Global warming has led to substantially earlier spring leaf-out in temperate-zone deciduous trees. The interactive effects of temperature and daylength underlying this warming response remain unclear. However, they need to be accurately represented by earth system models to improve projections of the carbon and energy balances of temperate forests and the associated feedbacks to the Earth's climate system. We studied the control of leaf-out by daylength and temperature using data from six tree species across 2,377 European phenological network (www.pep725.eu), each with at least 30 years of observations. We found that, in addition to and independent of the known effect of chilling, daylength correlates negatively with the heat requirement for leaf-out in all studied species. In warm springs when leaf-out is early, days are short and the heat requirement is higher than in an average spring, which mitigates the warming-induced advancement of leaf-out and protects the tree against precocious leaf-out and the associated risks of late frosts. In contrast, longer-than-average daylength (in cold springs when leaf-out is late) reduces the heat requirement for leaf-out, ensuring that trees do not leaf-out too late and miss out on large amounts of solar energy. These results provide the first large-scale empirical evidence of a widespread daylength effect on the temperature sensitivity of leaf-out phenology in temperate deciduous trees.
1.Beijing Normal Univ, Coll Water Sci, Beijing Key Lab Urban Hydrol Cycle & Sponge City, Beijing, Peoples R China 2.Univ Antwerp, Dept Biol, Antwerp, Belgium 3.Peking Univ, Coll Urban & Environm Sci, Sino French Inst Earth Syst Sci, Beijing, Peoples R China 4.Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Alpine Ecol & Biodivers, Beijing, Peoples R China 5.Chinese Acad Sci, Ctr Excellence Tibetan Earth Sci, Beijing, Peoples R China 6.WSL, Swiss Fed Inst Forest Snow & Landscape Res, Forest Dynam Unit, Birmensdorf, Switzerland 7.ETH Zurich Swiss Fed Inst Technol, Inst Integrat Biol, Zurich, Switzerland 8.CREAF, Barcelona, Spain 9.UAB, CSIC, Global Ecol Unit CREAF, Barcelona, Spain
Recommended Citation:
Fu, Yongshuo H.,Zhang, Xuan,Piao, Shilong,et al. Daylength helps temperate deciduous trees to leaf-out at the optimal time[J]. GLOBAL CHANGE BIOLOGY,2019-01-01,25(7):2410-2418