Vascular Flora of Red Slough and Grassy Slough Wildlife Management Areas, Gulf Coastal Plain, McCurtain County, Oklahoma, The

Castanea, Dec 2004 by Hoagland, Bruce W, Johnson, Forrest

ABSTRACT

This paper reports the results of an inventory of the vascular plants at the Red Slough and Grassy Slough Wildlife Management Areas in southeastern Oklahoma. A total of 426 taxa of vascular plants in 269 genera and 106 families was collected. The most species were collected from the families Asteraceae (53), Poaceae (42), Cyperaceae (31), and Fabaceae (27). Ninety-nine species were annuals or biennials, and 328 perennials. Ninety-three species of woody plants were present. Twenty-eight species not native to North America were collected representing 6.6% of the flora. Thirty species tracked by the Oklahoma Natural Heritage Inventory were found. The first occurrence in Oklahoma of Anoda cristata, Malvaceae, is reported in this study.

INTRODUCTION

The objective of this study was to provide a baseline floristic inventory for the Red Slough Wildlife Management Area (RSWMA), a bottomland hardwood forest restoration project, and adjacent Grassy Slough Wildlife Management Area (GSWMA). The benefits are twofold. First, both sites are located in southeast Oklahoma, the region of the state with the highest number of rare and sensitive plant species. Therefore, data of conservation value should be gained. secondly, by documenting the current flora, resource managers at both sites will have a tool to monitor changes in species composition.

In May of 1916, H.W. Houghton and G.W. Stevens collected the first known specimens from McuCurtain County, 19 species from the vicinity of Idabel and Shawneetown (Hoagland 2003). Since then, numerous botanists have made collecting forays to McCurtain because of the diverse flora. At present, there are 8,565 specimens of McCurtain County plants in Oklahoma herbaria representing 1,498 species, intraspecific taxa, and hybrids (Hoagland 2003).

Both sites are located in southeastern McCurtain County, Oklahoma (Figure 1). RSWMA (94.616�W to 94.703�W and 33.725�N to 33.755�N) is a 2,158-hectare bottomland hardwood restoration project cooperatively managed by the United States Forest Service, Natural Resources Conservation Service, and Oklahoma Department of Wildlife Conservation. Land acquisition began in 1996 (United States Forest Service 2003). Elevation ranges from 100.3 m to 104.2 m. The second site, GSWMA (94.743�W to 94.761�W and 33.779�N to 33.799�N), is located approximately 4 kilometers west of RSWMA and encompasses 264 hectares (Smith 2003). Elevation ranges from 105.4 m to 112.8 m.

The physical environment of both sites is similar. Both are located within the Subtropical Humid (Cf) climate zone (Trewartha 1968). Summers are warm (mean July temperature = 26.9�C) and humid, and winters are relatively short and mild (mean January temperature = 4.0�C).

Mean annual precipitation is 136 cm (Oklahoma Climatological Survey 2003). Physiographically, the study area is located on the Upper Gulf Coastal Plain (Hunt 1974) and within the Dissected Coastal Plain province of Oklahoma (Curtis and Ham 1979). The surface geology is predominantly Quaternary alluvial deposits consisting of silt, sand, clay, and gravels on floodplains and terraces of the Red River. North of the RSWMA, the geology is Cretaceous nonmarine sand and clay and marine limestone and clay (Branson and Johnson 1979). Two soil associations occur at RSWMA and GSWMA. The Kinta-Wrightsville association occurs on uplands and terraces along the Red River. These soils are deep, nearly level, poorly drained loamy soils. The Pledger-Roebuck-Redlake Association is composed of deep, nearly level, moderately to poorly drained clayey floodplain soils (Reasoner 1974). Potential natural vegetation at both sites falls within the bottomland forest category of Duck and Fletcher (1943). Bottomland forests were cleared in the mid-nineteenth for agricultural production, including rice at RSWMA. Oldfields and second growth bottomland forests predominate throughout the study area.

METHODS

Collection sites were selected following a review of United States Geological Survey 1:24,000 topographic maps and field reconnaissance. The predominant vegetation association at these sites was classified according to Hoagland (2000). Eleven collection sites were established for intensive floristic sampling. However, collecting was not restricted to these sites and previously uncollected species were gathered wherever they were encountered. Collections were made from March through October 1999. Vouchers for species not native to North America (exotic) were made from naturalized populations only, thus excluding cultivated and ornamental plants. Specimens were processed at the Robert Bebb Herbarium of the University of Oklahoma (OKL) following standard procedures. Manuals used for specimen identification included Waterfall (1973), Diggs et al. (1999), and Yatsievych (1999). Abundance of each species was ranked on a scale of 1-5; 1 being the rarest or least abundant and 5 being dominant (Palmer et al. 1995). The Oklahoma Natural Heritage Inventory (2003) Working List of rare Oklahoma Plants species was reviewed to determine the conservation status of plants at RSWMA and GSWMA. In the list, species are ranked according to level of imperilment at the state (S) and global (G) levels on a scale of 1-5; 1 representing a species that is imperiled and 5 one that is secure (Groves et al. 1995). Origin, whether native to introduced to North America, was determined using Taylor and Taylor (1991) and the United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS 2003). Nomenclature follows USDA-NRCS (2003). Voucher specimens were deposited at OKL.