Olive tree flowering timing response to climate

In the Mediterranean basin, olive trees (Olea europea L.) are one of the most widespread tree crop species. These are adapted to the mild climate, as olive fruit and oil are among the oldest and most important products in this area. Flowering is a critical biological phase that can be highly influenced by weather conditions. The present study was aimed at the development of pheno-meteorological models to explain and forecast the full-flowering dates of olive trees located in the Mediterranean basin. Two olive-growing areas have been considered: Jaen, located in the southeast of Spain, and Perugia, located in central Italy. The forecasting models were constructed using partial least-squares regression. In general, the present dates of full flowering were accurately predicted by the models, and the full cross-validation provided acceptable data. The percentages of variance explained by the full-flowering models were 81% for the Spanish model and 83% for the Italian model. The olive-flowering period is mainly affected by temperature. The maximum temperature in March and April showed a strong negative influence on the fullflowering dates across all of the study area. In addition, the precipitation accumulated during early spring (March) showed a high positive influence on the full-flowering dates. The anticipation of full flowering for the future period from 2081 to 2100 was estimated at 10-11 days.