Analysis of the optimal temperatures for the synthesis of carbohydrates during the productive period of the olive tree in the olive-growing areas of Extremadura, Spain.

Climate is considered one of the most influential factors in vegetative development, formation and quality of fruits. The study based on bioclimatic indices and the orography of a territory makes it possible to evaluate its suitability for a specific crop and find areas with particularities. This study shows the analysis and trend of the Number of Days with Optimal Temperatures for Carbohydrate Synthesis (NDCHS), in the 12 olive-growing areas (270,000 ha) of Extremadura (Southwest of Spain). Based on the average daily temperature of the 75 climatic stations located in the olive-growing areas, the NDCHS was calculated for the period 1990-2021. To determine the trend, the Mann-Kendal test and Sen's slope estimator were used, and the Pearson test was used to obtain the correlation between the climatic variables. The results show an annual average of 111 days for the NDCHS. The minimum value was found in Ibores with 100 days and the maximum in Vegas del Guadiana with 120 days. The Pearson correlation obtained a maximum value of 0.848 with the average temperature. The Mann-Kendall test showed significant increasing trends in 8 of the 12 olive-growing areas with a minimum of 0.34 (Sen's slope) in Logrosán-Guadalupe and a maximum of 0.76 for the regions of Alburquerque and Vegas del Guadiana. A general average increase of 0.54 NDCHS per year was found for the olive-growing regions in the period studied.