Phenological models to predict the main flowering phases of olive (Olea europaea L.) along a latitudinal and longitudinal gradient across the Mediterranean region.

The aim of the present study was to develop pheno-meteorological models to explain and forecast the main olive flowering phenological phases within the Mediterranean basin, across a latitudinal and longitudinal gradient that includes Tunisia, Spain, and Italy. To analyze the aerobiological sampling points, study periods from 13 years (1999-2011) to 19 years (1993-2011) were used. The forecasting models were constructed using partial least-squares regression, considering both the flowering start and full-flowering dates as dependent variables. The percentages of variance explained by the full-flowering models (mean 84 %) were greater than those explained by the flowering start models (mean 77 %). Moreover, given the time lag from the North African areas to the central Mediterranean areas in the main olive flowering dates, the regional full-flowering predictive models are proposed as the most useful to improve the knowledge of the influence of climate on the olive tree floral phenology. The meteorological parameters related to the previous autumn and both the winter and the spring seasons, and above all the temperatures, regulate the reproductive phenology of olive trees in the Mediterranean area. The mean anticipation of flowering start and full flowering for the future period from 2081 to 2100 was estimated at 10 and 12 days, respectively. One question can be raised: Will the olive trees located in the warmest areas be northward displaced or will they be able to adapt their physiology in response to the higher temperatures? The present study can be considered as an approach to design more detailed future bioclimate research.

Climate change impact on the olive pollen season in Mediterranean areas of Italy: air quality in late spring from an allergenic point of view.

Recent studies have shown that there are many effects of climate change on aeroallergens, and thus on allergic diseases in humans. In the Mediterranean region, despite the importance of the olive tree for production, there is high allergenicity of olive pollen and related risks to human health. Aerobiological sampling techniques can be used to analyse the pollinosis phenomenon through determination of mean daily pollen concentrations per cubic metre of air. The present study was carried out from 1999 to 2008 in 16 olive-growing areas in Italy, to update the information on the pollinosis characteristics of Olea europaea in the study areas. The analysis of the average flowering season over the study period highlights a temporal scaling of pollen in the atmosphere that depends on the different climatic characteristics. This is mainly dependent on temperature, and in part, determined by latitude. Generally, the levels of O. europaea pollen in the atmosphere are higher from mid-April to the end of June, with the period of greatest risk to human health due to this olive pollen in this area currently limited primarily to the last 10 days of May. However, the pollen season can move, depending on the climate scenario considered, and data here can be used to determine potential time shifts in pollinosis that might cause more precocious asthma and allergy problems. The allergy season for this type of pollen might be significantly precocious in future decades (20-30 days earlier in the year), which will impact on the severity and duration of allergies attributable to olive tree pollen.

Bioclimatic requirements for olive flowering in two Mediterranean regions located at the same latitude (Andalucia, Spain and Sicily, Italy).

The Mediterranean Region is the major area devoted to olive tree crop, and therefore a study of olive flowering is of great interest for the European Community. On the other hand, olive pollen is one of the main causes of pollen allergy in the Mediterranean area. Olive flowering is affected by climatic factors such as temperature and photoperiod, which vary geographically in latitude and altitude. Temperature has been used to study those processes that lead to flowering in the olive tree. The aim of the present paper is firstly the comparison of the flowering full bloom dates in two Mediterranean areas, Sicily (Italy) and Cordoba (Spain), located in the same latitudinal band (37-38 degrees N) and to calculate the heat requirement until flowering by determination of different threshold temperatures and methods of heat accumulation. A delay of the full flowering dates in the Spanish compared with the Italian olive groves was observed. The most suitable threshold temperatures were carried out in a 7 degrees -15 degrees C range by considering the heat accumulation start on 1 January in each olive grove. In particular, some causes were indicated as responsible for the different threshold temperatures recorded in the 2 study areas: First, the different climatic conditions (continental and insular climate) secondly the different cultivars present in the olive groves.