Mountain knobs protrude above the cool, damp forests of red spruce and Fraser fir in the Southern Appalachians. Alder bushes are the most tree-like species that naturally encroach on these sites. The occurrence of the balds has been attributed to Indian ceremonial burial grounds—which, over long periods of time, would have altered the vegetation. In this cold clime and high altitude, plant life recovers slowly (see Chapter 1).
Ecologists, however, variously believe this phenomenon to be due to overbrowsing by wildlife or livestock, to intense fire at the summit, to ice storms, to exposure to high winds, to a toxic substance in the soil, and to inadequate nutritional elements for sustaining tree growth. To some, post-glacial climatic fluctuations are convincing as a cause. The occurrence of the balds is not a matter of a high-altitude temperature-dependent tree line, as in the West or Far North, for no such demarcation occurs in the Appalachian Mountains. A neophyte observer may suggest shallow soils at the tops of these geologically old and eroded hills, only to learn with the aid of a spade that the mantle covering the rock is often more than 5 feet deep. In spite of this favorable soil depth, the treeless, well-drained sites probably never supported stands of trees.
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