Floristic Composition and Species Richness of Subtropical Seasonally Wet Muhlenbergia sericea Prairies in Portions of Central and South Florida Steve L. Orzell Avon Park Air Force Range, 29 South Blvd., Avon Park Air Force Range, FL 33825-5700
[email protected] Edwin Bridges Botanical and Ecological Consultant, 7752 Holly Tree Place, NW, Bremerton, WA 98312-1063
[email protected] ABSTRACT Fire-maintained, species-rich, seasonally wet subtropical grasslands dominated by muhly grass (Mu- hlenbergia sericea ), here referred to as calcareous wet prairies, occur on mineral soils between pine- lands (or Florida dry prairies) and herbaceous wetlands. Southern Florida calcareous prairies/pinelands are described based upon species composition, species richness, niche or habitat breadth, taxonomic uniqueness, and geographic area. This study differentiated three calcareous prairie/pineland regions, central, south-central, and south Florida. A south-central Florida community type occurs sporadically from Polk County south to Okeechobee, Hendry, and Sarasota counties, in an otherwise acidic prairie/ pineland landscape. Quantitative sampling using nested and non-nested modules in Polk and Okeechobee counties was utilized to determine fine-scale species richness values. Results indicate that these prairies have among the highest fine-scale vascular plant species richness values recorded in North America, up to 27 species in 0.1 m2, 49 species in 1 m2, and 171 species in 1000 m2. Floristic lists compiled from 43 sites in 14 southern Florida counties demonstrate that many sites have biodiversity significance with over 100 species. Several have 140-180 species recorded from single-event visits. The community species pool consists of 412 taxa from south-central Florida calcareous prairies alone with 548 taxa when south Florida calcareous pineland/prairies are included.