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Evaluation of Relationships Between Oak Site Indices and Properties of Selected Dystrochrepts
Author(s) -
Edmonds W. J.,
Rector D. D.,
Wilson N. O.,
Arnold T. L.
Publication year - 1988
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1988.03615995005200010035x
Subject(s) - cation exchange capacity , feldspar , soil water , saturation (graph theory) , soil series , soil science , mineralogy , chemistry , geology , mathematics , soil classification , combinatorics , paleontology , quartz
Soils derived from argillaceous rocks in the Blue Ridge and Valley and Ridge in Virginia have been mapped and correlated as members of Typic (Berks) and Lithic (Weikert) Dystrochrepts. SCS‐SOI‐5 interpretation records show soils of the Berks series to have higher estimated upland oak site indices than soils of the Weikert series. To explain observed differences in distributions of upland oak site indices, distributions of 34 soil and site properties were evaluated. According to the Shapiro‐Wilk test, the majority of these properties had nonnormal distributions. Therefore, α levels associated with the parametric, two‐sample t ‐test would be unreliable. The nonparametric Wilcoxon rank sum test is distribution free and provides reliable α levels for small samples with nonnormal distributions if the samples have similar dispersions. According to the Moses ranklike test, only available water capacity (AH2O) had significantly different ( p = 0.05) dispersions for Typic and Lithic Dystrochrepts. Typic Dystrochrepts had significantly larger ( p = 0.05) median values for depths to C and R horizons, AH2O, and AL 3+ saturation of the cation exchange capacity (CEC). Lithic Dystrochrepts had significantly larger median values for exchangeable Ca 2+ , total exchangeable bases, CEC, pH‐dependent charge, exchange acidity, ratio of the CEC to clay, and feldspar. Observed median values for upland oak site indices of 56 and 52 for Lithic and Typic Dystrochrepts, respectively, were not significantly different. Significantly larger amounts of feldspar and exchangeable bases, especially Ca 2+ , and significantly lesser amounts of exchangeable Al 3+ saturation of the CEC of Lithic Dystrochrepts are hypothesized as reasons for their slightly higher upland oak site indices. Significantly larger amounts of exchange acidity in Lithic Dystrochrepts are the result of larger amounts of pH‐dependent charge and probably do not adversely influence tree growth. The simultaneous consideration of selected combinations of these properties using discriminant analysis does not produce mutually‐exclusive groups or groups that correspond to limits defined for Lithic and Typic Dystrochrepts. Only the limit of 50 cm depth to bedrock produces classes that correspond to these subgroups.