Analysis of olive tree flowering behavior based on thermal requirements : a case study from the northern Mediterranean region

Podgornik, Maja (author), Fantinič, Jakob (author), Pogačar, Tjaša (author), Zupanc, Vesna (author)

Abstract In recent years, early olive fruit drop has been observed in the northern Mediterranean regions, causing significant economic losses, although the exact cause remains unknown. Recent studies have identified several possible causes; however, our understanding of how olive trees respond to these environmental stresses remains limited. This study includes an analysis of selected meteorological and flowering data for Olea europaea L. “Istrska belica” to evaluate the use of a chilling and forcing model for a better understanding of flowering time dynamics under a changing climate. The flowering process is influenced by high diurnal temperature ranges (DTRs) during the pre-flowering period, resulting in earlier flowering. Despite annual fluctuations due to various climatic factors, an increase in DTRs has been observed in recent decades, although the mechanisms by which olive trees respond to high DTRs remain unclear. The chilling requirements are still well met in the region (1500 ± 250 chilling units), although their total has declined over the years. According to the Chilling Hours Model, chilling units—referred to as chilling hours—represent the number of hours with temperatures between 0 and 7.2 °C, accumulated throughout the winter season. Growing degree hours (GDHs) are strongly correlated with the onset of flowering. These results suggest that global warming is already affecting the synchrony between olive tree phenology and environmental conditions in the northern Mediterranean and may be one of the reason for the green drop.

• Language: English
• Keywords: Olea europaea L., phenology, chilling hours, diurnal temperature range, climate change
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 19 str.
• Numbering: Vol. 13, iss. 8, art. 156
• PID: 20.500.12556/RUL-171121
• UDC: 634.63
• ISSN on article: 2225-1154
• DOI: 10.3390/cli13080156
• COBISS.SI-ID: 243661571
• Publication date in RUL: 06.08.2025

Record is a part of a journal

• Title: Climate
• Shortened title: Climate
• Publisher: MDPI AG
• ISSN: 2225-1154
• COBISS.SI-ID: 523031833

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: oljka, fenologija, hlajenje, dnevni temperaturni razpon, podnebne spremembe