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Biology of Dryland Plants

Pratt, R. Brandon [1], Jacobsen, Anna L. [2], Ewers, Frank W. [2], Davis, Stephen D. [1].

Drought tolerance and life history in Rhamnaceae shrub species.

Chaparral shrub species survive wildfire by three different life histories: non-sprouters (NS) are killed by fire, thus populations reestablish only through germination of fire-stimulated seeds; facultative sprouters (FS) reestablish by both vegetative sprouting and seed germination; and obligate sprouters (OS) reestablish only by vegetative sprouting because seeds are killed by fire. Previous data suggest that post-fire seedlings of NS and FS reestablish as open canopy, gap specialists. In contrast, seedlings of OS primarily reestablish in deep shade during fire-free intervals. We hypothesized that these differences in life history and seedling microsite preference, compared within the Rhamnaceae, would result in differential resistance to water stress such that NS>FS>OS. Among adults growing in the field, the general pattern for xylem cavitation resistance of stems and roots was NS>FS=OS. Among potted seedlings grown in a common garden the pattern was similar. Among these same potted seedlings during summer drought, NS exhibited 10% mortality, FS 50%, and OS about 40% mortality, while mortality of irrigated controls remained low across all life histories. Consistent with our hypothesis, NS were the most resistant to water stress at the adult and seedling stage of development. Water stress resistance was not different between FS and OS species. Life history is linked to resistance to water stress especially for the NS strategy that relies on seeding recruitment for persistence and reestablishment in open canopy gaps.

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1 - Pepperdine University, Natural Sciences Division, 24255 Pacific Coast Highway, Malibu, California, 90263-4321, USA
2 - Michigan State University, Department of Plant Biology, 166 Plant Biology, East Lansing, Michigan, 48824, USA

none specified

Presentation Type: Symposium or Colloquium Presentation
Session: 49-12
Location: Salon K - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 1:45 PM
Abstract ID:88

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