Recent study tests implementation of biomass harvesting guidelines

Woody biomass harvests have the potential to remove some logging residues and trees that ordinarily would not be merchantable. As a result, guidelines have been developed to minimize potential environmental consequences of woody biomass harvesting.

A recent publication reports results from a study designed to determine if a retention area-based biomass harvesting guideline strategy could maintain desired volumes of downed woody debris (DWD) following woody biomass harvests. The paper was authored by Sarah R. Fritts, Christopher E. Moorman, and Dennis W. Hazel of North Carolina State University, and Ben D. Jackson of the University of Georgia. NCASI and several of its member companies collaborated in the study.

The authors concluded that the retention area-based strategy was successful at retaining target volumes of DWD. They also found that adding a woody biomass harvesting component to a clearcut roundwood harvest decreased DWD relative to sites with a roundwood harvest only, but all treatment units exceeded by at least three-fold the Forest Guild’s recommended minimum volume of DWD to be retained following a woody biomass harvest in the Piedmont and Coastal Plain physiographic regions of the USA.

The abstract for the paper follows.

“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.”

Reference 

Fritts, S. R., C.E. Moorman, D.W. Hazel, and B.D. Jackson. 2014. Biomass harvesting guidelines affect downed woody debris retention. Biomass and Bioenergy 70:382–391. http://dx.doi.org/10.1016/j.biombioe.2014.08.010