Global warming effects on yield and fruit maturation of olive trees growing under field conditions

Temperature in the Mediterranean Basin, the main area of olive (Olea europaea L.) cultivation, has been projected to rise drastically in the near future threatening olive production. To determine the potential effects of higher temperature on the olive fruiting cycle and vegetative growth, a study with the cultivar 'Picual' has been carried out simulating global warming conditions under field conditions. Temperature-controlled open top chamber (OTC) systems were used to increase the day/night ambient temperature 4 degrees C throughout the complete reproductive cycle of this species. Three years of study have shown that 4 degrees C increase of ambient temperature reduces fruit yield and affects fruit characteristics and maturation processes. Smaller fruits, lower pulp/stone ratio, oil yield and anthocyanin contents were observed. The maturation period was forwarded and extended in trees subjected to wanner temperatures. In addition, the vegetative growth was stimulated by the temperature treatment resulting in trees of bigger size.