PARENT SESSION
Oral Session # 6: Fire Ecology I: Structure and Demographics
Presiding: R Parmenter
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.

Demographic variation with fire in an endemic mint.

Quintana-Ascencio, Pedro^*,1, Menges, Eric¹, Weekley, Carl¹, Gaoue, Orou¹, ¹ Archbold Biological Station, Venus, Florida, USA

ABSTRACT- We report analyses of the demography of the narrowly endemic, endangered Florida scrub mint Dicerandra frutescens based on data collected from 1988-2000. Data include survival, growth, and estimated fecundity of thousands of plants in 7 populations, as well as 10 seed bank/germination experiments. Demographic patterns are driven by fire. Finite rates of increase (lambda) calculated from 79 stage-structured transition matrices are highest shortly after fire and decline (fit with an inverse function) sharply through 10 years postfire. The break-even value of =1 is passed quickly, in about 6 years postfire, suggesting that older populations are already facing decline. Population decline is probably related to rapid shrub growth in the habitat of D. frutescens . In long-unburned sites, finite rates of increase were negative ( < 1) but they were no lower than rates found in sites 9-10 years postfire, suggesting some degree of persistence of D. frutescens in long-unburned sites. Firelanes, road edges, and other disturbed areas also provide habitats for D. frutescens . In abandoned firelanes and an irrigated suburban site, finite rates of increase were often > one. However, such sites may not offer stable environments for species persistence.

Key words: Lake Wales Ridge, rare, demography, matrix modeling