Historical phenological responses in apple tree to contrasting warming contexts may clarify future crucial responses in Europe

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Historical phenological responses in apple to contrasting warming contexts may clarify future crucial responses in Europe

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresPhenological responses to warming in temperate fruit trees have rarely been investigated in contrasting warming contexts. This framework is appropriate for highlighting varying responses that would combine chill accumulation declines and heat accumulation increases. A comprehensive overview of historical responses might clarify crucial future responses in the warmest European regions. To examine this issue, a dataset was constituted in apple from flowering dates collected for main BBCH stages in contrasting temperate regions of Western Europe and in different mild regions (Northern Morocco, Southern Brazil). Multiple change-point models were applied to series of flowering date, flowering duration and temperature, aiming to statistically analyse both flowering responses and temperature changes. Modelling of flowering date was used to understand the determinisms of warming responses. In addition, regional differences in dormancy dynamic were characterized by forcing tests. Statistical analysis provided an overview of flowering date responses at global scale, highlighting flowering advances, mainly in Europe and Morocco, but also stationary flowering date series in Brazilian and French Mediterranean regions. Modelling analysis supported the notion that flowering advances are due to heat accumulation increases, explained by marked warming during ecodormancy. Later dormancy releases due to chill declines were also supported in Europe and may explain, in long term, stationary flowering dates in the French Mediterranean region. While the flowering duration series were stationary whatever the region, the flowering duration was far longer in Moroccan and Brazilian regions compared to European. This was linked to contrasting differences in dormancy dynamic observed between these mild and temperate regions. Dormancy release was inadequate in mild due to poor chill accumulation, leading to extended flowering durations. Since later dormancy releases would already have significant impacts on flowering date in Europe, new crucial warming responses, such as extended flowering durations, could be experienced especially in Mediterranean regions in near future

Quels risques peuvent produire les changements climatiques sur la phénologie des arbres fruitiers en Méditerranée? Un diagnostic durant un passé récent comme feuille de route stratégique pour une arboriculture durable en avenir

International audienceL’objectif de ce travail est de comprendre l'impact du changement climatique, en particulier l’augmentation des températures, sur la phénologie des arbres fruitiers ayant une valeur socio-économique importante dans la méditerranée (Meknès et Tassaout au Maroc, Nîmes et Montpellier en France et Forli en Italie). Trois espèces ont été étudiées : l’olivier, le pommier et l'amandier. Trois approches méthodologiques complémentaires ont effectuées: statistique, expérimentale et modélisation. L’analyse des données de température a montré un réchauffement climatique significatif dans les trois régions pendant la période rassemblant les mois octobre-mai. Ce réchauffement a engendré une précocité de floraison chez les arbres fruitiers, avec une sensibilité remarquable chez l’olivier et le pommier. Le processus physiologique propre à chaque espèce pendant à la fois la période de dormance et de croissance explique, en partie, les différences régionales observées dans les dates de floraison entre sites (Maroc et France) et espèces (pommier et amandier). Les tendances des stades phénologiques simulées par modélisation chez le pommier sont en concordance avec celles observées au champ. Cette approche (modélisation) est un outil puissant pour la prévision phénologique dans le contexte des changements climatiques et il peut servir dans les processus de la décision managériale

Global warming impact on floral phenology of fruit trees species in Mediterranean region

IUMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresThis study was carried out in three geographically contrasting countries of the Mediterranean region. Itaims to understand the impact of climate change, particularly the temperature increases, on phenologicalstage of three taxonomically different species (early and late-spring-flowering species). Three species,namely olive (Olea europaea), apple (Malus domestica Borkh.) and almond (Prunus dulcis (Mill.)) wereinvestigated to highlight the phenological behavior of one species at different locations and differentspecies at one location. Climatic and phenological data were collected from Morocco, France and Italyover the last 40 years. Analysis of data on temperature showed a strong warming in the northern locations(coldest areas), particularly in Nîmes, compared to the southern ones (warmer locations) during theperiod October to May. The marked spring warming in all locations since the end of 1980s in France(the beginning of 1990s in Italy and Morocco) resulted in blooming earliness, with regional patterns interms of impact. The late-spring-flowering species (olive and apple) showed a remarkable sensitivity tocontinuous warming in different areas. No flowering earliness was observed in early-spring-floweringspecies (almond), due to the stability of mean temperature during February. Thus, a strong control ofmean temperature during the forcing period on flowering earliness of apple was found in all areas.Physiological processes (dormancy and dormancy release) of trees during the dormant and growth periodexplain, in part, the regional differences observed in flowering dates among sites and species. Overall, thepronounced warming in the southern France reflects a relative trend toward aridity of climate at this site,and consequently some vulnerability of fruit trees. As result, the process of flowering in a high latitudelocations (northern areas) in the future can be represented by that in a low latitude locations at present(southern areas), particularly for apple

Contrasted Warning patterns in both hemispheres result in divergent blooming trends for apple.

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Response of almond flowering and dormancy to Mediterranean temperature conditions in the context of adaptation to climate variations

International audienceDetermining the flowering and the dormancy phases in fruit trees is a crucial process because of their substantial role in some agricultural practices and crop managements. However, few of these studies were conducted on almond flowering and dormancy, particularly in mild climate areas. This study aimed to simulate the dormancy phases, closely involved in the determination of flowering time of almond species in response to temperature variations. To reach this objective, Partial Least Squares analysis was used. In this regard, climatic and flowering data were collected from Ain Taoudjate in Morocco during the period from 1974 to 2014. In fact, a significant temperature increase was highlighted, inducing a decrease in amounts of chill during the studied period. Using Partial Least Squares analysis, a good fit of data was obtained, particularly using mean and maximal temperatures. Two relevant periods controlling the flowering process were highlighted in Tuono cultivar, in concordance with the sequential model in prediction of flowering times. The first long chilling period started from October 01st to January 11th. During this period, temperatures correlated positively with flowering dates, inducing consequently a delayed flowering dates because of low and slow accumulation of chilling requirements. However, the second short forcing period extended from January 18th to March 09th, during which flowering dates were negatively correlated with temperatures. In fact, the accumulation of certain threshold of Growing Degree Hours and Chill Portions during the two periods respectively could delay flowering, particularly in the context of chilling privation in the coming future, causing a serious problem for fruit trees. Significantly, temperatures during the chilling period seemed to affect effectively the flowering dates of almond than temperatures during the forcing period. In this investigation, we demonstrated that Partial Least Squares showed a good fit in explanation of the flowering process and can be used for prediction of dormancy phases and flowering process

Identification de différents modes de dormance chez un arbre fruitier suivant les conditions environnementales et le génotype cultivé : quel enseignement en terme d'adaptation ?

Des tests de forçage durant la dormance ont été appliqués à des bourgeons végétatifs et floraux de pommier dans deux sites à climats doux (Nord du Maroc, Sud du Brésil) et un site à climat tempéré (Sud de la France). Des tests similaires ont été conduits pour l’amandier dans le Nord du Maroc. Des différences d’intensité et de cinétique de dormance ont été identifiées en lien avec les différences régionales de satisfaction des besoins en froid et différents niveaux de besoins des génotypes étudiés. La diversité observée des modes de dormance suggère que des génotypes adaptés aux climats doux (amandiers, pommiers à faibles besoins en froid) se caractérisent par une aptitude des bourgeons végétatifs à demeurer dans un état de faible dormance et une aptitude des ébauches florales à croître rapidement, garantissant l’absence d’anomalies phénologiques ultérieures à la feuillaison et la floraison

Differentiated dynamics of bud dormancy and growth in temperate fruit trees relating to bud phenology adaptation, the case of apple and almond trees

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresInternational audienceFew studies have focused on the characterization of bud dormancy and growth dynamics for temperate fruit species in temperate and mild cropping areas, although this is an appropriate framework to anticipate phenology adaptation facing future warming contexts which would potentially combine chill declines and heat increases. To examine this issue, two experimental approaches and field observations were used for high- and low-chill apple cultivars in temperate climate of southern France and in mild climates of northern Morocco and southern Brazil. Low-chill almond cultivars offered an additional relevant plant material for comparison with apple in northern Morocco. Divergent patterns of dormancy and growth dynamics were clearly found in apple tree between southern France and southern Brazil. Divergences were less pronounced between France and Morocco. A global view outlined main differences in the dormancy chronology and intensity, the transition between endordormancy and ecodormancy and the duration of ecodormancy. A key role of bud rehydration in the transition period was shown. High-chill cultivars would be submitted in mild conditions to heterogeneous rehydration capacities linked to insufficient chill fulfillment and excessive forcing linked to high temperatures. This would favor bud competitions and consequently excessive flowering durations and weak flowering. Low chilling requirements in apple and almond would conversely confer biological capacities to tolerate superficial dormancy and abrupt transition from endordormancy to ecodormancy without important heterogeneous rehydration states within buds. It may also assume that low-chill cultivars can also tolerate high temperatures during ecodormancy as well as extended flowering durations