Analysing global climatic change and its impact on fruit tree phenology using ClimaTree tool: Example of Anna apple tree under Tunisian conditions

Fruit trees development depends on climatic conditions, and the temperature regime on phenological phases. This study aims at (i) developing a software “Climatree®” to predict the occurrence of the phenological stages of tree fruits, (ii) analyzing the trend of chilling and heat accumulation during the last twenty years, (iii) estimating rest completion, flowering and ripening dates under real weather conditions. In particular, we focus on the study of an early apple cultivar “Anna”, for its chilling requirements for breaking dormancy and heat requirements for flowering and fruit maturing, and (iv) analyzing the effects of global warming on the timing of these phenological stages. The validity of the climate change hypothesis was tested using a climate database. Results pointed out a linear decrease in chilling accumulation during autumn and winter, and a linear increase in heat accumulation during spring. This was observed for all the studied sites. This might confirm the climatic warming in the Mediterranean area during the past years. The theoretical impact of the predicted climate warming on fruit trees phenology is also proposed by using four simple scenarios (theorical increase of both daily maximum-minimum historical temperatures by 0.5, 1.0, 1.5 and 2°C, respectively). For this purpose, the case of an early budbreak apple cultivar “Anna” was chosen. Based on the cultivar´s chilling and heat requirements, the software simulations indicated a delay in the bud burst date, and a shortening in time of flowering and ripening.