Different Types Vegetation Response To Drought And Vegetation Coverage Changes Future Trend In Northern China

Vegetation is an important link between water,atmosphere and soil.Vegetation growing is an important indicator of ecosystem change.Meanwhile,surface vegetation is vulnerable to water deficit.The climate of northern China is mainly arid and semi-arid,with high frequency and serious drought.Therefore,it is very important to analyze the impact of drought to vegetation in northern China.Under the background of global warming,water resource condition will change with climate in the future.In this scenario,it has important significance to understand the characteristics of future vegetation by quantitatively and accurately predict vegetation dynamic change in the future.In this study,precipitation and reference evapotranspiration are employed to describe climate change.The Standardized Precipitation Evapotranspiration Index(SPEI)and Normalized Difference Vegetation Index(NDVI)respectively are employed to describe meteorological drought and vegetation dynamic.We were analyzed the dynamic change characteristics of vegetation from 1982 to 2015,the response of vegetation to meteorological drought in different seasons,and the correlation between vegetation and meteorological elements of precipitation and reference crop evapotranspiration.Based on historical meteorology and vegetation data,the vegetation prediction model was constructed.The model would predict vegetation dynamic changes under RCP 4.5 and 8.5 greenhouse gas emission scenarios in 2020-2100.The vegetation change characteristics was analyzed in the future.The main conclusions are as follows:(1)The results show that the vegetation coverage in northeastern China greatly changed in different season,with higher in summer and lower in winter.The vegetation cover of North China greatly changed in different years;The change of vegetation cover little changed in northwestern China.Human activities had an impact on vegetation change.From 1982 to 2015,there just had 3.21%of the total area of vegetation types had been changed in northern China.(2)In the growing season,the vegetation of cold temperate coniferous forest and deciduous broad-leaved mixed forest sub-region showed negative relationship with meteorological drought,meanwhile,vegetation of warm temperate deciduous broad-leaved forest,temperate grassland and temperate desert sub-region showed positive relationship with meteorological drought.There was a positive correlation between vegetation and precipitation in northern China in spring and summer but had negative correlation in autumn.There was a positive correlation between vegetation and reference crop evapotranspiration in different seasons,with high degree of correlation in spring and summer.(3)There had a negative correlation between forest of high coverage and drought and had weaker negative correlation between grassland,cropland and drought.The region vegetation of high coverage and various vegetation types had strong resistance to drought.(4)The vegetation dynamic prediction model constructed by multiple regression equation,which can accurately predict the vegetation dynamic change.The model evaluation parameters mean values of Coefficient of determination(R~2),Root Mean Square Error(RMSE)and Standard Root Mean Square Error(NRMSE)respectively was 0.77,0.04 and 11.05%.(5)Under RCP 4.5 and 8.5 scenarios,both precipitation,reference evapotranspiration and vegetation cover would increase,the increment of RCP 8.5 more than RCP 4.5.In the future,the vegetation cover of growing general increase in North China,moreover,the increase of vegetation cover in RCP 8.5 scenario was greater than that in RCP 4.5 scenario.The vegetation cover of Northeast Plain and North China Plain would decrease in spring,however,those regions mainly distributed cropland.Therefore,water resource conditions in spring may affect crop yield in the future.In the future,vegetation of cold temperate coniferous forest,deciduous broad-leaved mixed forest and warm temperate deciduous broad-leaved forest sub-region had largely increasing but vegetation of warm temperate deciduous broad-leaved forest,temperate grassland and temperate desert sub-region had little increasing.