Effects of Woody Biomass Retention On Soil Quality in Lower Coastal Plain Soils of North Carolina.

The harvest of small stems and woody residuals for bioenergy can increase trafficking and nutrient removal above traditional forest harvest operations and negatively impact soil quality.  This study of biomass removal investigated the effects of different levels of biomass retention on surface soil bulk density, C and N concentration during harvest of a Pinus taeda (L) plantation in the North Carolina Coastal Plain.  Each of four large (> 100 acres) harvest blocks were divided into plots that were randomly assigned one of six biomass retention treatments: all harvestable biomass removed, 30% of harvestable biomass retained evenly distributed on the site, 30% of harvestable biomass retained distributed in piles, 15% of harvestable biomass retained evenly distributed on the site, 15% of harvestable biomass retained distributed in piles, and traditional clear-cut harvest without residue harvest. Differences between pre- and post-harvest soil bulk density and residue nutrient concentrations and contents occurred, but no differences occurred among biomass retention treatments. Analyses of soils adjacent to woody debris piles indicated little impact on soil conditions beyond 1 m.  We conclude that the additional removal of woody biomass for energy following traditional forest harvest has minor impacts on soil conditions.