Weight loss and nutrient changes in decomposing litter and forest floor material in New Brunswick forest stands

Weight loss and nutrient (N, P, K, Ca, Mg) changes with decomposition were examined over a 2-year period fora variety of kinds of litter on five forest sites. Litter types included pine needles, leaves of four deciduous species (red maple, pin cherry, trembling aspen, and white birch), branches of pine and four deciduous species, understory vegetation, and partially decomposed forest floor material, while the study sites consisted of jack pine stands aged 16, 29, and 57 years and mixed hardwood stands aged 7 and 29 years. Statistically significant differences in rate of weight loss were found to occur, with understory and leaf litter significantly faster on the hardwood stands than on the pine stands, understory litter faster on the 7-year-old hardwood stand than on the 29-year-old stand, and forest floor material faster on the 29-year-old pine stand than on the 57-year-old pine stand. Among the four deciduous species examined, significant differences in leaf weight loss also occurred, but differences among branch litter were nonsignificant. The mass of N in samples generally decreased with decomposition, with increases occurring in a few cases (i.e., pine understory and needle litter). Phosphorus mass generally increased on the pine sites and decreased on the hardwood sites; this appeared to be largely a function of the low initial P concentrations of litter on the pine sites. In general, the mass of K, Ca, and Mg decreased in the various samples with decomposition; the loss of K from deciduous leaves in this study was particularly fast and was greater than other values from the literature.