Botanists have studied the origin and maintenance of southern Appalachian grassy balds for at least the last century. Grassy balds are treeless areas, unique to the southern Appalachian Mountains that exist below the physiological treeline. Historically the focus of research in balds was that of their origin and the mechanism(s) that led to bald persistence. More recently it has become apparent that these areas are in fact undergoing secondary succession and may be lost without management. However, succession in these areas has rarely been documented over extended periods. The objective of this study was to monitor invasion of Fraser fir (Abies fraseri) and red spruce (Picea rubens) into a grassy bald. The study site was the Judaculla Fields located on the southwestern slopes of Richland Balsam Mountain, along the Blue Ridge Parkway, NC. Four permanent plots (5 by 6 m) that contained tree seedlings were selected in 1979 as part of a broader study on seed dispersal into the bald. Fifteen subplots were sampled within each main plot by the releve method for species composition and cover and tree seedlings were counted individually. The plots were subsequently marked with GPS coordinates and resampled at roughly 5-year intervals.
Results/Conclusions
Initially the entire bald were dominated by the mountain oat grass (Danthonia compressa) along with areas of Vaccinium and Rubus canadensis. There was a gradual but steady reduction of grass cover and increase of shrubby cover until the present condition where the bald is almost entirely tree or shrub cover. Presently there is <5% grass cover with thick Rubus and Vaccinium cover over most of the bald. All 4 of the plots are now located under a closed spruce-fir forest of approximately 30-35 year old trees. Forest encroachment has moved primarily downward from the upper margins of the bald and along washed out areas but there are now numerous tree saplings scattered over the entire bald. These plots showed more rapid succession than might have been expected from the earlier literature, where the grassy state was considered relatively stable. It is possible that the thick grassy vegetation does retard invasion for extended years and that the presence of grazing and fires also contribute to bald maintenance. However once shrub and tree seedlings are allowed to establish, succession seres proceed at rates comparable to other forests. Barring further disturbance, the bald is likely to disappear before the end of this century.