PARENT SESSION
Oral Session #54: Fire Ecology -- Trees, forests, woodlands.
Presiding: E. Menges
Wednesday, August 7. 8:00 AM to 11:30 AM. Apache Meeting Room, TCC.

Effects of fire on the demography of a savanna oak tree, Quercus engelmannii.

Principe, Zachary^*,1,2, Deutschman, Douglas², Zedler, Paul³, ¹ The Nature Conservancy, Murrieta, CA² San Diego State University, San Diego, CA³ University of Wisconsin-Madison, Madison, WI

ABSTRACT- Engelmann oaks (Quercus engelmannii) generally occur in woodlands scattered throughout a matrix of grassland or low-density shrublands. These open woodlands are prone to fire. Frequent fires and the variability of natural resources limit the recruitment of juvenile oaks. In this study, Englemann oak savannas were monitored for three seasons following prescribed burning to assess the importance of fire to recruitment, growth and survival of juvenile Englemann oaks. Seedling establishment was spatially and temporally variable. Seedling recruitment was observed only in 1998 following the abundant rainfall associated with El Nino. Although seedlings comprised the majority of juvenile oaks, they were present under only a small number of adult trees. Fire behavior was extremely variable within the oak woodlands. Fire damage sustained by juvenile oaks was primarily a function of size. Large oaks received less damage than small oaks. Survival immediately after the fires was a complex function of fire damage, size, burn unit, and location with respect to the canopy of the nearest adult oak. Resprouting following fires was dependent both on the size and damage received by juvenile oaks. Subsequent survival was solely a function of pre-fire size suggesting no delayed effect of fire damage. In additional experiments, we documented high levels of variability in natural fuel load, fuel moisture, seedling recruitment from acorns, and seedling size. These studies provide valuable data for the management of oak savannas. Fire reduces the survivorship of juvenile oaks, with seedlings being especially sensitive. Thus, the impact of fire will depend critically on the density and size distribution of juvenile oaks. Areas with abundant saplings will be resistant to fire-induced mortality, but areas with smaller seedlings will experience dramatic reductions.

KEY WORDS: Quercus , fire, savanna