THE INFLUENCE OF FIRE ON SPARTINA-PECTINATA WETLAND COMMUNITIES IN A NORTHEASTERN KANSAS TALLGRASS PRAIRIE

Wetlands dominated by the C-4 grass Spartina pectinata were investigat ed to quantify differences in plant species composition and diversity in response to fire frequency. The study site was a tallgrass prairie in northeastern Kansas that included Spartina wetlands subjected to sp ring fires at 1-, 2-, 4-, 10-, and 20-year intervals. Because C-3 forb s in these wetlands responded strongly to different fire frequencies, the light environment and gas exchange responses of the ubiquitous for b Asclepias syriaca were also assessed. In general, species diversity was lower in annually burned wetlands because of lower forb diversity. Maximum H' in annually burned sites was 1.64 versus 2.77 in 10- and 2 0-year burned sites. However, individual forb responses varied. Asclep ias increased and Solidago canadensis and Galium aparine decreased in importance with increasing fire frequency. Canopy sunlight interceptio n was greater in annually burned wetlands than in wetlands with lower burn frequencies. Despite reduced light availability, midseason photos ynthetic rates of Asclepias were higher in annually burned sites. The results suggest that frequent fire in tallgrass prairie wetlands resul ts in less diverse plant communities, similar to responses of upland p rairie, and that the timing of fire, relative to life history and phen ology of the subordinate species, strongly influences responses of ind ividual forbs.