Vein and stomatal traits in leaves of three co-occurring Quercus species differing in leaf life span

We analyzed vein and stomatal traits (vein density and vein volume per leaf area, stomatal density, stomatal pore length and pore index) and their relationships with other morphological traits [leaf area, leaf thickness and leaf mass per unit area (LMA)] of three co-occurring Mediterranean tree species with contrasting leaf habits [Quercus faginea Lam., Q. suber L. and Q. ilex L. subsp. ballota (Desf.) Samp.]. The results showed that leaf size, thickness and LMA varied among the species in parallel with the differences in leaf longevity. By contrast, the traits most related to water use showed inconsistent differences among the three species. Stomatal pore index was lowest in the species with intermediate leaf life span. The species with longest leaf longevity had highest vein density but minimum vein volume per area. Vein and stomatal traits also varied independently from other leaf traits within each species. The absence of association between LMA and vein volume suggests that a large LMA is the result of the accumulation of other tissues, and not necessarily veins. We concluded that in contrast with most economic leaf traits that tend to vary in parallel with leaf life span, traits related to water use varied inconsistently with leaf duration in the three species studied. Stomatal and vein traits, in addition, were not related to the maximum stomatal conductance of the different species.