Woody Biomass Retention Guidelines

Considerations and Recommendations for Retaining Woody Biomass on Timber Harvest Sites in Maine

There is intense competition for raw material within Maine’s forest products industry. In addition to traditional round wood markets, bioenergy facilities that produce electricity by burning wood are common throughout the state. Some are stand-alone facilities and others are integrated within pulp and paper mills. Biomass chip harvests in Maine have increased more than 3½ times since 2000 (Figure 1) – a trend that is expected to continue given plans for new and expanded capacity in the region. Several wood pellet plants are either in operation or planned for construction. Industry analysts expect global production of wood pellets for residential and commercial heating to increase 25 to 30% annually over the next decade. Research is also in progress at the University of Maine to produce a variety of forest bioproducts including ethanol.

Historic biomass chip harvest levels in Maine (Maine Forest Service 2008).

Figure 1. Historic biomass chip harvest levels in Maine (Maine Forest Service 2008).

We do not know the impact these new initiatives will have on wood supply, but it is certainly possible that competition for raw material between wood-using facilities will increase. Increased competition may impact harvest levels through shorter rotations, or increased use of small diameter and poor quality stems. This may create opportunities for timber stand improvement by combining such harvests with conventional forest management and silvicultural treatments. Regardless of the outcome, there is concern that these and other related activities will put more pressure on our forests. Wood supply is a concern for both traditional wood processing sectors and the emerging bioindustry, and the general public has raised concerns regarding long-term sustainability of biomass harvesting.

Increased demand for woody biomass will generally increase the potential for conflicts among forest values. For example, a standing dead tree may provide habitat for wildlife, reduce soil compaction and erosion if used in skid trails, or provide economic value to a bioenergy facility. Logging residue can be used to maintain soil productivity, reduce erosion, or produce bioproducts. All values cannot be achieved in each case, so tradeoffs may be necessary. The forest industry in Maine has been dealing with these and other related issues for many years, but guidelines specific to woody biomass retention are missing from existing best management practices and regulations.

This report and associated guidelines focus on the amount and type of woody biomass that should be retained in the forest after a harvest operation to protect soil productivity, water quality, and site-level biodiversity. Woody biomass, defined from a forest operations perspective, is comprised of logging residues, previously unmerchantable stems, and other such woody material harvested directly from the forest typically for the purposes of energy production. In the broadest sense woody biomass is the total mass of roots, stem, branches, bark and leaves of all tree and shrub species (live and dead) in the forest. Under the broad definition all forest products could be considered as woody biomass, but in practice a forest operations perspective is more appropriate for this initiative. Harvest of woody biomass is often integrated with traditional forest operations, so it can be difficult to isolate effects of woody biomass removals at a site level. As such, it is important to consider retention of woody biomass during all harvest activities and to emphasize post-harvest site condition rather than the amount of any given product removed during harvest. The objective of this report is to recommend guidelines for retention of woody biomass on harvest sites from a general perspective (Section 3) and with respect to soil productivity (Section 4), water quality (Section 5), and site-level biodiversity (Section 6). Background information is provided on each topic based on a review of relevant scientific literature and harvesting guidelines from other states with similar forest types and markets.

Site specific guidelines are primarily based on a number of published documents, including:

Best Management Practices for Forestry (Maine Forest Service 2004)
Site Classification Field Guide (Briggs 1994)
Biodiversity in the Forests of Maine: Guidelines for Land Management (Elliott 2008).

Production of these guidelines was a collaborative effort between the Maine Forest Service, the University of Maine, and the Trust to Conserve Northeast Forestlands. This effort was supported by funding from the Natural Resources Conservation Service, Maine Forest Service, the University of Maine’s Forest Bioproducts Research Initiative (NSF Grant No. EPS-0554545), and the Maine Outdoor Heritage Fund.

Brochure (pdf format)

Full report (pdf format)

For hard copy of the brochure, please send an email to forestinfo@maine.gov. Hard copies of the full report are not available at this time.