PARENT SESSION
Contributed Oral Session 16: Photosynthesis and Water Relations: Conductivity; Stress
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 524 A, Level 5, Palais des congrès de Montréal
Does freezing set the latitudinal limit of mangrove forests?
Stuart, Stephanie*,1, Choat, Brendan1, Holbrook, Michele1, Ball, Marilyn2, 1 Harvard University, Canbridge2 Australian National University, Canberra
ABSTRACT- Coastal wetlands are dominated by mangrove forests in the tropics, and by salt marshes at higher latitudes. This world-wide transition from woody to herbaceous vegetation has long been attributed to temperature, but fundamental mechanisms excluding woody plants from tidal habitats at high latitudes are unknown. One possibility is that freeze-thaw events could reduce the capacity for water transport to leaves and stems. Dissolved gases excluded from developing ice crystals may form bubbles that expand on thawing, causing conduits to become embolised, blocking water flow. Mangroves could be particularly vulnerable to this type of freezing injury because their xylem sap is subject to large negative pressures, or tensions, even when transpiration is low, due to soil salinity. Tension is an important determinant of bubble expansion; the more negative the pressure, the greater the probability that a bubble will nucleate an embolism. Here we show that constraints on water transport caused by interactions between xylem tension, conduit diameter, and freezing temperatures impose latitudinal limits on the distribution of halophytic trees.
Key words: Mangrove, Freeze-Induced Embolism, Avicennia, Rhizophora