Biomass retention following whole-tree, energy wood harvests in central Maine: Adherence to five state guidelines
The expansion of the bioenergy industry in Maine has led to an increase in integrated roundwood and energy wood whole-tree harvesting. A better understanding of the amounts of logging residue left unrecovered on whole-tree harvested sites will enable the refinement of available forest residue estimates for Maine and the assessment of the potential effect of such harvesting on forest health. Several states have developed biomass harvesting guidelines in response to concerns generated from an expanding bioenergy industry. In this study downed wood and snags were inventoried on twelve sites in central Maine that had recently been whole-tree harvested for roundwood and energy wood. The percentage of harvested material retained as residue on the study sites was determined. On average, 45% of the energy wood generated during the harvest was left on site. This removal efficiency must be considered when developing forest residue availability estimates. Additionally, the volumes of logging residue were compared to measurable criteria from biomass and biodiversity guidelines of several states. We found that enough fine woody material (<15 cm diameter) remained on the harvest sites to meet the guideline criteria; however, the quantities of coarse woody material (≥15 cm diameter), large logs (≥38 cm dbh), and snags (≥25 cm dbh) were insufficient to meet the guideline criteria. These deficiencies likely resulted from prior forest practices rather than from the current energy wood removal. Retaining more trees of larger sizes in the future can address this concern.