Biology of Dryland Plants
Preston, Katherine , Bhaskar, Radika .
Resprouts revisited: functional changes three years after afire.
Evergreen shrubs in the southern California chaparral experience soil water deficits every summer and are also subject to periodic fires that burn their canopies completely. After a fire, many chaparral shrub species regenerate their lost canopies by initiating new shoots from their living root mass. In an earlier study, we found that the high root-to-leaf area ratio of newly resprouting plants dramatically improved water status in shoots of six co-occuring shrub species. Water potentials were less negative than comparable full-canopy individuals, transpiration rates were much higher, and specific leaf areas were greater. We also found that resprouting plants had lighter wood than conspecific full-canopy individuals. We revisited our study site near Santa Barbara, CA, three years after the fire as resprouting plants were returning to their full-canopy state. We predicted that many of the shoots initiated immediately after the fire would have died, either through competition among shoots or because of total hydraulic failure due to drought or freeze-induced cavitation. Surprisingly, we found no evidence of failed shoots or thinning canopies. Individuals of most species maintained a crowded and vigorous cohort of regrowing shoots. However, there has been a shift in leaf structure since the fire for most species; specific areas of recently matured resprout leaves did not differ from SLAs in conspecific full-canopy individuals, and were much lower than SLAs of leaves measured when shoots were newly initiated. We also found variation in the density of wood made each year after the fire. Wood density has generally increased over three years, although developmental patterns overlay this trend. As leaf area increases relative to root mass in these species, several functional traits are returning to pre-fire values.
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1 - Stanford University, Biological Sciences, 371 Serra Mall, Stanford, California, 94305, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Salon K - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 1:30 PM