Effects of Harvest Season, Soil Texture and Landscape Position On Soil Compaction in Northern Minnesota Aspen Harvests.

In this study we investigated the effects of soil texture, harvest season and landscape position on soil bulk density and surface soil strength for harvests in northern Minnesota. In 2005 we measured recent clearcuts of predominantly aspen stands (Populus grandidentata Michx. and P. tremuloides Michx.) in the Chippewa National Forest. We stratified these clearcuts by the season harvested, soil texture, and by topographic position. In nearly all cases (except for 10-20 cm bulk density in coarse-textured soils) we observed higher bulk density and surface soil strength following harvesting when compared to unharvested controls. Within harvested sites, our data indicate that fine-textured soils had higher surface soil strength (more compaction) than coarse-textured soils, and sites harvested in the summer had higher surface soil strength than those harvested in the winter. Landscape position was only important in fine-textured soils. Both summit and toeslope positions had higher surface soil strength following summer harvesting when compared to winter harvesting. We found no differences in soil bulk density among harvest season, texture or landscape position combinations. Overall, our results indicate that fine-textured soils located on both lower and upper slope positions and harvested during unfrozen soil conditions are most susceptible to compaction during logging.