WHY GO BALD? UNDERSTANDING THE AGE AND ORIGIN OF SOUTHERN APPALACHIAN HEATH BALDS IN GREAT SMOKY MOUNTAINS NATIONAL PARK

Some high elevation (4,000 ft – 6,500 ft) areas of the southern Appalachians are characterized by conspicuously treeless zones commonly referred to as balds. These balds can be either “grassy balds” or “heath balds” and are surrounded by otherwise typical forest. Globally, treeless areas are common above a climatically controlled treeline. In the southern Appalachians, none of the mountain tops or ridges are “above treeline.” For the last 100 years, many researchers have pondered the existence of these persistent open areas with a great deal of speculation as to their origin. While studies to date have tended to lump the two bald types together, it is apparent that most workers have focused on the more easily accessible and more visually stunning grassy balds. Theories for their formation have generally fallen into the following categories: 1) Human disturbance-driven, either pre- or post-European; 2) Natural disturbance-driven, either fire or native herbivore grazing; or 3) Climate-driven, possible xerothermic glacial or post-glacial climate. Recent soils mapping in Great Smoky Mountains National Park (GSMNP) has initiated a detailed examination of heath bald soils. The results have been quite intriguing. The heath balds are underlain by a soil best classified as a Folist (dry organic soil) ranging in thickness from just over 1 m to just less than 50 cm. Below, there is a very thin weathered bedrock layer and then solid bedrock (metasedimentary sandstone and slate). These organic soils are extremely acidic, with pH's below 3, and have a very low base saturation. The organic matter has an extremely high Cation Exchange Capacity (CEC). The soils have a low productivity rating. Aluminum saturation is extremely high which lends to the low productivity of these soils. Loss-on-ignition analysis yields values ranging from 80-95% organic matter. These heath bald soils are, by far, the most organic-rich soils in GSMNP. Within the organic horizon there is no apparent change in nature of the soil. Recent radiocarbon data indicate that those soils sampled to date give a basal age of approximately 3,000 yrs. BP. This would certainly rule out a European settlement origin for the heath balds. Data collected thus far suggests that the heath balds may have a multiple-cause origin driven by natural disturbance.