Temperature trends of the olive tree cultivation period in the producing areas of Spain (1981-2019)

Olive tree is mainly cultivated in the temperate zones of the Mediterranean area. Temperatures are the main factors to evaluate the climatic suitability for olive cultivation. A study of the spatial and temporal variations of temperatures in a territory is necessary to define the most appropriate areas for production, as well as to evaluate different varieties. Spain has the largest area and high production of olives in the world. In this study, the trends of the average temperature of the olive growing period are analyzed by defining the olive growing station temperature (OGST) index. The active days for the olive tree were defined as those in which the average daily temperatures are above 14.4°C between April and October. The minimum and maximum daily temperatures of 12 meteorological stations, from the meteorological services of the Spanish government (AEMET), located in the main olive growing areas (more than 90% of the olive production in Spain is found in these areas) were used, considering a period from 1981 to 2019. Mann-Kendal test and Sen’s slope were applied to determine the trends and their magnitude. Results showed that all days between June and September were active days. The mean OGST value was 21.5°C, varying between 20.1°C in Albacete and 23.6°C in Seville. It was also shown a significant increasing trend in the index in all areas. Temperatures in the olive tree growth period had increased by an average of 0.5°C per decade, which represents an average increase of 1.9°C between 1981 and 2019.