title: Comparative community physiology: nonconvergence in water relations among three semi-arid shrub communities.
abstract: Plant adaptations to the environment are limited, and therefore plants in similar environments may display similar functional and physiological traits, a pattern termed functional convergence. Evidence was examined for functional convergence among 28 evergreen woody shrubs from three plant communities of the semi-arid winter rainfall region of southern California. Both leaf and water relations traits were examined, including seasonal stomatal conductance (gs), specific leaf area (SLA), leaf specific conductivity (Kl), seasonal water potential (Psi w), stem cavitation resistance (Psi 50), and xylem density. Species display community-specific suites of xylem and leaf traits consistent with different patterns of water use among communities, with coastal sage scrub species utilizing shallow pulses of water, Mojave Desert scrub species relying on deeper water reserves, and chaparral species utilizing both shallow and deep moisture reserves. Communities displayed similar degrees of water stress, with a community-level minimum Psi w (Psi wmin) of c. -4.6 Mpa, similar to other arid communities. Pooled across sites, there was a strong correlation between Psi wmin and xylem density, suggesting that these traits are broadly related and predictive of one another. This comparative community physiology approach may be useful in testing hypotheses of functional convergence across structurally similar semi-arid communities.
authors.affiliation: Department of Biology, California State University, Bakersfield, 14 SCI, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Jacobsen
authors.affiliation: Department of Biology, California State University, Bakersfield, 14 SCI, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA.
authors.forename: R Brandon
authors.initials: RB
authors.lastname: Pratt
authors.affiliation: Natural Science Division, Pepperdine University, 24255 Pacific Coast Hwy, Malibu, CA 90263, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Davis
authors.affiliation: Biological Sciences Department, California State Polytechnic University, 3801 West Temple Ave, Pomona, CA 91768, USA.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Ewers
mesh_terms: D000222:Adaptation, Physiological; D044822:Biodiversity; D001696:Biomechanical Phenomena; D002140:California; D004777:Environment; D063245:Plant Development; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D018521:Plant Physiological Phenomena; D054046:Plant Stomata / Q000502:physiology; D010944:Plants / Q000033:anatomy & histology / Q000378:metabolism*; D011891:Rain; D012621:Seasons; D013045:Species Specificity; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000033:anatomy & histology / Q000502:physiology
chemical_list: D014867:Water