Growth of the rare southern appalachian endemic plant houstonia montana (Rubiaceae) in contrasting habitat types1

Abstract

Abstract We examined the ability of Houstonia montana, a rare plant endemic to the Southern Appalachians, to grow in two markedly different habitat types. Most known populations of H. montana occur on rock outcrops with little soil development and sparse vegetation. In contrast, a few populations occur on grassy slopes with continuous soils and dense surrounding vegetation. We compared growth and life-history traits of two rock-outcrop and two grassy-slope populations. Houstonia montana was a dominant vascular plant species in all four sites, with 20–37 % ground cover on grassy slopes and 4–6% on rock outcrops. Growth began earlier in the season and plants were taller on grassy slopes than on rock outcrops. In contrast, reproductive potential, numbers of leaves, and ratios of leaves:height were markedly higher in one grassy slope site but showed no consistent pattern between habitats. Foliar nitrogen:phosphorus ratios varied widely and indicated N limitation in at least one grassy slope site and P limitat...