The relationship between heat units trends and reproductive development in olive (Olea europaea, L.) was studied over a 3-year period (1999-2001) in 15 areas in the southern Italian regions of Campania, Calabria, Puglia, and Sicily. Heat units were calculated using GDH and GDD formulas and the flowering phases in the olive groves were studied using volumetric pollen traps that aspirate fixed quantities of air. With this method, the olive pollen release and flowering trends were determined. The main objective of the study was to correlate the spring heat unit amounts and the phases of maximum pollen emission with the date of flowering. Moreover, the ranges of GDH and GDD in the different study areas were calculated to identify maps of olive pollen release.
Fabio Orlandi, Bruno Romano and Marco Fornaciari
Fabio Orlandi, Carlo Sgromo, Tommaso Bonofiglio, Luigia Ruga, Bruno Romano and Marco Fornaciari
Several bioclimatic studies have been developed over recent years considering temperature trends and their influence on vegetative and reproductive phenomena during plant growth. In the applied aerobiology laboratory of Perugia University, various studies of olive (Olea europaea L.) flowering and its relationship with climatic variables have been conducted. Since 1999, a flowering monitoring network in central–southern Italy has been working to track the biological phenomena over the years, the possible differences between the monitoring stations, and the relationships with climate. Olive flowering was monitored in 15 monitoring stations located in four Italian regions (Campania, Calabria, Puglia, and Sicily) representing ≈90% of national olive territories. The flowering phenophase was studied through pollen emission monitoring, making use of scientific instruments that capture defined volumes of atmosphere and allow us to ascertain the pollen emission trends, thereby determining daily average pollen concentrations (pollen grains/m3). The combined analysis of pollen monitoring and meteorological data permitted identifying various groups of stations characterized by the fact that better relationships between reproductive structure development and growing degree-days are obtained with different spring threshold temperatures (low 7 to 10 °C or high 11 to 14 °C). Moreover, the study permitted demonstrating particular meteorological and biological behaviors, providing useful information about plant–climate relationships in a species of economic interest affected by interincompatibility.