Soil Moisture under a Young Loblolly Pine Plantation
1953
Hoover, Marvin D. | Olson, David F. | Greene, Geoffrey E.
The study reported was made near Union, S.C., to determine the moisture available for tree growth and the effectiveness of young pines as a protective cover on watershed lands. Fibreglas electrodes were used to obtain daily estimates of soil moisture. Rain falling through the tree crowns or flowing down the stems was collected by catchment devices. The amount of rainfall reaching the soil and available soil moisture to a depth of 66- inches for the period October 1950 through September 1952 is reported for a loblolly pine plantation established in 1941. An average of 86% of rainfall as measured in the open reached the ground under the pines. About one-fifth of the rain received under the trees reached the ground by flowing down the tree trunks. During the dry winter of 1950–51, rainfall was insufficient to replenish soil moisture at depths below 30 inches, and trees were almost completely dependent upon rainfall of the 1951 growing season. Rainfall during the winter of 1951–52 brought the upper 66- inches of soil to field capacity providing almost 10 inches of available water for tree growth. Early in the growing season, moisture was lost throughout the entire soil depth studied. Water was withdrawn most rapidly from the zone where it was most readily available regardless of depth, despite the greater concentration of roots in the surface layer. Because of the large draft upon soil moisture throughout the zone the upper 5½ feet of soil under trees has a large capacity to store water from fall and winter rainfall.
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