Root zone physical and chemical characteristics in southeastern spruce-fir stands

Because of their remote location and relatively limited extent, soils, in the southeastern spruce-fir zone have not been extensively characterized either physically or chemically. The objective of this study was to describe and characterize the soils found in most of the major spruce-fir areas in the Southeast as a first step in evaluating potential growth changes in the region. Fifty-two soil profiles, randomly distributed within the spruce-fir cover type, were described and samples were collected for physical and chemical analysis. Soils sampled were classified into the following taxonomic subgroups: Lithic Borofolists, Umbric Dystrochrepts, Lithic Haplumbrepts, Typic Haplumbrepts, Pachic Haplumbrepts, and Lithic Haplorthods. The data set was further condensed by focusing only on the rooting zone as defined for each pit by field measurements. Mean rooting depths ranged from 17 to 39 cm. All profiles were strongly to extremely acid (pH 3.6-4.6), with CECs in the 28 to 39 cmol kg-1 range and base saturation less than 4%. Considerable variability was seen among soils in organic matter (132-312 g kg-1) and total Kjeldahl N (TKN) content (5.4-11.0 g Kg-). Statistically significant (P = 0.05) differences also occurred in exchangeable base cations, while total cations exhibited less variability among groups. Extractable P varied little among these subgroups with only the Pachic Haplumbrepts having significantly higher concentrations. Total P exhibited more variability in concentration. Acetate-soluble SO4-S ranged in concentration from 0.08 to 0.67 g kg-1. Extractable and exchangeable A1 concentrations were generally lowest in the Lithic Borofolists and highest in the Lithic Haplumbrepts. Observed variations are attributed primarily to differences in organic matter accumulation and to the impact of soil creep/soil mixing due to general slope instability.