Community Level Comparisons Of Leaf Traits And Water Relations Of Woody Plants In Three Southern California Habitats: Coastal Sage Scrub, Oak Woodland, And Riparian Woodland

California is a biodiversity hotspot with Mediterranean climate characterized by cool, wet winters and hot, dry summers.  Coastal southern California contains a mosaic of plant communities that are often physically close, but visually distinct.  To test the prediction that community averages of leaf traits are related to insolation (solar radiation) and water availability, we compared leaf traits and plant water relations in adjacent Coastal Sage Scrub (9 species), Oak Woodland (7 species), and Riparian Woodland (11 species) habitats.  We hypothesized that vegetation in habitats with greater soil temperature, insolation, and lower soil moisture would have smaller, thicker leaves, lower stomatal conductance, and lower stem water potentials.  Soil temperature, insolation, and soil moisture were measured during two days in June 2011 to determine differences in abiotic factors across the sites.  Leaf size, specific leaf area, stomatal conductance, and stem water potential in plants from the three habitats were measured.  These traits were analyzed both weighted and unweighted for species abundance in each habitat.  Leaf morphology differed significantly among the plant communities from the three habitats.  Leaf size and specific leaf area were greater in environments with lower soil temperature, insolation, and greater soil moisture.  On the day of measurements, we found no significant differences in stomatal conductance and stem water potential among the three habitats.  This study confirmed previous findings for chaparral vegetation in northern California that leaf traits are closely related to insolation and water availability and extended those findings into more mesic oak and riparian woodland habitats.