title: Differentiated Responses of Apple Tree Floral Phenology to Global Warming in Contrasting Climatic Regions.
abstract: The responses of flowering phenology to temperature increases in temperate fruit trees have rarely been investigated in contrasting climatic regions. This is an appropriate framework for highlighting varying responses to diverse warming contexts, which would potentially combine chill accumulation (CA) declines and heat accumulation (HA) increases. To examine this issue, a data set was constituted in apple tree from flowering dates collected for two phenological stages of three cultivars in seven climate-contrasting temperate regions of Western Europe and in three mild regions, one in Northern Morocco and two in Southern Brazil. Multiple change-point models were applied to flowering date series, as well as to corresponding series of mean temperature during two successive periods, respectively determining for the fulfillment of chill and heat requirements. A new overview in space and time of flowering date changes was provided in apple tree highlighting not only flowering date advances as in previous studies but also stationary flowering date series. At global scale, differentiated flowering time patterns result from varying interactions between contrasting thermal determinisms of flowering dates and contrasting warming contexts. This may explain flowering date advances in most of European regions and in Morocco vs. stationary flowering date series in the Brazilian regions. A notable exception in Europe was found in the French Mediterranean region where the flowering date series was stationary. While the flowering duration series were stationary whatever the region, the flowering durations were far longer in mild regions compared to temperate regions. Our findings suggest a new warming vulnerability in temperate Mediterranean regions, which could shift toward responding more to chill decline and consequently experience late and extended flowering under future warming scenarios.
authors.affiliation: INRA, Unité Mixte de Recherche 1334 Amélioration Génétique et Adaptation des Plantes Méditerranéennes et Tropicales Montpellier, France.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Legave
authors.affiliation: CIRAD, Unité Mixte de Recherche 1334 et Inria, Virtual Plants Montpellier, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Guédon
authors.affiliation: Faculdade de Agronomia, Universidade Federal de Pelotas Pelotas, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Malagi
authors.affiliation: Faculté des Sciences, Université Moulay Ismail Meknès, Morocco.
authors.forename: Adnane
authors.initials: A
authors.lastname: El Yaacoubi
authors.affiliation: Unité Mixte de Recherche 547, INRA et Université Blaise Pascal, PIAF Clermont-Ferrand, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Bonhomme
keywords: chill period; flowering; fruit tree; heat period; multiple change-point models; warming vulnerability