Research On Vegetation Phenology Under The Combined Influence Of Urbanization And Climate Change

Urbanization is the main factor of environmental change caused by human beings.Changes in the hydrothermal characteristics and atmospheric composition of the underlying surface in cities lead to regional climate change,which in turn affects the phenology of vegetation.Vegetation phenology is a sensor of climate and environmental change.The study of urban vegetation phenology is conducive to understanding the impacts of climate change and urbanization on ecosystem.In this study,the Beijing-Tianjin-Tangshan region was selected as the research area.Base on the MOD13Q1 vegetation index products from 2001 to 2019,the phenological parameters(SOS,EOS and LOS)of vegetation in the study area were extracted to reveal the spatiotemporal variation characteristics,and the effects of urbanization and climate factors on vegetation phenology also studied.The main conclusions are as follows:(1)In the Beijing-Tianjin-Tangshan region,the SOS was advanced,the EOS was delayed and the LOS was extended.The phenological changes of vegetation were more obvious in the suburbs of Beijing and Tianjin,while Tangshan,in contrast,was more significant in urban areas.(2)The vegetation phenological period showed a clear gradient phenomenon along the urban-suburban direction.As distance from urban areas increases,SOS got later,EOS got earlier,and LOS got shorter,and the farther away from the urban area,the smaller the magnitude of vegetation phenological period changed.Compared with Tangshan,the correlation between vegetation phenology and urbanization factors was stronger in Beijing and Tianjin.(3)Vegetation phenology in both urban and suburban areas was influenced by urbanization factors.The vegetation phenology changes in suburbs of Beijing and Tianjin were more influenced by urbanization factors,but in Tangshan,urban vegetation phenology was more affected by urbanization factors.Compared with Tangshan,the correlation between vegetation phenology and urbanization factors was stronger in Beijing and Tianjin.(4)Climate was an important factor affecting vegetation phenology.The SOS and LOS in urban and suburban areas were mainly affected by temperature,and the vegetation in urban areas was more affected.The climatic factors that affect LOS differed from urban to suburban areas.(5)Vegetation phenology in urban and suburban areas of Beijing,Tianjin and Tangshan was less affected by urbanization or climate factors singularly.Only SOS and EOS in Beijing urban area and vegetation phenology in Tangshan suburb were affected by urbanization or climate factors.Most of the vegetation phenology was affected by both urbanization and climate factors,and the vegetation phenology was more affected by climate factors in urban areas,and vice versa in suburban areas.