Lowering phenology and dormancy dynamics of apple tree in contrasting climatic conditions: a case study of phenology modeling in the climate warming context

摘要

Weather patterns have changed globally in recent decades causing seriousconsequences on the development of several plant species. The intensification ofphenological advances in the northern hemisphere has raised interest in theunderstanding of dormancy physiology in temperate species when subjected towarming regimes. The purpose of this study was to compare regional patterns oftemperature on the flowering of apple tree cultivars grown under contrasting climates,using an extensive database of temperature and phenology records. Thus, it waspossible to understand how temperature controls the flowering process and identifythe areas most vulnerable to warming. Historical temperature series collected forWestern Europe (cold winter), Morocco and Southern Brazil (warm winter) were used.Historical dates of two flowering stages and the time between them were analyzed. Allareas in Western Europe experienced warming in the spring, whereas a slight warmingof winter was found in the mild areas. The observed advancement of blooming datesand the short blooming time were linked to spring temperature increase in WesternEurope, with the southern region being more vulnerable to future warming. In Moroccoand Southern Brazil minimal warming was found in recent decades but winter wasmost affected. Weak phenological changes and long flowering periods wereassociated with winter temperatures. Phenology patterns and intermediatetemperatures were observed in Morocco. Moreover, an additional study wasconducted in Brazil and France to understand the mechanism of dormancy in appletrees, the intrinsic factors that controls it, and to analyze the regional and varietalvariability. The kinetics of dormancy in vegetative buds was determined by a "One-budcutting test" and in floral buds by "Tabuenca's test." Vegetative buds showedfluctuating dormancy during autumn-winter-spring in France, which was deeper inwinter. In Brazil, the vegetative buds showed weak variations and shallow depth in theequivalent period. The significant increase in fresh and dry weight of flower primordiacharacterized the transitional phase between endo- and ecodormancy. However,ecodormancy establishment was related to the significant increase in dry weight offloral primordia and their ability to rehydrate. The transition between these phases wasfast in Brazil and slower in France. Sequential models, able to estimate annualblooming dates in both hemispheres were selected from historical temperature andphenology data. Two models were validated to estimate the stages BBCH 61(NHGoldenF1) and BBCH 65 (NHGoldenF2) of Golden Delicious in Western Europe.These models showed high accuracy and greater efficiency in relation to thermalmodels. Considering a CPR scenario of intense increase in temperature by the end ofthis century, there was estimated a trend to extend the period of chill accumulation,especially in Nîmes, and advance dates for flowering in Angers, by the end of thiscentury, according the two NH models. Under both scenarios and locations, there wasa significant reduction in the ecodormancy phase, with the lowest values recorded atNîmes. The projected changes in temperature in the mediterranean region of Europecan extend the flowering period, resulting in physiologic disturbances as today in mildclimate. Other concepts of models and/or the inclusion of multiple factors in the modelshould be considered in the near future, considering that warming in Europe maycompromise the applicability of the sequential models, as observed currently insouthern Brazil.