Red pine growth and chemical composition of foliage and forest floors across a precipitation-chemistry gradient in Wisconsin

Three red pine plantations were located at each of five sites across the precipitation-chemistry gradient in Wisconsin (loadings of H ion, SO₄ ^2-, and NO₃ ^- generally decrease from southeast to northwest). The large within-site variation may have masked any differences attributable to variations in precipitation chemistry across the gradient. Site-related differences in radial increment (1982-1986 period) were attributed to time since thinning. There were significant site-related differences in mass, concentrations, and contents (mg/50 fascicles) of N, P, Ca, and S in current needles and in mass, concentrations, and contents (kg.ha^-1) of N, P, and S in the forest floor. Differences in mass and chemical composition and needles among sites may be due to slight differences in soils. The differences in mass and chemical composition of the forest floor among sites were attributed to differences in preplanting site conditions and stand treatment. -from Authors