Soil‐Landscape Relationships of a Climax Forest in the Allegheny High Plateau, Pennsylvania

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Abstract
The Tionesta Research Natural Area, located in the Allegheny National Forest of northwestern Pennsylvania, is a unique remnant of the old growth American beech (Fagus grandifolia L.)‐Eastern hemlock (Tsuga canadensis L.) forest that once covered over 2400 ha of the Allegheny Plateau. During a detailed soil survey, the soils occurring on the various landscapes in the area were characterized and the relationships between the vegetation and the soils were evaluated. The development of the landscapes in the Tionesta area has been strongly influenced by the contrasting erodibility of alternating layers of sandstone, siltstone, and shale bedrock. The gentle, regional dip of the bedrock in a southwesterly direction has favored the preferential erosion of the south‐facing slopes. The area experienced a periglacial climate during the Late Wisconsin Glaciation. Evidence of this former cold climate is expressed by colluvial (solifluction) deposits and boulder fields on the ground surfaces of the footslope landscapes. Seven distinct soils occur on the various landscapes. These soils are extremely acid to very strongly acid and high in exchangeable aluminum. Low cation exchange capacity and base saturation reflect the abundance of quartz and other primary minerals which are highly resistant to weathering. Podzolization processes are evident and most pronounced in the coarse‐textured, free‐leaching soils under hemlock stands. Drainage appears to be an overriding soil factor influencing the vegetation patterns on the different landscapes with hemlock dominating the stands in wetter areas. Shade‐intolerant species, such as black cherry (Prunus serotina L.), commonly occur on shallow soils on steep slopes where frequent canopy openings associated with blow‐downs have allowed their establishment.

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