PARENT SESSION
Oral Session #55: Fire Ecology. Presiding: M. Moritz.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas H.

Why do non-sprouters exist? Seedling drought tolerance in resprouting and non-sprouting populations of Ceanothus tomentosus.

Schwilk, Dylan¹, Ackerly, David¹, ¹

ABSTRACT- Although the ability to resprout is widely assumed to be the ancestral condition in most plant groups and failure to sprout the derived, many species that depend upon fire-cued seed germination lack the ability to resprout. Most models for the evolution of non-sprouting assume a tradeoff between seedling success and vegetative resprouting ability of adults. Such models require high non-sprouter seedling success rates relative to resprouters. There is reason to believe that competitive differences among chaparral species might result from different seedling growth rate or drought tolerance. To test the hypothesis that non-sprouting plants have higher growth rates and/or drought survival, we grew seedlings of Ceanothus tomentosus from sprouting and non-sprouting populations in a common garden experiment. Each of these C. tomentosus populations was paired with a sympatric Ceanothus species that differed in resprouting ability. Early seedling growth rates were higher among non-sprouting populations. Non-sprouters were more resistant to xylem embolism under low water treatments than were resprouters. This evidence is consistent with the hypothesis that non-sprouting should be associated with increased seedling drought tolerance.

KEY WORDS: fire, resprouting, drought, Ceanothus