NEW RESEARCH ON HEATH BALDS IN GREAT SMOKY MOUNTAINS NATIONAL PARK: SURPRISING RESULTS FOR RESOURCE MANAGEMENT AND FOR SCIENCE

A detailed investigation into the soils of the heath balds in Great Smoky Mountains National Park (GSMNP) sheds new light on the origin of the balds in addition to providing valuable data for resource management. Of perhaps greater importance, this study also uncovered a previously undescribed reservoir of paleoclimate data for the southern Appalachians. Soil pits were dug to bedrock in balds at 14 sites widely distributed throughout GSMNP. Pits were sampled for radiocarbon dating, soil chemistry, macrofossils, and pollen. Analysis indicates that the bald soils have unique properties that help explain the origin and evolution of heath balds on the landscape. The soils are highly organic (80-95% LOI) all the way to bedrock (depth up to 1 m). They are extremely acidic, with pH below 3, and have a very low base saturation. Aluminum saturation is very high giving the soils a low productivity rating. Many sites had a substantial basal charcoal layer. Radiocarbon (AMS) data indicate a minimum age of formation for the balds sampled ranging from 3000 to 100 years BP with a tenuous clustering of ages at 2900, 1700, 1100 and 120 years BP. We have developed the following model for the evolution of heath balds on the southern Appalachian landscape. Heath balds are initiated by forest disturbance, most likely fire, removing the canopy and allowing the rhododendron in the understory to dominate. Once established, the rhododendron thicket is self-sustaining through the development of the extreme soil conditions described above. Organic matter accumulates due to reduced microbial activity in the low productivity soils. Climatic conditions prevent substantial fire at the higher elevations of GSMNP today, therefore, it is suggested that balds have formed primarily during periods of dryer climate (hence the proposed clustering of ages). It is also apparent that certain balds may be naturally expanding as the bald soils “poison” the forest edge. This creates a fringing forest extremely vulnerable to invasion by pests and exotics. Finally, significant accumulations of pollen were found with what appears to be good stratigraphy. The 300+ balds in GSMNP could provide the most important data set for Holocene paleoclimate in the southern Appalachians.