CASTANEA 69(2): 116–124. JUNE 2004 Vascular Flora of a Southern Appalachian Fen and Floodplain Complex 1 1 2 ROBERT J. WARREN II, *J.DAN PITTILLO, and IRENE M. ROSSELL 1Department of Biology, Western Carolina University, Cullowhee, North Carolina 28723-9646; 2Environmental Studies Department, University of North Carolina at Asheville, Asheville, North Carolina 28804-3299 ABSTRACT A survey of vascular flora was completed at wetland sites in the Tulula Creek floodplain in Graham County, North Carolina as part of a comprehensive ecological study. The vegetation survey was conducted in forested and unforested fen and floodplain wetlands in 1994 and 2001, and in a forested floodplain wetland in 2001 in order to document plant species occurring in these rare mountain habitats. A total of 107 taxa representing 52 families were identified. More than 66% of the taxa also have been reported in other non- alluvial wetlands in the region; about 31% of the taxa identified in the Tulula Creek wetland complex have been reported in non-alluvial wetlands in West Virginia and about 12% have been reported in the non- alluvial wetlands of northeastern United States and adjacent Canada. This paper documented the vascular plant communities within this rare wetland complex before intensive stream restoration began in 2001. INTRODUCTION Wetland plant communities in the Southern Blue Ridge Province are uncommon ecological islands within an expansive temperate deciduous forest; they often contain plant species that do not occur in the surrounding terrestrial and fluvial habitats (Weakley and Schafale 1994). Non-alluvial southern Appalachian wetlands are found in every mountain county in North Carolina (Weakley and Schafale 1994), yet they are infrequent ecosystems that cover less than one percent of the land area (Pittillo 1994). While it is unlikely that wetlands were ever extensive in the mountain areas, only about 200–300 ha of an estimated 2,000 ha of southern mountain wetlands remain in North Carolina (Weakley and Schafale 1994, Moorhead and Rossell 1998). There has been considerable debate over whether southern Appalachian wetlands should be classified as fens or bogs. The criteria used to distinguish fens and bogs in northern regions (Heinselmann 1970, Moore and Bellamy 1974) do not fit the southern ecosystems well. Generally, northern bogs are described as ombrotrophic, acidic (pH , 4.1) wetlands with a surface layer of sphagnum (Sphagnum spp.) and other mosses, and with hydrology and ion input influenced primarily by precipitation. True ombrotrophic bogs develop peat layers higher than their surroundings and receive nutrients and other minerals exclusively from precipitation (Mitsch and Gosselink 2000). In contrast, northern fens are peatlands with hydrology derived from groundwater that has passed through mineral soil (minerotrophic), and often they are dominated by sedges (Moorhead and Rossell 1998). Many southern mountain wetlands have characteristics of both fens and bogs. Most, if not all, receive groundwater input, in addition to precipitation and surface inflow (Moorhead and Rossell 1998, Moorhead et al. 2001). Unlike the mineral soils of northern Europe and northern North America, which contain high levels of cations such as calcium and magnesium, the moun- tains of the southern Blue Ridge contain highly weathered, leached soils over nutrient-poor, * email address: [email protected] 116 CASTANEA VOLUME 69 highly resistant bedrock. The long-term interactions of climate, topography and vegetation on these materials has produced regional soil complexes that are generally acidic and nutrient poor (Richardson and Gibbons 1993, Weakley and Schafale 1994, Pittillo et al. 1998). Wetlands associated with the southern end of the Appalachian Mountains (North Carolina and Tennessee) usually contain mineral soils with a lower organic matter concentration (7–40% of dry mass) and higher pH than their more northern counterparts in West Virginia (Wieder 1985, Walbridge 1994, Mowbray and Schlesinger 1988, Stewart and Nilson 1993, Moorhead and Rossell 1998, Moorhead et al. 2000). While the soil chemistry of most southern Appalachian wetlands more closely resembles northern bogs than fens, they lack the deep peat deposits, probably due to the warmer southern climate and longer dry periods during the growing season (Clymo 1984; Winston 1994; Wieder et al. 1989, 1994; Moorhead and Rossell 1998). Since they receive groundwater inputs from surrounding mineral soils, with the degree of minerotrophy varying from rich to poor, the authors propose ‘‘southern Appalachian fen’’ as the most parsimonious classification. Despite the scarcity of non-alluvial wetlands in the southern Appalachian Mountain region, these small systems contain diverse floral communities with many rare and uncommon species (Murdock 1994, Weakley and Schafale 1994, Moorhead and Rossell 1998, Rossell et al. 1999). Southern Appalachian wetlands contain almost one-fifth of 724 rare plant species monitored by the North Carolina Natural Heritage Program (Murdock 1994); however, pub- lished quantitative vegetation data are sparse. The plant communities of southern Appala- chian wetlands include endemics that exist in the unique microhabitats of the region, as well as species more commonly found in northern and Coastal Plain regions (Richardson and Gibbons 1993, Murdock 1994, Pittillo 1994, Weakley and Schafale 1994). The objective of this study was to inventory and document vascular floral species within Tulula Creek wetland complex. In addition, the wetland indicator status, rare or uncommon status, and the geographic affinity of each species were investigated. DESCRIPTION OF THE STUDY AREA The 83-ha research site is located in the Tulula Creek floodplain (358169000N; 838429000W; elev. 800 m) in Graham County, North Carolina. The large, relatively flat floodplain is a mosaic of forested and unforested wetlands, including small depressions where Sphagnum spp. accumulate. The floodplain gradually intergrades into upland forests. The site is bordered by U.S. 129 and an abandoned railroad grade; it is crossed by two power lines and has clear vestiges of timbering and subsequent white pine (Pinus strobus) planting. However, it remained a wetland of regional significance (Gaddy 1981) until the mid-1980s when the United States Forest Service traded it to developers who planned to build a golf course and housing complex along the floodplain (Rossell et al. 1999, Rossell and Wells 1999, Moorhead et al. 2001). The developers dredged and channelized Tulula Creek, cut drainage ditches into the floodplain and cleared large areas. The project failed, and in 1994 the North Carolina Department of Transportation purchased the wetland for restoration as a wetland mitigation bank (Moorhead et al. 2001). The site is known locally as Tulula Bog, but it is a wetland complex that includes areas of southern Appalachian fen (ombrotrophic), red maple (Acer rubrum) swamp and open meadow (Moorhead and Rossell 1998, Warren 2002). The North Carolina Natural Heritage Program classified the site as a Swamp Forest-Bog Complex (Schafale and Weakley 1990), defined as poorly drained bottomlands with soils of alluvial origin now removed from regular flooding. METHODS Vegetation sampling was conducted in an open canopy fen (open fen), closed canopy fen (closed fen), and an open canopy floodplain (open floodplain) in 1994 and 2001. A fourth site, a closed canopy floodplain (closed floodplain), was sampled in 2001. The two fen sites and the open floodplain adjoin each other, while the closed floodplain is approximately 1,000 m downstream from the other three. The fen receives a steady input of groundwater flow and is JUNE 2004 117 removed from the stream while the floodplain sites are drier and immediately border the stream (Rossell et al. 1999, Rossell and Wells 1999, Moorhead et al. 2001). The 1994 fen sites were selected to investigate the vegetative communities in the forested and unforested portions of the fen, while the floodplain site was chosen for a separate investigation of red maple dynamics. The closed floodplain site was added in 2001 in order to document plant species in a late seral wetland community. A 0.8-ha grid of 100 m2 plots was established in the fen in 1994, with approximately half the plots located within the open canopy area and the other half within the closed canopy area. Twenty plots were randomly selected in each of the open and closed canopy sides of the fen. Trees with a diameter at breast height (DBH) .10 cm were inventoried in 10 3 10 m quadrats. Shrubs and saplings with a 2–10 cm DBH were inventoried in a 4 3 4 m quadrat nested within each 100 m2 plot. Herbaceous vegetation and woody seedlings ,2 cm DBH were inventoried in a 1 3 1m quadrat nested within each 100 m2 plot. The 1 3 1 m and 4 3 4 m quadrats did not overlap. Six 20 3 30 m plots were established in the open floodplain in 1994. Herbaceous vegetation was sampled using the same protocol as in the fen, with the exception that four 1 3 1 m quadrats were randomly placed in each of the six plots rather than in a grid. Shrub-layer and tree-layer vegetation was sampled using a 7 3 7 m (shrub-layer) and a 18 3 18 m (tree-layer) quadrat nested within each of the six plots. The fen and floodplain were re-sampled in 2001. A fourth site, the closed floodplain, was inventoried in 2001 using a 20 3 100 m linear grid of 40, 100 m2 plots. The linear grid was chosen to parallel hydrologic gradients in the floodplain. Vegetation was sampled using the same protocol as in the fen. Plants were identified using Radford et al. (1968) and Weakley (2000). Voucher specimens were deposited at the Western Carolina University Herbarium (WCUH). Uncommon species were categorized based on species status reported in the North Carolina Natural Heritage Program Watch List (Amoroso and Finnegan 2002) and Weakley (2000). A species was defined as having a northern affinity if its geographic range primarily covers northern latitudes but is extended southward via the southern Appalachian Mountains.