Coordination of hydraulic and functional traits in ten species of trees of the Sonoran Desert

Leave's vein xylem and stomata hydraulic traits should be critically linked to modulating plant responses to drought in leaves of desert species, influencing traits at the whole-plant level and promoting adaptation. We tested for coordination among leaf vein xylem anatomical traits across different hierarchical orders (hydraulic vessel diameter, vein area, free veins per area, areolas per area, total free veins number, total areola number) and stomatal traits (stomatal size, stomatal density, stomatal index, leaf total stomatal area, leaf total stomatal number) as well as their relationship with the leaf area in ten tree species from the Sonoran Desert scrub, Mexico. Moreover, these traits were correlated with other hydraulic and functional traits associated with resource use strategies (hydroscape area, stem-specific density, leaf mass per area, and leaf phenology). Leaf total stomatal area and number were positively associated with vessel diameters at the midrib and with leaf total free terminal veins and areola number, indicating coordination between water transpiration and transport. Also, interspecific differences fit species along a physiological resource use spectrum, following an exploitative vs. conservative physiological axis. Accordingly, species with lower leaf longevity (LL) and foliage duration at the canopy (FD) displayed higher values of stomatal indices and free vein densities, higher stomata density; and anatomical traits related to higher hydraulic conductance and gas exchange in comparison to species with higher LL and FD. Therefore, in this community, species have been selected to take advantage of different temporal hydrological niches to enhance survival under unpredictable and highly seasonal water availability.