Hydrological components of a young loblolly pine plantation on a sandy soil with estimates of water use and loss

Fertilizer and irrigation treatments were applied in a 7‐ to 10‐year‐old loblolly pine (Pinus taeda L.) plantation on a sandy soil near Laurinburg, North Carolina. Rainfall, throughfall, stemflow, and soil water content were measured throughout the study period. Monthly interception losses ranged from 4 to 15% of rainfall. Stemflow ranged from 0.2 to 6.5% of rainfall. Rainfall, leaf area index (LAI), basal area (BA), and the interactions of rainfall with LAI or BA influenced prediction models of throughfall, but not stemflow, on a stand level. We found significant differences due to the effects of treatments in the soil water of the top 0.5‐ and 1‐m soil layers by the beginning of the second growing season and throughout the remainder of the study period. Average daily water use and loss from a 1‐m soil layer reflected the low water‐holding capacity of the sand. Soil water in a 1‐m layer was rapidly depleted to within 10% of available water during periods of little or no rainfall. Irrigation did not significantly affect productivity and created a greater potential for loss of water to drainage below 1 m. On the basis of Zahner's [1966] method of soil water depletion in a sandy soil under forest cover, total drainage to below l m was 55% of evapotranspiration in unirrigated plots and 150% of evapotranspiration in irrigated plots.