CASE STUDY 2 - An ecological study of the heath balds of the Great Smoky mountains
What is a heath bald?
The inhabitants of the Great Smoky mountains usually refer to the heath communities under consideration "balds." The former name is derived from the smooth appearance they present on the ridges and mountain tops when viewed from a distance and which is entirely misleading, for they are extremely rough and tangled. The name "bald" refers to the absence of trees, these areas being exclusively occupied by shrubs. The term "heath bald" is used to include all such treeless areas dominated. |
Vegetations: content and relation to surrounding forests
Before going into the peculiarities of the heath balds and their relationship to the adjacent forest types, it will be necessary to consider briefly the major aspects of the vegetation of the region as a whole. The vegetation areas of the Great Smoky mountains present some confusion when classifications are attempted, especially on a single basis. The major distinctions should be apparent and consist of climatically controlled vegetational units capable of reproducing themselves and consequently resulting in various dynamic subdivisions related to many factors, yet tending always towards the climax condition of relative stability. This concept of major divisions of vegetation provides for only two formations in the region of the Great Smoky mountains, namely:
Before going into the peculiarities of the heath balds and their relationship to the adjacent forest types, it will be necessary to consider briefly the major aspects of the vegetation of the region as a whole. The vegetation areas of the Great Smoky mountains present some confusion when classifications are attempted, especially on a single basis. The major distinctions should be apparent and consist of climatically controlled vegetational units capable of reproducing themselves and consequently resulting in various dynamic subdivisions related to many factors, yet tending always towards the climax condition of relative stability. This concept of major divisions of vegetation provides for only two formations in the region of the Great Smoky mountains, namely:
- Subalpine Forest: Picea-Abies Formation
- Deciduous Forest: Quercus-Fagus Formation
On the peaks and ridges, shrub species develop an exclusiveness and luxurience that makes them stand out as islands in the surrounding forests. At the same time, however, the heath balds maintain a similarity in physiognomy despite the changing species content. The relation of the bald species to altitude, which is in reality the relation to the contiguous forest type, is brought out as the following:
- 6,500 Feet (Maintop bald) - Rhododendron catawbiense
- 5,000 Feet (Brushy Mountain) - Kalmia latifolia
- 4,000 Feet (Teterhill lead bald) - Sassafras variifolium
Rhododendron catawbiense
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Kalmia latifolia
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Climate, maintenance and distribution
Based on studies, in the region of the heath balds the climate can be briefly described as "oceanic" despite the inland location. Rainfall and relative humidity are high, while the temperature tends to be low, but subject to fluctuations. Evaporation, as measured by the Livingston atmometers, is generally quite low. Rainfall in the higher regions is said to exceed 80 inches a year, a contention well substantiated by a comparison of the' vegetation of the Smoky mountains with regions of high rainfall in North Carolina. In respect to the humidity, it is apparent that the development of heath balds is closely related to upper altitudes almost constantly enveloped by clouds, especially during summer months.
On these factors, fire is by far the most important. The effect of repeated fires can be seen on Brushy mountain. The last three fires have burned successively smaller areas. In the area of the second burn the shrubs are four to five feet high, while nearer the center and top of the mountain, in the zone of the most recent fire, the shrubs are mainly two to three feet high. Some species, as Kalmia latifolia and Rhododendron catawbiense, are particularly resistant to the repeated ravages of fire. Many mountaineers and woodsmen familiar with the region, think that fire is a very important if not universal factor in the initiation and maintenance of heath balds. Despite the frequent importance of fire in eliminating trees from potential heath bald areas, it is not an exclusive factor, especially at higher altitudes, where landslides and windfalls are important contributing factors.
Summary
Heath bald species occur under the protection of lhe contiguous forest, and in more favorable locations (that is, more favorable for the heath bald species) they are so abundant that it seems clear that the elimination of the trees by catastrophic forces would result in establishment of balds, which would effectively, in many instances, prevent reinvasion by the forests.
The problem of the initiation, maintenance and distribution of the heath balds is considered on a basis of climatic, edaphic and catastrophic factors. It is concluded that the heath balds are postclimax, and consequently are derived from the contiguous forest associations as the result of the interaction of a number of factors. The combination and intensity of these factors may be various in the production of different heath balds by the local deterioration or destruction of the forests.
With cool and humid climatic conditions and evergreen vegetation, there is a decided development of edaphic conditions, as high acidity, peat formation and podsolization, which progressively favor heath bald species. In many places it is apparent that the elimination of the trees would permit the under-shrubs to develop a closed cover, which they are apparently quite capable of maintaining, in most instances, against the encroachment of trees.