Nutrient content of throughfall and stemflow in fertilized and irrigatedPinus resinosa ait. Stands

Summary The P, K, Ca, and Mg contents of throughfall and stemflow from K-fertilized and/or irrigated plots from adjacent sites differing in productivity in 39-year-oldPinus resinosa plantations were determined. The amounts of these elements leached from the tree canopies (throughfall plus stemflow) during April through October varied significantly according to site and treatment. These amounts ranged in kg per ha from −0.03 to 0.23 for P, 2.05 to 8.78 for K, 1.55 to 3.63 for Ca, and 0.02 to 0.44 for Mg. Leaching of P, K, and Ca from the trees was usually greater on the more productive site than on the poorer one. In general, the fertilization treatment was correlated with increasing amounts of P, K, and Ca leached, whereas the irrigation treatment was correlated with decreasing amounts of P, K, and Ca leached. For Mg, leaching was consistently greater on the poorer site than on the more productive one; further, it was greatest on the control plots and least on plots both fertilized and irrigated. Gross precipitation of 61.26 cm contained P, K, Ca, and Mg in amounts of 0.33, 0.84, 2.96, and 0.83 kg per ha, respectively. Volumes of both throughfall and stemflow were significantly affected by site conditions. Although throughfall was not affected by treatment, stemflow varied significantly according to plot treatment and was also highly and positively correlated with tree diameter. Stemflow accounted for about 2 per cent of the total water volume collected beneath the canopies, and contained, on a relative basis, considerably less P, an equivalent amount of K, twice as much Mg, and four times as much Ca as throughfall. Contribution of the Northeastern Forest Experiment Station, Forest Service, USDA, and Department of Silviculture and Forest Influences, State University of New York College of Environmental Science and Forestry, Syracuse, New York, 13210.