Chilling and heat requirements for woody taxa in Tétouan (NW Morocco)

Impact of climate change affects chilling and heat accumulation that phenological development of plant needs, air temperature being determinant for flowering, pollination and fruit production, but few knowledges are available in the winter and spring climate of Tétouan. The physiological mechanisms of the reproductive cycle that controls pollen emission are related with temperature, and different environmental factors regulate strongly the reproductive phases of the plant’s life cycle. However, from an empirical point of view, the alternance between endodormancy and ecodormancy is not well detectable. Our work focuses on determining the heat accumulation periods associated with the thermal balance needed to fulfill the chilling and heat required for budbreak and bloom timing. To evaluate Morus, Pistacia, Quercus and Olea response to changes in chill and heat accumulation rates, the Dynamic Model and the Growing Degree-Days Method were used. Regression analyses identified the chilling and forcing periods for these taxa. Over the past 12 years, chill accumulation during tree dormancy increased significantly for most of woody taxa studied, while heat accumulation decreased not significantly for all taxa. Heat accumulation was the main driver of bloom timing, with effects of variation in chill accumulation.