Il rilascio del polline come indicatore dei cambiamenti climatici: la fioritura dell’olivo nel centro Italia.

In this study we analyzed the correlation between the flowering dates of Olea europaea L. and the mean air temperature in the period from 1982-2001 in an olive growing area of Central Italy (Umbria). The phenological data on flowering phase were registered indirectly through an aerobiological monitoring technique by use of volumetric samplers (VPPS 2000 Lanzoni). For meteorological data (mean temperature) we used both the measurements obtained at the meteorological station located near the pollen release site and the results of the ECMWF general circulation model. The aim of the study was to determine relationships between phenological behaviour of the olive (flowering) and the air temperature trend in the Umbria region. The possibility to utilize the analysis of the ECMWF general circulation model to investigate this correlation was evaluated. The analysis showed that the air temperature greatly influenced the olive flowering date. The variation of the daily mean temperature of ±1 °C in the period before flowering makes the start date of flowering (SF) change by at least ±4.3 days, and the date of maximum flowering (MF) by ±7.2 days. In particular, the advancement of flowering was due to the increase of mean temperature in February, May and June. The results of standardized anomaly of the mean monthly temperature showed a positive anomaly trend during the period 1982-2001 for these three months (February: slope = 0.07 and p(>r)=0.07; May: slope =0.07 and p(>r) = 0.09; June: slope =0.09 e p(>r) = 0.013). Moreover, the results demonstrated that the general circulation model, despite its low horizontal resolution which does not permit us to estimate the micro-climatic variations, can be utilized for these applications.