Retention of Soil Water Following Forest Cutting
1977
McColl, J. G.
Eucalyptus globulus (Labill.) forests in the Oakland-Berkeley hills, California, were clearcut in 1973–74 following severe damage from freezing in December 1972. The soil water regimes in clearcut and adjoining uncut areas, were compared during the two years following cutting. During the wet winter season (Dec.–May), surface drying and evapotranspiration by annual grasses were the only losses in the clearcut; more soil water was retained in the clearcut due to lack of evapotranspiration by the forest trees. Soil water rapidly decreased in both the clearcut and forest during the long, dry summer periods, and differences between the two areas widened. By midsummer soil matric suctions in the clearcut dropped below 15 bars (22.4% Pᵥ, volumetric water content), and in the forest to below 70 bars (8.5% Pᵥ). During the summer, Pᵥ increased with profile depth in the clearcut, but in the forest, soil water was depleted uniformly with depth in the profile. Although volumetric water contents of soil (Pᵥ) were significantly different between clearcut and forest areas, rates of water loss (k) during summer were not clearly related to forest cover. In the clay-loam soil, k was dependent on the soil water storage at the beginning of the dry summer period, on the ability of trees in the uncut forest to withdraw water from parent material and from fractured bedrock in excess of that available in the soil profile, and on Pᵥ which decreased during summer.
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