Temperature during a particular period prior to spring leaf-out, the temperature-relevant period (TRP), is a strong determinant of the leaf-out date in temperate-zone trees. Climatic warming has substantially advanced leaf-out dates in temperate biomes worldwide, but its effect on the beginning and length of the TRP has not yet been explored, despite its direct relevance for phenology modeling. Using 1,551 species-site combinations of long-term (1951-2016) in situ observations on six tree species (namely, Aesculus hippocastanum, Alnus glutinosa, Betula pendula, Fagus sylvatica, Fraxinus excelsior, and Quercus robur) in central Europe, we found that the advancing leaf-out was accompanied by a shortening of the TRP. On average across all species and sites, the length of the TRP significantly decreased by 23% (p < .05), from 60 +/- 4 days during 1951-1965 to 47 +/- 4 days during 2002-2016. Importantly, the average start date of the TRP did not vary significantly over the study period (March 2-5, DOY = 61-64), which could be explained by sufficient chilling over the study period in the regions considered. The advanced leaf-out date with unchanged beginning of the TRP can be explained by the faster accumulation of the required heat due to climatic warming, which overcompensated for the retarding effect of shortening daylength on bud development. This study shows that climate warming has not yet affected the mean TRP starting date in the study region, implying that phenology modules in global land surface models might be reliable assuming a fixed TRP starting date at least for the temperate central Europe. Field warming experiments do, however, remain necessary to test to what extent the length of TRP will continue to shorten and whether the starting date will remain stable under future climate conditions.
1.Beijing Normal Univ, Coll Water Sci, Beijing 100875, Peoples R China 2.Univ Antwerp, Dept Biol, Antwerp, Belgium 3.Swiss Fed Inst Forest Snow & Landscape Res WSL, SwissForestLab, Birmensdorf, Switzerland 4.ETH Zurich Swiss Fed Inst Technol, Inst Integrat Biol, Zurich, Switzerland 5.CREAF, Barcelona, Catalonia, Spain 6.CSIC, Global Ecol Unit CREAF CSIC UAB, Barcelona, Catalonia, Spain 7.Peking Univ, Coll Urban & Environm Sci, Sinofrench Inst Earth Syst Sci, Beijing, Peoples R China 8.Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Alpine Ecol & Biodivers, Beijing, Peoples R China 9.Chinese Acad Sci, Ctr Excellence Tibetan Earth Sci, Beijing, Peoples R China
Recommended Citation:
Fu, Yongshuo H.,Geng, Xiaojun,Hao, Fanghua,et al. Shortened temperature-relevant period of spring leaf-out in temperate-zone trees[J]. GLOBAL CHANGE BIOLOGY,2019-01-01