Spatiotemporal variations in leaf-out phenology of typical European tree species and their responses to climate...

Over the past decades, global warming significantly affected the spring phenology of plants. Many studies have reported the temporal and spatial patterns of spring phenological changes in China, but relatively less is known for that in Europe, which is also located in the temperate area of the Northern Hemisphere. To facilitate the regional comparison of phenological change and understand its response to climate change, we used the data of first leaf date (FLD) in Europe (1980-2014) and the corresponding meteorological data to examine the spatiotemporal variations in leaf-out phenology of four typical tree species (Aesculus hippocastanum, Betula pendula, Fagus sylvatica, and Quercus robur), and to identify the major climatic factors driving such variations. The results showed that the FLD of the four species in the study area advanced by 3.3-7.5 d·10 a^-1 during 1980-2014. The FLD was delayed at a rate of 2.03-3.19 d per degree of latitude from south to north, of 0.19-0.80 d per degree of longitude from west to East (except for Fagus sylvatica), of 2.25-3.44 d·100 m^-1 from low to high elevation. The advances in the FLD were mainly attributed to the increases of temperature in spring and the increases of precipitation in spring and winter. The rise of temperature in autumn and winter would delay FLD.