Riverscour communities are narrow, open communities, maintained by flooding, associated with rocky riparian zones on the banks of high-gradient rivers. These disjunct naturally open areas, dominated by graminoids, herbs, and shrubs, have an insular distribution and harbor rare, endemic, disjunct, and undescribed species. The Caney Fork River of Tennessee has significant areas of riverscour. Its Highland Rim portions contain the largest area of limestone riverscour in the Southeast; sandstone riverscour of its Cumberland Plateau portion has populations of the rare Conradina verticillata and Spiraea virginiana. While sandstone riverscour communities have received some study, limestone riverscour has been poorly documented. The objectives of this study are to 1) document the vascular flora and 2) community associations of Caney Fork riverscour and 3) use these data to develop hypotheses about the biogeography of Caney Fork riverscour. Using aerial photography, study sites in each of two ecoregions were chosen: Rock Island State Park (Warren/White County-Highland Rim) and Scott’s Gulf (White County-Cumberland Plateau). Since 2012, 224 species were collected from these sites representing 162 genera and 71 families. Twelve rare species were documented, including three state records (Apocynum sibiricum, Phyllanthopsis phyllanthoides, Symphyotrichum pilosum var. pringlei). The communities associated with limestone riverscour included limestone seeps, pools, glades and boulder bars. Sandstone communities included sand, cobble, and boulder bars. Plot sampling will be conducted in 2014 to further characterize the vegetation associations. This study provides baseline data for riverscour communities that will be compared with other studies of Southeastern riverscour.
Challenges in Properly Identifying Species of Rhododendron (Ericaceae) in South Carolina
A taxonomic understanding of the genus Rhododendron (Ericaceae) in the southeast continues to change. Two new species have been described in the last 15 years. Toward attempting to clarify the number of species present, my work relates to axonomy in South Carolina (SC). Flowering individuals are readily identifiable, but a challenge with vegetative material. My goal is to identify material year round, including flowers (spring), fruits (summer) or flower buds (fall or winter). Variable morphological features add a challenge for identification. Two species that intergrade relative to features of bud scale surface hairs and marginal glands are canescens and periclymenoides. Field work has shown variation between populations and even within populations. A second challenge is in clarifying species over their geographical range. As an example, the minus complex appears to be represented by one species in SC. However, carolinianum, a cryptic segregate species known from higher elevations of North Carolina and Georgia is speculated to occur in SC. A third challenge has been in the recognition and identification of hybrids. Literature reports commonly include parental species involved in hybrids, yet definitive morphological features to recognize such have not been well documented. Hybrid individuals are recognized by some as having increased number of flowers per bud, unusual perianth colors, and intermediate pubescence patterns. Lastly, there are problems of using herbarium specimens, as they commonly lack macro scale features such as habit and population variation.
Biology Dept, Newberry College, Newberry, SC
94 • Jamie D. Smith, Conley K. McMullen
The Relationship Between Riparian Zone Width and Floristic Quality Along Streams in Shenandoah County, Virginia
Riparian zones harbor an above average plant biodiversity. This biodiversity is increasingly threatened by invasive species and human disturbance such as deforestation from agriculture and urban development. This study will determine the relationship between the size of the riparian zone and the floristic quality of its vegetation. A bioassessment tool, which utilizes plant community characteristics will, be used to obtain an estimate of habitat quality. This estimate, in turn will determine whether larger riparian zones provide more protection from the impacts of disturbance and provide higher quality habitats for plants. Vegetation plot data is currently being processed from five streams in Shenandoah County, Virginia
Classification of the Distribution Patterns of Plant Taxa Occurring in the Unglaciated Southeastern United States
Numerical classification has been used to identify and delineate groups of plants occurring together in the same physical location (plots), a basis for vegetation ecology community types. The approach uses repeated co-occurrence patterns of plants within plots to define vegetation types. These analytical tools can also be used on a regional scale to group plant taxa into distinct chorotypes, or repeated distribution and abundance patterns of taxa. Chorotype analysis is more commonly employed outside North America and for animal taxa. The goal of this presentation is to determine the number and extent of phytogeographic patterns (chorotypes) via hierarchical clustering and non-hierarchical partitioning. Our analysis includes approximately 7,000 plant taxa present in the unglaciated Southeastern United States, with their complete distribution and abundance patterns at the state - physiographic province scale. Each chorotype is defined in terms of the frequency of occurrence in each geographic unit (whether only one, several, up to all units), and the best fitting plant taxa occurring within the chorotype. We provide some initial and coarse-scale interpretation of the environmental and historical processes contributing to the existence of the patterns.
Dept of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
