Document: JEA-3-32-8

Hydraulic properties and freeze-thaw induced embolism in 17 sympatric species of oaks (Quercus.)

CAVENDER-BARES, J.* and N.M.HOLBROOK

Harvard University, Cambridge, MA 02138 USA ¹

Abstract:
We investigated hydraulic properties of seventeen species of oaks (Quercus) that occur sympatrically in northern central Florida. Leaf bearing stems from species in the section Lobatae (red/black oaks) had significantly higher specific conductivity and greater mean vessel diameters than species in the section Quercus s.s. (white oaks), while species of the subsection Virentes (live oaks) had intermediate values. Evergreen species had significantly higher Huber values (ratio of sapwood area to distal leaf area) than deciduous species, however, there were no consistent differences in conductivity or vessel diameters between evergreen and deciduous species. Across all species, specific conductivity was significantly correlated with mean vessel diameter and with the hydraulic contribution of vessels (r⁴). There were substantial differences in specific conductivity between species, while average vessel diameters showed less interspecific variation. There were also large differences between species and between clades in freeze-thaw induced embolism. Deciduous species, on average, showed greater vulnerability to freezing than evergreen species. However, this effect may be largely due to the significantly higher vulnerability of white oaks, which are all deciduous, compared to live and red/black oaks, which include evergreen species. These results highlight the importance of taking evolutionary lineage into account in comparative physiological studies.

Keywords: hydraulic architecture, freeze-thaw, embolism, Quercus, evolutionary lineage

This abstract is being presented at: 3:15 PM in session:
Oral Session #34: Water Relations in Trees.