2003-2023年额济纳绿洲植被EVI和物候时空变化特征及其气候响应OA

This study investigated the spatiotemporal dynamic characteristics of vegetation cover and key pheno-logical parameters[start of growing season(SOS);peak of growing season(POS);and end of growing season(EOS)]in the Ejin Oasis and revealed their responses to climate change and groundwater fluctuations.The analy-sis was based on MODIS Enhanced Vegetation Index(EVI)data,meteorological observations,and groundwater level monitoring data from 2000 to 2023.Firstly,the multi-year average EVI during the growing season was only 0.13.EVI and phenological parameters were jointly driven by hydrology and land use.Wetland vegetation exhib-ited a pattern of"early SOS,vigorous growth,and late EOS",while cropland showed an anthropogenically regu-lated pattern characterized by"late SOS,delayed POS,and early EOS",with grassland and forest falling in be-tween.Secondly,from 2000 to 2023,the growing season EVI exhibited a highly significant upward trend(r=0.98,P<0.01),and the POS advanced significantly(r=-0.51,P<0.05),whereas the SOS and EOS showed no sig-nificant trends.Thirdly,EVI exhibited a significant positive correlation with the cumulative temperature from Jan-uary to September(r=0.77,P<0.01),whereas its correlation with precipitation was weak.This is primarily be-cause vegetation in the study area relies on river conveyance and groundwater recharge(a significant correlation exists between groundwater level and EVI).Furthermore,rising spring temperatures promoted an earlier SOS,temperature increases in winter and the early growing season led to an earlier POS,and autumn warming delayed the EOS.Fourthly,POS showed a significant negative correlation with EVI(r=-0.49,P<0.05),indicating that an earlier POS is conducive to enhancing vegetation productivity,whereas other phenological parameters had no sig-nificant impact on EVI.This evidence suggests that in hyperarid regions supported by ecological water convey-ance,vegetation growth is primarily driven by the time-lag and cumulative effects of temperature rather than pre-cipitation limitations,and the advancement of POS is a key phenological indicator for improving vegetation pro-ductivity.This research may provide a scientific basis for evaluating the benefits of ecological water conveyance in the Heihe River Basin and vegetation restoration in arid zones.