Dependency Relationship between NDVI and SPEI for Spatial-Temporal Variations in the Source Areas of the Yellow River
Under the circumstances of global warming,standardized precipitation evapotranspiration index(SPEI) has become an important index in evaluating drought level.Based on eco-functional zoning,MODIS-NDVI and SPEI data collected in the source region of the Yellow River during 2000—2014,this study discussed the spatial-temporal change characteristics of NDVI and SPEI and their dependency relationship.Results showed:(1)the values of NDVI and SPEI demonstrated a rising trend in general in the period of 2000—2014,and the vegetation coverage turned better and the drought level decreased.(2)Both NDVI and SPEI had approximately similar pattern for spa-tial distribution,with a decrease in the southeast and an increase in the northwest.(3)Precipitation was acting as the main factor regulating vegetation growth and SPEI change.The effect of SPEI on NDVI was stronger in the case of 0.3<NDVI<0.6,whereas it was weaker if NDVI >0.6.(4)NDVI presented a positive relationship with SPEI in most parts of the source region of the Yellow River,especially in the Qinggen river ecological zone and the source region of the Yellow River ecological region where were featured by relatively lower vegetation coverage.However, NDVI showed negatively relationships with SPEI in the Huangnan grassland ecological zone and its surroundings, especially at grassland degradation areas and biodiversity sensitive areas.The decrease in drought level would enable vegetation coverage to increase in the study area and provide favorable conditions for ecological restoration in the region.
Source region of the Yellow RiverSPEINDVISpatial-temporal change
NETL
NSTL
万方数据
维普
