Global warming impact on floral phenology of fruit trees species in Mediterranean region

• Global warming was observed in the Mediterranean region.
• High sensitivity of flowering advance was remarkable in late-spring-flowering species.
• Flowering earliness was related to mean temperature during forcing period.
• Physiological processes of trees explain the difference observed in flowering dates.
• Phenology of trees in the northern areas was expected to stand some vulnerability.

This study was carried out in three geographically contrasting countries of the Mediterranean region. It aims to understand the impact of climate change, particularly the temperature increases, on phenological stage of three taxonomically different species (early and late-spring-flowering species). Three species, namely olive (Olea europaea), apple (Malus domestica Borkh.) and almond (Prunus dulcis (Mill.)) were investigated to highlight the phenological behavior of one species at different locations and different species at one location. Climatic and phenological data were collected from Morocco, France and Italy over the last 40 years. Analysis of data on temperature showed a strong warming in the northern locations (coldest areas), particularly in Nîmes, compared to the southern ones (warmer locations) during the period October to May. The marked spring warming in all locations since the end of 1980s in France (the beginning of 1990s in Italy and Morocco) resulted in blooming earliness, with regional patterns in terms of impact. The late-spring-flowering species (olive and apple) showed a remarkable sensitivity to continuous warming in different areas. No flowering earliness was observed in early-spring-flowering species (almond), due to the stability of mean temperature during February. Thus, a strong control of mean temperature during the forcing period on flowering earliness of apple was found in all areas. Physiological processes (dormancy and dormancy release) of trees during the dormant and growth period explain, in part, the regional differences observed in flowering dates among sites and species. Overall, the pronounced warming in the southern France reflects a relative trend toward aridity of climate at this site, and consequently some vulnerability of fruit trees. As result, the process of flowering in a high latitude locations (northern areas) in the future can be represented by that in a low latitude locations at present (southern areas), particularly for apple.