TRENDS IN VEGETATION RECOVERY OF THE KINSEY RUN DEBRIS FAN, MADISON COUNTY, VIRGINIA

A catastrophic storm that struck the central Virginian Blue Ridge Mountains in June, 1995 delivered over 770 mm (30 inches) of rain in 16 hours. The deluge triggered more than 1,000 slope failures, and deeply incised stream channels and debris fans. Debris flows traveling at velocities up to 24 m/s (53 mph) stripped away vegetation on numerous surfaces. At the Kinsey Run debris fan near Graves Mill, flows removed nearly all woody vegetation in their paths for 2 km. The fan is located in the Shenandoah National Park and has remained undisturbed since the storm. This study measures trends of vegetation reestablishment over the last six years. Recovery rates were analyzed at four 100 m2 plots evenly spaced along the longitudinal axis of the fan, and compared to a control site proximal to the disturbed fan. Unpublished data indicate pioneer species, including black locust, great mullein, tree-of-heaven, and lesser amounts of gymnosperms and paulownia, were the dominant woody species to first reestablish growth on the fan following the 1995 storm. Currently, virginia pine, tulip poplar, sycamore, birch, and dogwood are competing with the pioneer species in the study area. At Kinsey Run, biodiversity and plant succession rates, characterized by the number of trees per plot, tree diameter, and height, depend on the factors of seed availability and sapling competitiveness. These factors are functions of water availability, soil texture, elevation, and minimum distance to undisturbed areas. Preliminary analysis of the data shows a moderate correlation between the number of pioneer species at a given site and the site’s distance from undisturbed areas (R2=0.68). Factors of water availability and soil texture show weaker correlations with pioneer species counts. This research is part of a longer-term study that is documenting plant reestablishment and succession following disturbances by debris flows and catastrophic flooding in the central Virginian Blue Ridge Mountains.