Leaching of Nitrogen, Phosphorus, and Total Organic Carbon from Loblolly Pine Litter by Simulated Rainfall

Information on nutrients leached from pine litter, which should aid the understanding of nutrient cycling, was derived by applying simulated rainfall to loblolly pine ( Pinus taeda L.) litter in 1.0 m² pans with a multiple-intensity rainfall simulator. In one study, rainfall intensity was varied from 12 to 105 mm · h -1 ; in another study, intensity was held constant at 25 mm · h -1 , but applied to three litter weights of 3.4, 5.3, and 7.8 t · ha -1 . At each intensity and litter weight, 25.4 mm of rainfall was applied. New litter was used for each replicate. Runoff sampled throughout each replicate was analyzed for NH 4 -N, PO 4 -P, and total organic carbon (TOC). Nutrient concentrations in runoff rapidly increased to a maximum and then rapidly decreased to a near constant value in the remaining runoff. Hyperbolic equations, Y = a + b/X , best described the concentration curves as a function of time and runoff volume following the maximum concentration. Regardless of intensity, litter weight, or nutrient, maximum concentration occurred in the first 1.5 mm of rainfall after runoff began; the near constant concentration occurred after the first 14 mm. Nutrient concentrations and losses increased as litter weight was increased; however, in general, neither concentrations nor losses were related to rainfall intensity. Forest Sci. 31:750-759.