ALGIFIC (COLD-AIR PRODUCING) TALUS AT ICE MOUNTAIN, WEST VIRGINIA, USA: STRUCTURE AND DYNAMICS OF A RARE CENTRAL APPALACHIAN ECOLOGICAL REFUGIUM

Cold-air flowing from the base of the Ice Mountain talus at ~235 m above sea level supports 5 rare plant species not known below 900 m elevation elsewhere in the Central Appalachians. Cold-air flowing from the talus maintains a paleo-refugium that may have operated without significant interruption for 10,000 years. Other Central Appalachian algific talus localities were noted historically, but have been destroyed through ice mining or other human activities.

A multi-faceted geophysical and geological study of the talus reveals an unremarkable stratigraphy in which 1-2 m diameter sandstone blocks lie unconformably on impermeable Devonian shale bedrock. Terrain conductivity and Very Low Frequency electromagnetic surveys indicate ~8 m talus depth and possible perennial ice lenses at the talus-bedrock contact. Talus morphology is unusual in that a general concave profile has been undercut by North River, giving a steep convex profile for the lower 30 m of the slope. Most of the talus is bare of soil and vegetation, except crustose lichen. The steeper lower talus is mostly vegetated, with a discontinuous organic mat broken by 25-50 cold-air vents. The upper and middle talus has numerous openings that allow air in or out of the talus. The openings on the lower slope range from 0.01 to 1 sq m; hence the total cold-air vent cross-sectional area is a tiny fraction of the total area of openings on the concave slope above.

Air drains from algific vents whenever talus air temperature is less than outside air temperature at the toe of the slope. Cold air drainage is nearly continuous, with temperatures observed from -6.5 to +9.0 degrees C. A northwest aspect precludes direct sun on the talus, except for late afternoons in spring and summer. Snow and other precipitation infiltrating into the talus may further moderate temperatures during subsequent warm weather. The slope functions as a unidirectional cold air sink. Warm air may rise out of the upper and middle talus, but there is insufficient vent surface area to allow either complete drainage of cold air from the talus or entry of warm air rising from the valley.

This study suggests that loss of lower-talus vegetation or widening of existing vents would imperil the algific talus ecosystem and that historical algific slopes can be restored through revegetation and vent constriction.