Functional response and resistance to drought in seedlings of six shrub species with contrasting leaf traits from the Mediterranean Basin and California.

This article investigates the functional responses and drought resistance of seedlings from two post-fire seeder genera—Cistus (semi-deciduous malacophyllous shrubs from the Mediterranean Basin) and Ceanothus (evergreen sclerophyllous shrubs from California)—under extreme drought conditions in a common garden experiment. Despite contrasting leaf traits and differing physiological responses to water stress, including variations in leaf area, osmotic potentials, gas exchange, and fluorescence, the study found no significant difference in overall drought resistance between the genera during the seedling stage. Notably, the two most functionally contrasting species, Cistus ladanifer and Ceanothus pauciflorus, exhibited similar high drought resistance but employed different strategies: C. ladanifer tolerated very negative water potentials with partial leaf shedding, while C. pauciflorus adopted a conservative water-use strategy maintaining evergreen leaves. The findings highlight that generalizations based on genus or functional type may oversimplify complex drought responses, emphasizing the need for detailed ecophysiological studies of Mediterranean-type species, particularly during vulnerable early life stages, to better predict their resilience to climate change-induced fire and drought regimes.