The Vascular Flora of the Tallgrass Prairie Preserve, Osage County, Oklahoma

The 15,410 ha Tallgrass Prairie Preserve (Osage County, Oklahoma), managed by The Nature Conservancy, consists of a variety of grassland, forested, wetland, and disturbed habitats. 1,612 specimens of vascular plants collected between 1992 and 2007 were examined to obtain a vouchered flora of the preserve. The known flora consists of 763 species in 411 genera and 109 families. 12.1% of the species are not native to North America. INTRODUCTION The Nature Conservancy has owned and managed the Tallgrass Prairie Preserve (hereafter TGPP) in Osage County, Oklahoma, since 1989. The guiding principle for management of the preserve is to recreate a semi-natural grazing and disturbance regime, with bison herds and a stochastic fire regime (Hamilton 1996). Because of its large size and varied habitat, the TGPP is an ideal location for ecological, environmental, and taxonomic research (Palmer et al. 2000). The purpose of this paper is to present a checklist of the vascular flora of the TGPP, both to assist research and to serve as a baseline inventory in case management results in floristic changes. THE TALLGRASS PRAIRIE PRESERVE The TGPP is a single 15,410 ha parcel of land (but with a few small inholdings) located between 36.73u and 36.90uN latitude, and 96.32u and 96.49uW longitude. The preserve encompasses almost the entire watershed of Sand Creek, and elevation ranges between 253 m, where Sand Creek leaves the TGPP in the SE, and 366 m in the plateau in the northwestern part of the TGPP. Although most of the terrain is gently undulating, there are a several rocky bluffs (both sandstone and limestone), mostly bordering major creek valleys (Sand Creek, Wild Hog Creek, and Little Sand Creek). Limestone and sandstone are frequently on the surface, sometimes alternating in very close proximity. Shale is only visible in stream banks, and substantial areas of alluvium only occur along Sand Creek and Little Sand Creek. Approximately 90% of the TGPP consists of grasslands. The majority of these grasslands are tallgrass prairie (with Andropogon gerardii, Sorghastrum nutans, Sporobolus compositus, Panicum virgatum, and Schizachyrium scoparium dominating), but shortgrass prairies (dominated by Bouteloua dactyloides and B. hirsuta) occur in ‘grazing lawns’ and in shallow soils. Most of the forested areas are crosstimbers (dominated by Quercus stellata and Quercus marilandica) but there are substantial areas of floodplain forests, and mesic to xeric hardwood forests on the upper stream terraces above Sand Creek. Many of the minor tributaries of Sand Creek have been impounded by humans, beavers, or both – leading to a diversity of wetland habitat types. Seasonal wetlands in wallow-like depressions (Coppedge and Shaw 2000) frequent many portions of the preserve. Anthropogenic habitats near roads, dwellings, utility buildings, cattle pens, abandoned barns, etc. contribute substantially to the flora (especially with respect to exotic species). Further information about the management objectives of the preserve are in Hamilton (1996) and a brief description of research projects at the preserve is in Palmer et al. (2000). METHODS The compilation of species lists is an intrinsically subjective exercise (Palmer 1995, Palmer et al. 2002, Fridley et al. 2006) because it involves the intentional seeking of unusual or interesting habitats. Between 1992 and 2001, I visited as many habitats as *email address: [email protected] Received September 12, 2006; Accepted February 7, 2007. CASTANEA 72(4): 235–246. DECEMBER 2007