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

Abstract

Three red pine (Pinusresinosa Ait.) plantations were located at each of five sites across the precipitation-chemistry gradient in Wisconsin (loadings of H ion, SO42−, and NO3− generally decrease from southeast to northwest). The plantations were selected to be as similar as possible in stand characteristics, including age, initial stocking, number of thinnings, site index, and basal area, and in soils (mixed frigid Typic Udipsamments or Entic Haplorthods). Despite the care exercised in selecting the plantations, analysis of variance incorporating a nested design showed that for the growth parameters, within-site variation generally was greater than among-site variation. 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 of needles among sites may be due to slight differences in soils. We attribute the differences in mass and chemical composition of the forest floor among sites to differences in preplanting site conditions and stand treatment.