Spatial and Temporal Evolution of Vegetation and Response to Droughts in the Middle and Lower Reaches of the Yangtze River based on Multi-source Remote Sensing Data
This study analyzed the spatial and temporal evolution of vegetation cover in the middle and lower reaches of the Yangtze River Basin from 2000 to 2021.The data used included Normalised Difference Vegetation Index(NDVI),Enhanced Vegetation Index(EVI),Gross Primary Productivity(GPP)and Global Orbiting Carbon Observatory-2 Solar-Induced Chlorophyll Fluorescence(GOSIF)products inverted from Solar Induced Chlorophyll Fluorescence(SIF).The response of vegetation cover under drought conditions was further analysed by combining with the Standardized Precipitation Evapotranspiration Index(SPEI).The main conclusions were as follows:(1)Temporally,the average annual NDVI,EVI,GOSIF and GPP in the study area showed an overall significant increasing trend,with the increasing rates of 0.002 9 a-1,0.002 4 a-1,0.001 8 W·m-2·μm-1·sr-1·a-1 and 8.327 4 gC·m-2·a-1(P＜0.05);The monthly NDVI,EVI,GOSIF and GPP showed obvious intra-annual variations,with their maximum values occurring in July or August each year.(2)Spatially,NDVI,EVI,GOSIF and GPP in the study area showed a similar spatial distribution pattern,with the high-value areas mainly distributed in the southwestern part of Hunan Province,the western part of Hubei Province and Jiangxi Province,and the low value areas mainly distributed in the eastern part of the basin,such as Shanghai,Jiangsu,and Zhejiang.The percentage of areas with significantly decreasing trends were only 3.00％,3.25％,2.19％and 1.00％(P＜0.05).(3)As the severity of drought increases(from mild to severe drought),the average decrease in the change rates of NDVI,EVI,GOSIF,and GPP from April to September showed an increasing trend.NDVI,EVI,GOSIF and GPP decreased from-2.45％,-3.87％,-4.77％and 0.58％in mild drought to-7.26％,-8.57％,-12.59％and-7.87％in the severe drought,respectively.The average values of GOSIF rate of change from April to September under different drought levels demonstrated a greater decrease than those of NDVI,EVI and GPP,indicating that the response of GOSIF to drought events was more sensitive.
vegetation indexGPPGOSIFspatial and temporal evolutionmiddle and lower Yangtze River Basin
NETL
NSTL
万方数据
