title: Three times greater weight of daytime than of night-time temperature on leaf unfolding phenology in temperate trees.
abstract: The phenology of spring leaf unfolding plays a key role in the structure and functioning of ecosystems. The classical concept of heat requirement (growing degree days) for leaf unfolding was developed hundreds of years ago, but this model does not include the recently reported greater importance of daytime than night-time temperature. A manipulative experiment on daytime vs night-time warming with saplings of three species of temperate deciduous trees was conducted and a Bayesian method was applied to explore the different effects of daytime and night-time temperatures on spring phenology. We found that both daytime and night-time warming significantly advanced leaf unfolding, but the sensitivities to increased daytime and night-time temperatures differed significantly. Trees were most sensitive to daytime warming (7.4 ± 0.9, 4.8 ± 0.3 and 4.8 ± 0.2 d advancement per degree Celsius warming (d °C-1) for birch, oak and beech, respectively) and least sensitive to night-time warming (5.5 ± 0.9, 3.3 ± 0.3 and 2.1 ± 0.9 d °C-1). Interestingly, a Bayesian analysis found that the impact of daytime temperature on leaf unfolding was approximately three times higher than that of night-time temperatures. Night-time global temperature is increasing faster than daytime temperature, so model projections of future spring phenology should incorporate the effects of these different temperatures.
authors.affiliation: Centre of Excellence GCE (Global Change Ecology), Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium. Yongshuo.fu@uantwerpen.be.|Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China. Yongshuo.fu@uantwerpen.be.
authors.forename: Yongshuo H
authors.initials: YH
authors.lastname: Fu
authors.affiliation: Centre of Excellence GCE (Global Change Ecology), Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Centre of Excellence GCE (Global Change Ecology), Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: De Boeck
authors.affiliation: Ecoclimatology, Technische Universität München, 85354, Freising, Germany.|Institute for Advanced Study, Technische Universität München, Lichtenbergstraße 2a, 85748, Garching, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Menzel
authors.affiliation: Centre of Excellence GCE (Global Change Ecology), Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
authors.forename: Ivan
authors.initials: I
authors.lastname: Nijs
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, CEA CNRS UVSQ, Gif-sur-Yvette, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Peaucelle
authors.affiliation: CREAF, Cerdanyola del Vallès, Barcelona, 08193, Catalonia, Spain.|CSIC, Global Ecology Unit CREAF -CSIC-UAB, Cerdanyola del Vallès, Barcelona, 11 08193, Catalonia, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Peñuelas
authors.affiliation: Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.|Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Shilong
authors.initials: S
authors.lastname: Piao
authors.affiliation: Centre of Excellence GCE (Global Change Ecology), Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Janssens
mesh_terms: D029662:Betula / Q000502:physiology; D018533:Biomass; D017753:Ecosystem; D029964:Fagus / Q000502:physiology; D008954:Models, Biological; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology*; D029963:Quercus / Q000502:physiology; D012621:Seasons; D013696:Temperature; D013997:Time Factors; D014197:Trees / Q000502:physiology*
keywords: Bayesian analysis; climatic warming; daytime and night-time warming; deciduous trees; growing degree days (GDDs); growing degree hours (GDHs); leaf phenology; leaf unfolding