Moisture Regimes and Morphological Characteristics in a Hydrosequence in Central Massachusetts
1984
Pickering, E. W. | Veneman, P. L. M.
Moisture regimes and associated soil mottling patterns were investigated over a 2-y period in a Paxton-Rainbow-Ridgebury-Scarboro hydrosequence in central Massachusetts. Changes in physical conditions in these coarse-loamy fragipan soils were monitored with well points, tensiometers, soil temperature probes, and redox potential electrodes. Well-drained soils appeared uniformly brown, reflective of a generally strongly oxidized environment. They also showed the greatest seasonal fluctuations in soil temperature ranging from 0 to 23°C. Matrix colors of highest chromas (6 or higher) occurred in the moderately well-drained (MWD) soils where reducing and oxidizing environments coexist within the profile at some time during the growing season. Prominent ferrans and albans in the 2Cx horizons of MWD soils were related to sustained groundwater levels, although higher water tables often occurred for periods too short or too cold for development of strongly reducing conditions. The characteristics grey streaking patterns of fragipans were best expressed in the 2Cx horizons of MWD soils and can be attributed to reducing environments during periods with soil temperature above biologic zero when conditions are wet but unsaturated. Significant translocation and leaching of iron occurred in the somewhat poorly drained soils, as evidenced by olive-grey matrix colors. Channel neoferrans and some neoalbans indicated that a reducing environment may persist within the B2 horizon long after it has become unsaturated. Lowest chroma colors in this hydrosequence was found in the very poorly drained soils where perennial conditions of saturation or near saturation exists up to the soil surface resulting in the strongest reducing environment and least fluctuations in seasonal temperatures.
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