Moisture Depletion by Forest Cover on a Seasonally Saturated Ozark Ridge Soil
1957
Many broad, flat-topped ridges in the Ozark Province of Missouri have a subsoil pan horizon at 2 to 4 feet beneath the soil surface. This pan limits the depth of root penetration and restricts water movement to deeper depths. Winter excesses of precipitation are held in and above the pan as a “perched” water table. Records from shallow wells showed that free water occurred within 3½ feet of the soil surface throughout most of the winter months, persisting almost continuously from November, 1954, to August, 1955, where the trees had been cut, and from December, 1954, to June, 1955, in the adjacent undisturbed forest. A dense stand of oak trees, 4 to 8 inches in diameter, having roots in this saturated zone, caused a pronounced diurnal fluctuation in the rate of recession of the water level during April and May. Estimates from this record, together with soil moisture records, indicated that evapotranspiration for this forest stand was 0.175 inches of water daily during rainless periods in April and May.
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