Floristic Composition of the South-Central Florida Dry Prairie Landscape Steve L. Orzell Avon Park Air Force Range, 29 South Blvd., Avon Park Air Force Range, FL 33825-5700 [email protected] Edwin L. Bridges Botanical and Ecological Consultant, 7752 Holly Tree Place NW, Bremerton, WA 98312-1063 [email protected] ABSTRACT Floristic composition of the Florida dry prairie landscape was compiled from 291 sites in nine south-central peninsular counties. Floristic lists were based upon field inventory and compilation from reliable sources to- taling 11,250 site and community type-specific observations and were analyzed by region (Kissimmee River, Desoto/Glades “Big Prairie,” and Myakka). The known vascular flora consists of 658 vascular plant taxa, rep- resenting 317 genera and 115 families. Families with the highest number of species are Poaceae (103), Asteraceae (78), Cyperaceae (76), Fabaceae (23), Scrophulariaceae (20), and Orchidaceae (18). The most diverse genera are Rhynchospora (29), Dichanthelium (17), Ludwigia (13), Xyris (12), and Andropogon (11). Of this flora 24 taxa are endemic to central or southern peninsular Florida, primarily within the pine savanna- flatwood/dry prairie landscape, and 41 taxa are of Floridian biotic affinity. Although most species are not re- gionally specific, a few (Carphephorus carnosus, Ctenium aromaticum, and Liatris spicata) appear to be ab- sent from the Myakka prairie region, while Marshallia tenuifolia appears to be absent from both the Desoto/ Glades and Myakka prairie regions. Within the dry prairie landscape Hypericum edisonianum is restricted to the Desoto/Glades region. A few other species somewhat differentiate between prairie regions; however, most occur in other habitats in the counties where they are absent or nearly absent from dry prairie. The Kiss- immee River region prairie hammocks are the only hammocks surveyed that have Myrcianthes fragrans and Muhlenbergia schreberi. In all prairie regions combined, 302 species were found in dry-mesic to wet-mesic prairies, 391 species in wet prairies, 188 species in depression marshes, 197 species in prairie hammocks, 116 species in swamps and marshes, and 75 species in sub-xeric scrubby prairies. Many taxa differentiate between community classes and types within the dry prairie landscape. The prairie flora of Florida dry prairie is compared to that of coastal prairies in southwest Louisiana and tallgrass prairie in Kansas. Our floristic data suggest that the Florida dry prairie/pineland landscape should be recognized as a distinct floristic region, geo- graphically confined to portions of south-central Florida. INTRODUCTION west-central, and central Florida with its seasonal (winter drought) subtropical climate. Work on the presettlement extent of the Florida dry Florida Dry Prairie Landscape prairie landscape has resulted in delineation of three dry prairie regions (Orzell and Bridges 1999, Bridges 2001, Florida dry prairie is a pyrogenic landscape found Bridges 2006). These are: 1) the “Kissimmee River Prai- only in peninsular Florida, which historically covered ap- 2 2 rie” centered on the lower Kissimmee River, within parts proximately 5,000 km (1,931 mi ). Perennial warm-sea- of Okeechobee, Osceola, Polk, Highlands, and Glades son C4 bunch grasses, rhizomatous evergreen low shrubs, counties; 2) the “Big Prairie” of Desoto County and adja- and decumbent palms dominate this low shrub-grass- cent Charlotte, Hardee, Highlands, and Glades counties; land, dry to wet continuum of plant communities devel- and 3) the “Myakka Prairie,” a smaller area on the Mana- oped on poorly-drained uplands. Depression ponds/ tee/Sarasota county border. Many of the prairie bound- marshes, palm-hardwood hammocks, elevated scrubby aries were originally delineated on presettlement land sandy rises, pine “islands” (in areas with natural fire pro- surveys and historical maps. tection), and seasonally wet herbaceous-dominated drainages are also part of the Florida dry prairie land- Floristic Efforts scape. Dry prairies occur on nutrient-poor sands (spodo- sols) and sandy clays (alfisols) within the Okeechobee, Perhaps the first account detailing common species of Osceola, and Desoto Plains on inter-drainage flats with Florida dry prairie was by Harper (1927), who, based on fewer barriers to lightning-ignited fires than in the pine cursory observations, compiled a list of the most common savanna-flatwoods/pond cypress depression landscape of species of dry prairie and a list of the most common trees central Florida (Orzell and Bridges 1999). Historically and shrubs of other communities within the dry prairie the dry prairie landscape occupied parts of south-central, landscape. Other early accounts of the Florida dry prairie Land of Fire and Water: The Florida Dry Prairie Ecosystem. Proceedings of the Florida Dry Prairie Conference. Reed F. Noss, editor. 2006. 64 vegetation (not floristics) are given in Harshberger (1914) ristic lists were compiled by prairie type (dry-mesic, and Davis (1943). Florida dry prairie has been called pal- mesic, wet-mesic, and wet prairie) (Orzell and Bridges metto prairie (Kuchler 1964 [Kuchler Type K079], Huck 1999, Bridges 2006). Multiple site visits were made to as- 1987, Crumpacker et al. 1988, Sullivan 1994), palmetto sess seasonal floristic differences. When species identifi- grasslands (Grossman et al. 1994), Florida grasslands cations were doubtful, or when it was known that a (Frost et al. 1986), pineland three-awn range (Sullivan species was “new” to a county based on Wunderlin et al. 1994), Florida dry prairie (Grossman et al. 1994, Weakley (1996), we usually collected voucher specimens. Other- et al. 1996), wiregrass prairies, or South Florida flatwoods wise, field identifications were verified by one or both of with “few, if any trees” (Soil Conservation Service 1989). the authors. Special effort was made to achieve nomen- Weakley et al. (1996) classify Florida dry prairie as a Serenoa clatural and taxonomic consistency when compiling com- repens/Aristida beyrichiana upland shrub herbaceous com- prehensive lists from both older reliable checklists (i.e., munity type. General vegetation descriptions are in Cole et al. 1994a, 1994b, Huffman and Judd 1998, Orzell Fitzgerald and Tanner (1992) and Abrahamson and Har- and Bridges 1999) and floristic lists generated in the field nett (1990). Following Harper (1927) relatively few bota- by the authors. With some exceptions, nomenclature fol- nists or ecologists ventured into the dry prairie region for lows that of Wunderlin (1998). Floristic data was com- the next 50 years, perhaps due to its relative remoteness. piled from 291 sites in nine south-central peninsular Long et al. (1969) recognized dry prairie with 69 taxa (but Florida counties. Floristic lists based upon field inventory does not list them) as one of 13 major plant associations in and compilation from reliable sources totaled 11,250 site- southern Florida (Long 1974). It was not until the 1990s specific and community type-specific observations. Most that a resurgence of interest in Florida dry prairie oc- study sites were within Avon Park Air Force Range, Three curred, accompanied by floristic and vegetation studies. Lakes Wildlife Management Area, Kissimmee Prairie Pre- The first study was from a small site in Hardee County that serve State Park, Myakka River State Park, and private seems to include only dry and dry-mesic examples of Flor- lands that permitted us access (Fig. 1). The flora of pine ida dry prairie and some disturbed areas (Cole et al. 1994a, islands within the Florida dry prairie landscape was not 1994b). In a published flora of Myakka River State Park, included in this study. Huffman and Judd (1998) recognize Florida dry prairie With 11,250 records it was possible to compare the and indicate those species known from dry prairie. They composition of communities of the dry prairie landscape also indicated which species occurred in “wetter dry-prai- by the six community type classes (dry prairies, wet prai- rie sites” and in disturbed examples of dry prairie. This re- ries, depression marshes, prairie hammocks, swamps and mains the most comprehensive published floristic study in marshes, and sub-xeric scrubby prairies) and by the three the dry prairie region. The known dry prairie floristic com- regions (Kissimmee River region, Desoto/Glades “Big position as of 1999 was compiled as part of an ecosystem- Prairie” region, and Myakka region). Percent frequency level assessment of dry prairie by Orzell and Bridges of occurrence was calculated by community type class and (1999); however, at that time there were still no specifically by region, and patterns of variation were assessed. documented dry prairie floristic lists from the Desoto Plain Floristic data from the published floras of coastal prai- and few from other parts of the Florida dry prairie region. ries in southwestern Louisiana (Allen et al. 2001) and the This paper updates the floristic tables published in Orzell tallgrass prairie of Kansas (Towne 2002) were compared to and Bridges (1999). the flora of the Florida dry prairie landscape. Microsoft Ac- Although Florida has some of the most extensive re- cess database tables and Microsoft Excel spreadsheets were maining areas of native prairie in the southeastern United constructed to compare the prairie element subsets of States (DeSelm and Murdock 1993), high-quality prairie is these floras to the dry prairie subset of the Florida dry prai- still being converted,