Biomass Thinning in Jack Pine

 

1. Name - Biomass Thinning in Jack Pine

Context | Objectives | Treatment Specifics | Utilization | Targets | Pre Treatment Data | Post Treatment Data | Links

The Nature Conservancy (TNC) manages land to protect ecosystems and imperiled species. In the Paul Bunyan Savanna (PBS), the dune deposits and accompanying vegetation community are unique in the area. Unlike other sites around Minnesota, the dune landforms and relatively poor soil conditions at the PBS appear to have limited the spread of jack pine and restricted the development of a shrub layer underneath the jack pine. This has restricted the development of a forest and maintained a more open habitat, allowing light to reach the ground and enabling prairie plants to coexist with the jack pine. The persistence of this transitional habitat has also been influenced by the presence of fire on the landscape during pre-contact times. Fire returned to this region about every twenty years, each time burning the ground vegetation, shrubs, and some of the jack pine. The dune landforms exerted an influence upon the behavior of these fires, with dune crests and swales burning irregularly due in part to differences in slope, exposure, and vegetation cover. This contributed to a patchy and unique jack pine habitat.

Before and after treatment 

The advent of fire suppression removed a major shaping force on the landscape, changing the appearance and function of the Paul Bunyan Savanna. Although still constrained by soils and dune landscapes, jack pine were no longer subject to regular disturbance by fire. As the jack pine responded by increasing in density, they reduced the amount of light reaching the ground and impacted the growth and development of the prairie plants beneath them. Selective thinning of jack pine was implemented to recreate the patchy habitat that would have been in place had the return of fire to the site been uninterrupted. Restoration was completed during 2005 when fire was reintroduced to the PBS.

TNC thinned approximately 45 acres of jack pine to achieve densities associated with a jack pine savanna habitat. The prescription called for removing all but 20 marked jack pine trees per acre and reserving all aspen, bur oak, red oak, and pin oak. The sale generated about 545 cords (about 12 cords per acre or about 32 tons per acre) at an appraised value of $29 per cord. The contractor, which TNC had some difficulty securing, sent approximately 40% of the cut to a stud plant and the rest went for pulp. The jack pine were stand grown, so even going down to a 4 inch taper on the top, there was excessive slash on the site. TNC had requested whole tree skidding to reduce impacts and to consolidate the slash since the plan was to employ prescribed fire on the site. Another contractor then came in and ground the slash for use as biofuel about 30 miles away in a local ethanol plant. It was used for heat during ethanol production, not to produce the ethanol.

In our case, only the residuals from the harvest went to biomass utilization. If it had not been for the component of prescribed fire, we would likely have required the slash to be broadcast throughout the site and reduced to a foot or less from ground level. The biomass contractor was given the slash at no cost. Since this harvest, the contractor has begun charging for removing slash from sites due to unanticipated costs of doing this type of work.

Links
TNC's Paul Bunyan Savanna
Site Photos by Eli Sagor
Timber Sale Notice