Long term analysis on Olive flowering and climatic relationships in central Italy

The study aim was to analyze and interpret long-term trends in temperature and olive reproductive features, including full flowering dates and daily pollen concentrations, in central Italy. A 40-year database (1982–2022) of pollen and temperature records was utilized. Temperature changes significantly affect spring phenology and olive trees, sensitive to climate change, exhibit earlier flowering in response to higher spring temperatures. Although this adaptation may lower pollen levels, benefiting public health, it could negatively impact agricultural yields. Olive trees in the study area demonstrated phenological plasticity, transitioning from rigid to flexible flowering behaviors. They adjusted the Growing Degree Days (GDDs) required for flowering once they reached a threshold of maximum advancement. Until 2004, the trees accumulated similar GDD values. With rising temperatures, earlier flowering occurred at fixed GDD values of 650 and 750. Subsequently, the trees began accumulating higher GDD values, stabilizing the flowering date and preventing further advances. This phenological plasticity allows olive trees to adapt their life cycle and developmental stages to environmental changes such as temperature, light, and water availability. This flexibility helps them survive in changing conditions and prevents excessively early flowering. By avoiding flower opening and pollen release during periods of unstable weather (such as late spring rainfall and strong winds), the trees enhance pollen transport and successful pollination.