Biomass Harvesting Guidelines affect downed woody debris retention

Our objective was to determine if a retention area-based Biomass Harvesting Guideline (BHG) strategy maintained desired volumes of downed woody debris (DWD) following woody biomass harvests. We implemented six randomly-assigned treatments in four clearcuts in loblolly pine plantations in the Coastal Plain physiographic region of North Carolina during 2010-2011: 1) woody biomass harvest with no BHGs (NOBHG); 2) 15% retention with woody biomass dispersed (15DISP); 3) 15% retention with woody debris clustered (15CLUS); 4) 30% retention with woody biomass dispersed (30DISP); 5) 30% retention with woody biomass clustered (30CLUS); and 6) no woody biomass harvest (i.e., clearcut only; NOBIOHARV). Prior to harvesting, we flagged 15% or 30% of the treatment area to serve as woody biomass retention sources for the four BHG treatments, and all woody biomass from the flagged area were retained and distributed across that entire treatment area. We examined effects of treatments on: 1) fraction estimated volume of pre-harvest standing volume (total and woody biomass) retained as residual DWD; and 2) fraction retained DWD in treatments 2-5 relative to retained DWD in the NOBHGS and NOBIOHARV treatments. Adding a woody biomass harvest reduced volume of residual DWD by 81% in NOBHG compared to NOBIOHARV. Estimates based on the second metric were most similar to target retentions with retention percentages at 18.8% in 15CLUS, 14.1% in 15DISP, 39.0% in 30CLUS, and 38.0% in 30DISP. Treatments resulted in retention of DWD fractions approximate to those prescribed, suggesting BHGs can be implemented successfully in an operational setting.