temperature difference between Dapeng and Yantian,while the Pingshan and Longgang districts have large temperature differences;the precipitation shows a decreasing pattern from east to west.(3)Response of NDVI to extreme climate index.On the interannual scale,the extreme air warmth index and extreme value index are positively correlated with NDVI overall;the impact of precipitation index on NDVI is greater than that of temperature index.On the monthly scale,the extreme temperature index has a greater impact on NDVI and has a stronger spatial disparity,basically showing an increasing influence from south to north;the extreme precipitation index has less influence on NDVI than temperature index.In the spatial distribution,the influence gradually decreases from south to north.Considering the time-delay effect of climate change on vegetation,the correlation coefficient of most indexes to NDVI is obviously increased,and the spatial difference is changed.The correlation of temperature index shows the radial increase from downtown to the periphery;The spatial distribution of the exponential correlation with extreme precipitation has changed little.