PARENT SESSION
Oral Session # 40: Fire Ecology II: Forests.
Presiding: D Falk
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.

Landscape fire ecology: Using fire compartment size to predict presettlement fire frequency.

Frost, Cecil^*,1, ¹ North Carolina Plant Conservation Program, Raleigh, North Carolina

ABSTRACT- One of the emergent properties of the new field of Landscape Fire Ecology is the apparent control of fire frequency in some regions by the size of their fire compartments. Other things being equal in a given landscape, the larger the fire compartment the higher the fire frequency. In the presettlement landscape, fire frequency may have been driven in some regions by Native Americans and in others by lightning ignitions. Development of mechanisms of fire dependence might be expected to take evolutionary time. Immigration of man into the Western Hemisphere occurred only 12-20,000 years ago. Since that length of time would provide too few generations for us to expect evolution of complex adaptations to fire, we might expect that truly fire dependent species would be concentrated in those areas where lightning dominated the fire regime. The national pattern of lightning strikes illustrates hot spots for lightning activity in such places as central Arizona and the Southeastern Coastal Plain. In the Southeast there appear to be hundreds of fire dependent species. In 20 years of monitoring one of these, Venus flytrap has been shown to require a mean fire frequency of 1-3 years for survival, making it the most frequent-fire dependent species yet documented. Further, the distribution of Venus flytrap provides substantiation of the relationship of fire compartment size to presettlement fire frequency. In the West, the relationship of fire compartment size to fire frequency may have been obscured by the very large size of fire compartments, but a rare wetland plant, Huachuca water-umbel (Lilaeopsis schaffneriana,/i> ssp. ,i>recurva) appears to be a frequent fire analog of Venus flytrap. The pattern of such fire-frequency indicator species in landscape fire compartments tells us enough about the original fire frequency that they can be used as one line of evidence for mapping presettlement fire regimes.

Key words: Rare Species, Fire Ecology, Dionaea muscipula