Effect of Tree Spacing and Understory Vegetation on Water Use in a Pumice Soil1
- James W. Barrett and
- C. T. Youngberg2
Water use in a pumice soil in central Oregon increased significantly with increased density of a sapling ponderosa pine (Pinus ponderosa Laws.) stand.
Study plots were thinned to 62, 125, 250, 500, and 1,000 trees/acre and replicated six times. Soil moisture measurements were begun 2 years after thinning and continued for three successive growing seasons. Soil moisture was measured with a neutron probe at three permanent stations on each plot at 3-week intervals during the summer.
Total amount of water use was 1.6 times greater on plots containing 1,000 trees/acre than on plots containing 62 trees/acre. Moisture use on plots where understory vegetation was allowed to develop normally was 45% greater than on plots where vegetation was removed. Soil in the area is a Regosol developed in dacite pumice, approximately 7,300 years old, from the eruption of Mount Mazama (Crater Lake).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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