Decomposition of aspen, spruce, and pine boles on two sites in Minnesota

Boles of quaking aspen Populus tremuloides, white spruce Picea glauca, red pine Pinus resinosa and jack pine Pinus banksiana were sampled after decomposing for 11-17 yr. Density decreased 40-73%, and the decomposition constant (k) decreased in the order aspen > spruce > red pine > jack pine. Although the decomposition rate was strongly species-dependent, it did not differ between sites. The decomposition constant was weakly related to lignin and P concentration in the original stems, and not significantly related to original N concentrations. Nutrient concentration increased during decomposition, particularly for N and P. Nitrogen content increased during decomposition, and K content decreased. Phosphorus content increased or decreased, depending on species. In general, species with the lowest initial nutrient contents had the greatest nutrient increases during decomposition. -from Authors