Soil properties, aspen, and white spruce responses 5 years after organic matter removal and compaction treatments

Retaining organic matter and preventing soil compaction are important factors affecting the sustainability of managed forests. To assess how these factors affect short-term ecosystem dynamics, pre-treatment and 1 year and 5 year post-treatment soil properties and post-treatment tree growth responses were examined in a boreal trembling aspen (Populus tremuloides Michx.) dominated ecosystem in northeastern British Columbia, Canada. The experiment used a completely randomized design with three levels of organic matter removal (tree stems only; stems and slash; stems, slash, and forest floor) and three levels of soil compaction (none, intermediate (2-cm impression), heavy (5-cm impression)). Removal of the forest floor initially stimulated aspen regeneration and significantly reduced height growth of aspen and white spruce (Picea glauca (Moench) Voss). The compaction treatments had no effect on aspen regeneration density. At year 5, heights of both aspen and white spruce were negatively correlated (r(2) > 0.31, p < 0.0001) with upper mineral soil bulk density and were lowest on forest floor removal treatments, where minimal recovery from compaction was observed. There was some evidence for recovery of soil properties to preharvest conditions where expansion of herbaceous vegetation increased soil organic matter.