Anomalies and Sampling Variation in Forest Soil Water Measurement by the Neutron Method
1972
Sartz, Richard S.
Sampling errors were determined for neutron meter measurements of soil water content in a heterogeneous forest soil. Water content variance at individual 30-cm depths on uncut plots increased with depth at a high water content but was uniform at a low water content. The variation was greater at a low than at a high water content on uncut plots, but was about equal on cut plots. Water content changes over a period of time were more variable than water content at a single point in time. Coefficients of variation for individual depths ranged up to 76% for uncut plots and up to 137% for cut plots. Coefficients of variation for total profile storage were a little lower for change in water content than for total water content on uncut plots, but the relationship was reversed on cut plots. Soil depth differences contributed substantially to the variance of total storage changes, but variable soil depth must be considered in sampling schemes designed to determine total water use under different cover conditions.
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