EFFECTS OF SOIL COMPACTION AND CHIPPED ASPEN RESIDUE ON ASPEN REGENERATION AND SOIL NUTRIENTS

The effects of soil compaction and depth of chipped aspen residue on a spen regeneration, plant community development, decomposition, and nut rient cycling were tested on an Orthic Gray Luvisol in the Lower Footh ills of Alberta. Twenty-seven 100-m x 15-m plots were established in 1 992. Three depths of chipped aspen residue (0, 1-5 cm and >10 cm) and three levels of compaction (no compaction, 6 and 16 skidder passes) we re applied following whole-tree harvesting in 1993. Sixteen skidder pa sses and chip residue depths >10 cm resulted in reduced plant cover an d aspen sucker densities for at least 2 yr following treatment. Nutrie nt concentrations of the chip residue and surface organic horizon (LFH ) were similar for the three compaction treatments. The initial total nitrogen (N) concentration of the chipped aspen residue was 3.6 g kg(- 1). Ammonium (NH4+-N) concentrations in the LFH of the chip residue tr eatments, particularly at the >10-cm residue depth, were lower compare d with the no-residue treatment. However, adequate N apparently was av ailable to the aspen suckers and understory vegetation as the NH4+-N c oncentration remained higher than in the LFH before harvesting. Compac tion and woody residue applications had only short-term (3 yr) effects on soil properties, plant community development and aspen suckering a t this site when clear-cut harvesting was done in the fall with low so il moisture content.