Properties of soils representative of the elevation from 4,500 to 6,600 feet in the Smokies along the North Carolina-Tennessee border are reported.
Mean annual rainfall exceeds 80 inches. Mean air temperatures are: annual 45° to 49°F.; January, 31° to 35°F., July, 59° to 63°F. Parent rock is feldspathic sandstone and conglomerate. These soils can be placed in two groups: (1) lacking A2 horizons with thin A1 and “color B” horizons, and (2) with A2 horizons, Bir horizons, and relatively thick mor layers. Soils of the first group ordinarily occupy well-drained sites under spruce-fir forest. Those of the second group occupy less well-drained sites under heath bald or rhododendron understory of sprucefir, with some indication that they tend to form from more quartzose conglomeratic rock.
Soils of the first group are ascribed to the Sol Brun Acide great soil group on the basis of very low base status and high exchangeable Al, C/N levels, lack of relative accumulation of free iron and of layer silicates, and lack of A2 horizons. Second group soils are excluded from the Sol Brun Acide group, due to the presence of A2 horizons, differential iron accumulation, and C/N levels, and are interpreted as Podzols.
Possible mechanisms are proposed to account for contrasting properties of the Sol Brun Acide and Podzol soils described, and the anomalous absence of A2 in the Sol Brun Acide of the Smokies. Extreme acid hydrolysis, producing intergradational three-layer silicates plus kaolinite and gibbsite weathering end products, is postulated for these soils.