Sequential modeling to understand and predict differentiated flowering time responses to warming in apple tree in contrasting climatic regions

G Malagi,I Citadin,J.M Legave,A El Yaacoubi,M Bonhomme,I Farrera,J.L Regnard

doi:10.17660/actahortic.2017.1160.28

Abstract

Long-term series of temperature and apple flowering date were set up for seven climate-contrasting locations in Western Europe. A statistical analysis and a sequential modeling approach has been used to understand how global warming impacted dormancy release and flowering time in recent past and will impact in the future. Selected models explained up to 90% of the flowering date variability in Europe. Both the statistical analysis and the modeling of flowering dates supported that flowering advances in European temperate climates were clearly linked to faster fulfillments of heat requirements due to marked spring warming since the end of the 1980s. Delays of dormancy release, linked to chill temperature declines, were likely to also occur especially in the French Mediterranean region, which can explain a stationarity of the flowering date series since the beginning of the 2010s. Predicted changes until the end of the 21st century in Mediterranean region would confirm both a stationarity of flowering time and increasing delays of dormancy release. In addition, historical series of temperature and flowering dates were set up for three mild climate locations (one in Northern Morocco and two in Southern Brazil). While a flowering advance and a spring warming were statistically supported in Morocco, both flowering date and temperature series have generally remained stationary in the Brazilian locations. Finally, differentiated responses of apple tree flowering time were highlighted at the world scale in relation with differentiated warming contexts. Moreover, both sequential models selected from European data and models selected from Moroccan or Brazilian data appeared inadequate to simulate the observed flowering dates in the Moroccan and Brazilian locations. This cast a doubt on the sequential modeling relevance to predict dormancy release and flowering changes in the future warming context of European regions.

Highlights

Long-term series of temperature and apple flowering date were set up for seven climate-contrasting locations in western Europe
Abrupt flowering advances have been observed in all European locations since the end of the 1980s. They were more pronounced in continental than in oceanic locations (10 vs. 6-7 days), while the shortest advance was found in the French Mediterranean location (Nîmes) (Fig. 1). Such advances may be explained by abrupt increases of mean temperatures during the fulfillment of heat requirements (Legave et al, 2013)
When the flowering dates were considered over longer periods (Legave et al, 2015), the statistical analysis outlined a stationarity of flowering date series in Nîmes which would be more probable than a continuous flowering advance as in the other European locations

Summary

Introduction

Delays of dormancy release, linked to chill temperature declines, were likely to occur especially in the French Mediterranean region, which can explain a stationarity of the flowering date series since the beginning of the 2010s. Differentiated responses of apple tree flowering time were highlighted at the world scale in relation with differentiated warming contexts Both sequential models selected from European data and models selected from Moroccan or Brazilian data appeared inadequate to simulate the observed flowering dates in the Moroccan and Brazilian locations. Sequential modeling to understand and predict differentiated flowering time responses to warming in apple tree in contrasting climatic regions. We aimed to answer the following key questions: (1) Are flowering time changes differentiated over a large geographic cropping area? (2) How are flowering and temperature changes linked? (3) Is the sequential chill-growth model suitable for projection analyses?

Objectives

Methods

Results

Discussion

Conclusion