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Physiological Section

Watson, Kimberley A. [1], Pratt, R. Brandon [1], Davis, Stephen D. [1].

Drought Tolerance and Post-fire Regeneration in California Chaparral.

Drought tolerance and regeneration after wildfire affect chaparral shrub distributions in southern California. It was hypothesized that after wildfire, species regenerating exclusively from seed (non-sprouters) would have leaves more resistant to water stress than species that exclusively sprout (obligate sprouters) and species that both resprout and establish seedlings after wildfire (facultative sprouters). We examined the response of leaves to water stress for nine seedling species grown in a common garden. All species were from the family Rhamnaceae with three species from each of three life history types: non-sprouting, obligate sprouting, and facultative sprouting. Leaves were dehydrated to determine their water potentials at the turgor loss point, osmotic potentials at full hydration, rates of water loss, decline in chlorophyll fluorescence, and minimum conductance to water vapor. Results indicated significant differences in water potentials where stomata closed: -4.4 MPa for non-sprouters and -3.4 MPa for obligate and facultative sprouters. For leaves dehydrated in a laboratory, non-sprouters lost leaf turgor at -3.7 MPa whereas obligate and facultative sprouters lost turgor at about -3.2 MPa. We conclude that within the family Rhamnaceae, leaves of non-sprouting species are more drought-tolerant than both obligate and facultative sprouting species and may reflect adaptive exploitation of post-fire canopy gaps not occupied by the fire-persistent root crowns of sprouters.


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1 - Pepperdine University, Natural Sciences Division, 24255 Pacific Coast Highway, Malibu, California, 90263-4321, USA

Keywords:
chaparral
wildfire
drought
stomatal conductance
life history strategy
seedlings
drought tolerance.

Presentation Type: Poster
Session: 33-70
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM
Abstract ID:73


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