Biometeorol

Int J Biometeorol (2005) 49:184–188 DOI 10.1007/s00484-004-0223-5

ORIGINAL ARTICLE

C. Galµn · H. García-Mozo · L. Vµzquez · L. Ruiz · C. Díaz de la Guardia · M. M. Trigo

Heat requirement for the onset of the Olea europaea L. pollen season in several sites in Andalusia and the effect of the expected future climate change
Received: 1 October 2003 / Revised: 13 May 2004 / Accepted: 24 June2004 / Published online: 27 July 2004  ISB 2004

Abstract Olives are one of the largest crops in the Mediterranean region, especially in Andalusia, in southern Spain. A thermal model has been developed for forecasting the start of the olive tree pollen season at five localities in Andalusia: Cordoba, Priego, Jaen, Granada and Malaga using airborne pollen and meteorological data from 1982 to2001. Threshold temperatures varied between 5C and 12.5C depending on bio-geographical characteristics. The external validity of the results was tested using the data for the year 2002 as an independent variable and it confirmed the model’s accuracy with only a few days difference from predicted values. All the localities had increasingly earlier start dates during the study period. This couldconfirm that olive flower phenology can be considered as a sensitive indicator of the effects of climate fluctuations in the Mediterranean area. The theoretical impact of the predicted climatic warming on the olive’s flowering phenology at the end of the century is also proposed by applying Regional Climate Model data. A general advance, from 1 to 3 weeks could
C. Galµn ()) · H. García-Mozo · L.Vµzquez Departamento de Biología Vegetal, Universidad de Córdoba, Colonia San JosØ no. 4, Campus Universitario Rabanales, 14071 Córdoba, Spain e-mail: bv1gasoc@uco.es Tel.: +34-957-218719 Fax: +34-957-218598 L. Ruiz Departamento de Biología Vegetal, Universidad de JaØn, JaØn, Spain C. D. de la Guardia Departamento de Biología Vegetal, Universidad de Granada, Granada, Spain M. M. Trigo Departamento deBiología Vegetal, Universidad de Mµlaga, Mµlaga, Spain

be expected, although this advance will be more pronounced in mid-altitude inland areas. Keywords Olea europaea · Pollen · Aerobiology · Threshold temperature · Climate change

Introduction
Olive (Olea europaea) growing is one of the major economic activities in the Mediterranean region, especially in the south. Spain produces 33% of theworld’s total olive oil and the region of Andalusia accounts for 80% of total Spanish production. In this region, olive-growing is concentrated in central and eastern areas. Olive flower phenology is characterized by bud formation during summer, dormancy during autumn, budburst in late winter (February) and flowering in late spring (May–June). For late-spring-flowering trees, thermal models basedsolely on thermal accumulation are the most suitable for predicting the start of the pollen season (Chuine et al. 1998, 1999). The Mediterranean region is characterized by a changeable climate, especially in spring when temperature varies quickly from one day to another. Moreover, inter-annual variations affect pollen production and the timing of flowering. Thermal models use a thresholdtemperature. The threshold temperature can vary according to several factors in both the plant and the environment (Snyder et al. 1999; Chuine and Cour 1999; Wielgolasky 1999). Thermal models suggest that olive phenology may be a sensitive indicator of interannual trends in spring temperature, and have potential to be used as a measure of the biological impact of future climatic warming (Osborne et al.2000). Several papers have addressed the bio-climatic requirements before the start of the O. europaea pollen season in different sites in Andalusia, but these studies were performed using a different methodology for each location (Alba and de la Guardia 1998; Galµn et al. 2001; Gonzµlez-Minero and Candau 1996). The aim of this paper was to compare the start of the O. europaea pollen

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