Woody biomass harvesting guidance

Michigan has developed a guidance document to help forest owners, harvest contractors and others to better understand where caution should be taken in harvesting woody biomass for energy.

Michigan has developed a document called “ Michigan Woody Biomass Harvesting Guidance.” It’s a concise 18 page outline that, when followed, should reduce environmental risks associated with energy harvests. The guidance was developed by a team of experts from industry, universities, non-government groups and key public agencies. It is available on the Michigan Department of Natural Resources (DNR) website.

Might harvesting biomass for energy purposes decimate our forest lands? This is a good question and the answer is resoundingly – not likely at all.

Forest owners are the folks that decide when, and if, any sort of timber harvest will occur on their property. Adding a new market, such as wood energy, to the mix of choices will not lead to a long line of forest owners wanting to harvest timber. Data from research done in Wisconsin and Pennsylvania support this intuitive premise.

However, having a market for low quality wood provides a much needed opportunity across most of the region.

The stumpage and mill prices for energy biomass are low. Typically, this sort of harvest operation needs to be done in concert with other product removals, such as pulpwood and sawlogs. Otherwise, the money isn’t always there for either the forest owner or the logger.

So, right off the bat, irresistible incentives to “decimate” forest lands don’t exist.

Nevertheless, woody biomass for energy is regularly harvested from many timber sale operations. Sometimes, the questions arise about nutrient impacts to the soil or the quality of wildlife habitat. These are more good questions that have pretty solid answers.

Nutrient impacts of timber harvest have been studied for decades. There are, indeed, certain forest types on certain sites where caution will be prudent. However, by and large, biomass harvest on most of our northern forest types, on most of our soils, does not present any issues with long-term nutrient loss.

As far as habitat goes, much will vary with the wildlife species in question. Generally, it is a good idea to leave, or create, such characteristics as standing snags, large logs on the ground, a shrub-sapling layer and other structural features that make up a diverse set of habitat conditions.

Energy harvests won’t change these prescriptions.

The Woody Biomass Harvesting Guidance is designed to be used in concert with the Sustainable Soil and Water Quality Practices on Forest Land manual (from the DNR), which describes practices for a range of resource protection. The guide is also compatible with forest certification requirements.

The guide advises biomass retention of a sixth to a third of the residues from timber harvest spread across the harvest site. If the site has little woody debris to begin with or if the site is particularly nutrient-poor, then leaving more biomass on the ground is recommended.

Biomass harvesting should be avoided in certain special conservation areas, unless the removal may enhance the management objectives. Leaf layers, stumps and roots should be left. Large woody pieces should be left. Some of the standing dead trees and cull trees should be retained, when possible.

The guide cites additional recommendations for several specific situations, such as riparian zones, storm-damaged sites, exotic species and others.

The Michigan Woody Biomass Harvesting Guidance is part of a package designed to help ensure the protection of forest resources. Other states, such as Minnesota, Wisconsin and Pennsylvania have similar guidelines.

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