Exceptional Diversity in the Vascular Flora of the Holston Army Ammunition Plant, Hawkins County, Tennessee

The Holston Army Ammunition Plant in the Ridge and Valley physiographic province of Hawkins County, Tennessee, comprises 2,420 ha encompassing 11 river kilometers of the Holston River and rising to the crest of Holston River Mountain. The extreme physiographic diversity includes riparian and bottomland areas, wetlands, grasslands, calcareous knobs, karst, and mountain slopes, with soils varying from acidic to neutral and from fine to coarse grained. Plant communities vary from largely intact natural communities to highly impacted open areas. The vascular flora of the site was composed of 1,047 species and subspecific taxa distributed in 140 plant families and including 458 county records and 207 exotics. The four most diverse plant families were the Asteraceae (131 taxa), Poaceae (126 taxa), Cyperaceae (87 taxa), and Fabaceae (51 taxa). The number of taxa in the four largest plant families far exceeded the number predicted by species-area plots. Eleven species are state-listed; two species were new to Tennessee. Noteworthy plant communities were associated with old growth Quercus montana, forested mid-slope plateaus, and grasslands dominated by native grasses and rushes. Many taxa had geographic affinities to areas to the south and west and fewer had affinities to the north.