Plasticity and leaf functional trait divergence in Mediterranean shrubs across contrasting forest successional stages

Shifts in leaf functional traits and their interrelationships are expected to mirror plant ecological strategies throughout successional gradients. However, little is known about how these traits and their correlations vary across ecological scales during succession, particularly in Mediterranean ecosystems. This study examines the variability of leaf functional traits and CSR (Competitor, Stress-tolerant, Ruderal) strategies across and within Phillyrea angustifolia, Pistacia lentiscus, and Quercus coccifera growing in a matorral and a nearby sacred grove, representing contrasting successional stages and environmental conditions. For each species, 10 individuals per site were assessed for two ecophysiological traits (relative chlorophyll content and leaf thickness) and three structural allocation traits (leaf tissue density, specific leaf area, and leaf dry matter content), along with CSR strategies. Trait responses to changes in soil nutrients, light, and water availability during succession were both species- and trait-specific. When considering all species together, trait correlations aligned with those described by the global leaf economic spectrum. Thus, Q. coccifera and P. angustifolia shifted from conservative or stress-tolerant strategies in the matorral, viewed as a regressive successional stage, toward more acquisitive or competitive strategies in the sacred grove, regarded as a climax stage. Structural allocation traits showed high intraspecific variation and inconsistent within-species correlations, making them reliable indicators of local-scale adaptive strategies. In contrast, ecophysiological traits exhibited more stable relationships across scales and were largely driven by interspecific variation, limiting their usefulness for predicting intraspecific responses along local successional gradients.