Do Changes in Stream Physiochemistry and Landsuse Explain Appalachian Elktoe (Alasmidonta raveliana Declines in Western North Carolina?
The Appalachian elktoe mussel, Alasmidonta raveneliana , is endemic to upper Tennessee River Drainage streams draining the Blue Ridge Physiographic Province in North Carolina and Tennessee. Recently, Appalachian elktoe populations in some Western North Carolina streams have undergone dramatic, yet enigmatic declines and few parsimonious mechanisms have been proposed to explain the near complete extirpation of this already rare mussel from its key strongholds in high-quality streams. We used 40+ years of historic water quality data from EPA’s Storet database to examine temporal changes in temperature, specific conductance, pH, nitrate and dissolved oxygen in 10 streams supporting A. raveneliana populations. In two streams that have seen recent A. raveneliana declines, the Little Tennessee and the North Toe River, we observed significant increases in summer and early spring temperatures. These trends were generally absent from streams with stable A. raveneliana populations, although the Tuckasegee River where the largest known A. raveneliana population currently resides, exhibited significant warming in 6 of 12 months across a 35+ year time span possibly foretelling the eventual collapse of this population. Examination of land use variation over the past 20+ years is ongoing but data suggest that heavily forested watersheds, such as the South Toe, may become key habitat strongholds for this already declining species.
83 • Michael Perkins1, Michael M. Gangloff1, Nathan Hjohnson2
Phylogeny of the Critically Endangered North American Spinymussels
The spinymussels (Unionidae: Elliptio steinstansana, Elliptio spinosa, and Pleurobema collina) are critically endangered and endemic to the Southeastern Atlantic Slope. Although often characterized by the presence of conspicuous external spines, the spinymussels continue to be a source of taxonomic confusion. Key diagnostic features within the Pleurobemini (Elliptio and Pleurobema) are notoriously plastic, and at least two of the spinymussels (E. steinstansana and P. collina) share remarkably similar life history traits. Molecular analyses could improve characterization of these species, however genetic data is severely limited. We sequenced a ~1100 bp fragment of combined ND1 and COI mtDNA regions from Tar (E. steinstansana n=22), Altamaha (E. spinosa n=8), and James (P. collina n=55) spiny mussels using standard Sanger techniques. Preliminary phylogenetic analyses suggest E. steinstansana and P. collina form a distinct clade separate from any known Elliptio or Pleurobema taxa and likely warrant recognition as a new genus. Furthermore, these species are very closely related and may be conspecifics. Additionally, E. spinosa forms a clade separate from Elliptio and may constitute a monotypic genus. These preliminary results suggest a need to revise both taxonomic and evolutionary paradigms for these taxa. Ongoing research (Spring 2014) will develop microsatellite markers for E. steinstansana and P. collina. The results of this research will provide conservation agencies with data needed to refine and develop more effective population management strategies for these threatened taxa.
1 Dept of Biology, Appalachian State University, Boone, NC; 2 United States geological Survey, Gaineville, FL
84 • Richard M. Wooten1, Anne C. Witt2, Chelcy F. Miniat3, Tristram C. Hales4, Jennifer L. Aldred5
Frequency and Magnitude of Selected Historical Landslide Events in the Southern Appalachian Highlands of North Carolina and Virginia: Their Relationships to Rainfall, Geologic and Geomorphic Settings, Ecohydrological Controls, and Their Resulting Effects on Forest Structure
Landsliding is a recurring process of mass wasting and sediment transport in landscape evolution in the Southern Appalachian Highlands (SAH). Debris flows, dominant among landslide processes in the Blue Ridge of North Carolina and Virginia, are triggered when rainfall creates excess pore-water pressures in steep, soil-mantled slopes. Rainfall from tropical and extra-tropical cyclones triggered hundreds to thousands of debris flows in 1916(NC), 1940(NC), 1969(VA), 1977(NC) and 2004 NC); whereas rainfall from other more localized storms in these and other years triggered tens to hundreds of debris flows. The orographic enhancement of rainfall combined with geologic and geomorphic characteristics makes certain landforms prone to debris flows. Field and GIS studies have helped quantify the magnitude of major debris flow events that have caused loss of life and property, and severely affected forest lands. Debris flows alter forest structure and hydrology by creating canopy gaps and disrupting aquatic ecosystems. Forest cover is an important stabilizing factor through precipitation interception, evapotranspiration, and root reinforcement. Root reinforcement reflects hillslope-scale differences in below ground biomass and tensile strength, and is directly affected by precipitation and soil moisture. Studies in SAH woody species show feed-forward responses of root tensile strength to changes in precipitation and soil moisture. Roots are weaker in convergent compared to divergent geomorphic features, and roots in wetter soils, i.e., after rain events, become weaker compared to when soils are drier. Thus, there is a feed-forward process in precipitation (and therefore soil moisture), root strength changes, and debris flow hazards.
1 North Carolina Geological Survey, Swannanoa, NC; 2Virginia Dept of Mines, Minerals and Energy, Division of Geology and Mineral Resources, Charlottesville, VA; 3 Coweeta Hydrologic Lab; Center for Forest Watershed Research; USDA Forest Service, Southern Research Station, Otto, NC; 4 School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK; 5 Dept of Geography & Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC
