Impacts of climate change on the phenology and distribution range of Castanea sativa (Mill.) varieties in the Cévennes mountainous region, Southern France

Climate change is expected to significantly impact agriculture by altering temperature and precipitation patterns, with notable effects on crop phenology and yields in Mediterranean regions. The European chestnut (Castanea sativa Mill., Fagaceae) is a culturally and economically important species in the Mediterranean area, particularly in mountainous regions of Cévennes in France where traditional chestnut-based agrosystems are under pressure. However, the potential impacts of climate change on chestnut phenology and varietal adaptation remain poorly investigated. This study used the process-based model PHENOFIT to assess the suitability of future climatic conditions (under scenarios RCP4.5 and RCP8.5) for three major chestnut varieties grown in Cévennes mountains. Originally developed for forest trees, this model estimates tree fitness based on survival and reproductive success under specific pedoclimatic conditions. A network of on-farm monitoring sites and a citizen-science approach provided phenological and climatic data to model the consequences of climate extremes and global warming on a shift of the cultivation area until 2100. Model projections suggest an upward and downward elevational expansion of potentially suitable chestnut growing areas, alongside a phenological advance from budburst to fruit maturation. Risks of spring and autumn frosts are projected to decline and winter warming is not projected to compromise exposure to chilling temperatures that break bud dormancy. Chestnut varieties showed different responses to climate change, indicating the need for further studies on their functional traits, especially drought tolerance, varietal plasticity and fruit quality, to enhance the model’s projections’ reliability and propose adaptive strategies for sustainable chestnut cultivation in the upcoming decades.