Spring Warming Impact on the Reproductive and Vegetative Phenology and Biomass of Two Olive Cultivars in Argentina

Olive cultivation in warm regions is likely to be vulnerable to the expected temperature increases associated with climate change. The objectives of this study were to evaluate the effects of experimental warming at the end of late winter and spring on the timing of phenological stages, the duration of developmental periods, plant growth, and biomass production. The experiment was conducted in control (T0) and warmed (+4 °C, T+) open-top chambers (OTCs) during 2018 and 2019 using two olive cultivars ('Arbequina', 'Coratina') in northwest Argentina. Warming generally led to statistically significant earlier inflorescence development, flowering, fruit set, and pit hardening, with the responses being more pronounced as the spring progressed. Earlier vegetative bud opening occurred due to warming in 2018, but not in 2019. Additionally, no differences in shoot elongation or aboveground biomass were observed due to warming at the end of spring in either 2018 or 2019. Fruit set was reduced by warming, particularly in 'Coratina'. Overall, the experimental results show that reproductive development is more sensitive to warming than vegetative growth in young olive trees. Further studies should be conducted in a larger number of olive cultivars and regions to improve our ability to predict responses to global warming.