Crandall, Raelene , Platt, William .
Persistence of woody reseeders and resprouters (Hypericum spp.) along fire-frequented ecoclines of the northern Florida gulf coast.
Woody shrubs can be divided into reseeding and resprouting life histories based on responses to disturbances. After fire, reseeders germinate from dormant seeds; resprouters regrow from underground structures. Reseeders and resprouters are predicted to be restricted to habitats with long and short disturbance return intervals, respectively. Nonetheless, resprouters and reseeders of shrubs co-occur along Gulf of Mexico coastal ecoclines that experience frequent lightning fires (> twice a decade). In these ecosystems, fires ignited in upland communities move into mesic lowland areas in years when fuels and climatic conditions are favorable. We hypothesize that resprouters and reseeders coexist in frequently burned habitats because fires along coastal ecoclines are heterogeneous in time and space. Thus, reseeders should be associated with uplands where fires tend to burn frequently and evenly across the landscape. In contrast, reseeders should be associated with lowlands; fires spreading from uplands should burn increasingly patchily in progressively wetter areas. We used five belt transects of 50 1m2 plots positioned along coastal ecoclines to examine habitat associations of Hypericum microsepalum (resprouter), H. brachyphyllum (facultative reseeder/resprouter), and H. chapmanii (obligate reseeder). Data indicate these species are separated along a gradient in topography and soil moisture. Hypericum chapmanii and H. microsepalum are separated spatially, with the former in low drainages and the latter in upland flatwoods. Hypericum brachyphyllum is intermediate in distribution and occasionally co-occurs with H. chapmanii. Because recent fires were frequent in dry, upland habitats, and less common in adjacent mesic, lowland habitats, we propose that a fire-flooding interaction controls the distribution of reseeders and resprouters. The patchy nature of lightning fires could, thereby, enhance persistence of reseeders and resprouters in areas with historically frequent fires, despite needing different frequencies for persistence.
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1 - Louisiana State University, Biological Sciences, Baton Rouge, LA, 70803, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 4:45 PM