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Vascular Flora of Powhatan County, Virginia

Powhatan County is a largely rural county of the Virginia piedmont currently experiencing exurban development pressure. Commercial pine forests occupy much of the land area; most natural vegetation occurs in various hardwood forests. Plant life is supported largely by soils derived from Proterozoic to Paleozoic metamorphic and igneous rocks, soils developed over Triassic basins, and riparian soils associated with the James and Appomattox Rivers. The annotated checklist is based on new collections gathered between September 2003 and August 2005, supplemented with records from regional herbaria and the Atlas of the Virginia Flora. Field work sampled at least 12 distinct community groups recognized in Virginia. The checklist contains 1020 taxa (1013 species, 515 genera, and 146 families). Twenty-one percent of the species are naturalized introductions. Twenty five species (2.5% of the total) are of conservation concern, and 118 collections (12% of the total) represent new records for Powhatan County. INTRODUCTION Powhatan County is a largely rural county in the piedmont region of Virginia that is currently experiencing significant exurban development pressure. Although its plants are reasonably well represented in regional herbarium collections, no previous county-wide floristic inventory exists. There is, however, one published list of plants for the Jones and Mill Creek watershed region (Corcoran 1981). Given its current rapid growth and concomitant loss of habitat and potential loss of biodiversity, we resolved to enumerate a comprehensive and contemporary inventory of the native and naturalized plants of Powhatan County. We accumulated records of plant occurrence in the county by means of three distinct yet mutually supportive strategies: 1) field work and collection of new herbarium specimens, 2) complementary herbarium studies to locate additional records of taxa previously collected by other botanists, and 3) gleaning of further records from the Atlas of Virginia Flora (Harvill et al. 1992, Virginia Botanical Associates 2005). The past decade and a half has been a vibrant time for systematic botany as molecular data and cladistic analyses have transformed many long-held concepts of the natural relationships among plants (Chase 2005). The impact has been felt at all levels of the taxonomic hierarchy in terms of both taxon composition and nomenclature. Thus, although the flora of eastern North America is, generally, very well known, no published floras and few regional inventories reflect contemporary taxonomic concepts. In our attempt to produce a ‘‘modern’’ inventory reflecting contemporary taxonomic concepts, we relied heavily on the ongoing efforts by Alan Weakley (2002, 2005) to revise the floras of Virginia and the Carolinas. We trust that our inventory of Powhatan County plants will contribute in reciprocal fashion to the documentation of Virginia flora. Further, an ancillary goal of this study is to interpret the plant life of Powhatan County in terms of the vegetationbased ecological communities that have been defined by Fleming et al. (2004). Geography and Land Use Powhatan County (Figure 1) is bounded on the north by the James River, on the south by the Appomattox River, on the east by Chesterfield County, and on the west by Cumberland County. The county seat is located approximately 56 km west of the city of Richmond. Although growth is occurring throughout the county, pressure from development is greatest in the eastern portion, reflecting the influence of Richmond, Chesterfield County, and the recent completion of a major new highway (route 288) that passes through the northeastern corner of the county. Powhatan County has an area of about 438 sq. km, or 71,000 ha (United States Department of Agriculture 1988). Following the classification adopted by Fleming et al. (2004), Powhatan County is part of the southern piedmont physiographic province of Virginia. The county’s northern boundary, the James River, is also the boundary between the northern and southern physiographic provinces of the state. Given its near-central position, Powhatan County is reasonably typical of the piedmont region of Virginia which, overall, represents *email address: jhayden@richmond.edu Received February 2, 2006; Accepted December 27, 2006. CASTANEA 72(3): 138–158. SEPTEMBER 2007 138 Castanea Volume 72 approximately 41% of the land area of the commonwealth (Virginia Department of Forestry 2005). Terrain of Powhatan County may be characterized as a gently sloping plateau of modest altitude, dissected by numerous small streams which empty into either the Appomattox River to the south or the James River to the north. The highest point in the county is 150 m above sea level in the north central portion, and the lowest point is about 37 m above sea level in the easternmost section. Commercial forestry and farming have long been the chief land uses in the county but suburban development is an increasingly important economic engine. Cultivated crops cover about 9 percent of the county and pasture, about 10 percent. Commercial forest covers at least three-fourths of the county. The largest tracts of contiguous forest (4,000–20,000 ha) are found in the northwestern portion along the Cumberland County border, in the northern section along the James River, and in the southern section along the Appomattox River. Most of the forested land is mixed hardwood or plantation pine forest (Virginia Department of Forestry 2005). The main roadways are: US route 60, which in its east-west course bisects the county along the divide between the James and Appomattox watersheds; state route 711, which runs eastwest in the northern section; state route 522, which runs north-south between the James River and route 60; and route 288 in the northeast corner of the county (Figure 1).