Plant Phenology Dynamics Along The Urbanization Gradient And Phenological Responses To Landscape Scales

In this study,phenophases of six plant speciess,i.e.Prunus cerasifera,Broussonetia papyrifera,Metasequoia glyptostroboides,Ginkgo biloba,Platanus hispanica and Salix babylonica located in 19 sample sites distributed along two transects from urban to rural gradient in Shanghai,the most urbanised city of China,were investigated in 2013 to explore how urbanization inflences plant phenology and whether urban landscape patterns affect plant phenophases at different scales using urbanization index calculated from land use data derived from 1-meter resolution aerial photos acquired in 2013 in Shanghai.My main findings are as following:(1)Phenophases of all plant species were delayed with the distance from city center.Bud brust stage of Prunus cerasifera,Broussonetia papyrifera,Metasequoia glyptostroboides,Ginkgo biloba,Platanus hispanica and Salix babylonica,Leaf unfolding of Metasequoia glyptostroboides,Ginkgo biloba and Platanus hispanica,Full leaf unfolding of Prunus cerasifera,Broussonetia papyrifera,Metasequoia glyptostroboides,Ginkgo biloba,Platanus hispanica and Salix babylonica,First-flowering date and Full bloom stage of Prunus cerasifera,Broussonetia papyrifera,Ginkgo biloba,Flower bud appearance of Prunus cerasifera,and inflorescence occurrence of Platanus hispanica were all delayed with distance from city center in a linear relationship(P<0.05 or P<0.001).(2)Phenological dynamic of all plant species showed a shape of "S" over time,namely,bud brust,Leaf unfolding and Flowering speed followed a "slow-fast-slow"rule.The dynamic pattern of plant phenophases for Bud burst of Ginkgo biloba and bloom beginning of Prunus cerasifera along the two transects,leaf unfolding of Platanus hispanica along the east-west transect presented delayed trends along urban-rural gradient.But these trends did not exist for leaf unfolding of Metasequoia glyptostroboides and Salix babylonica,and flowering of Broussonetia papyrifera.(3)The correlation coefficient between urbanization index and each phenophses showed that all 9 phenophses investagated in this study are varied with 8 different buffer width.95.4%of the total phenophses for the six plant species showed a negative correlation with urbanization index indicating that plant phenophases advanced with urbanisation degree,among which 47.6%were advanced significantly(P<0.05 or P<0.001).Only 4.6%phenophases showed positive correlation with urbanization index demonstrated that a few phenophases delayed with urbanisation degree in certain scales,but with no significance.(4)There were response scales of plant phenology to urbanization reflected by correlation coefficients(R value)between plant phenophases and urbanization index at different scales,i.e.,the buffer width.From the 250 meter-width buffer to the 2000 meter-width buffer,the correlation coefficient could be well fitted with scales(P<0.05 or P<0.001)and presented first decease,then to be stable or increase with the buffer width increasing.Overall,it looks that the buffer width between 1000m and 2000m is the response scale of plant phenophases to urbanization degree.