Evaluation of Biomass Harvesting Impacts on Minnesota’s Forests
PROJECT OVERVIEW
Minnesota's forests are currently being viewed as potential feedstocks for the production of renewable energy. A primary concern about harvesting forest biomass to generate renewable energy is the long-term impacts these harvests will have on soil nutrients and long-term ecosystem production, such as forest growth, carbon storage, and wildlife habitat. With this appropriation, scientists at the University of Minnesota's Department of Forest Resources are evaluating the ecological impacts of forest biomass harvesting in northern Minnesota. Results from this effort will be used by the energy industry and forestry professionals in both the public and private sector to guide long-term management that maximizes harvesting without negatively impacting forest productivity and ecological integrity.
OVERALL PROJECT OUTCOME AND RESULTS
Minnesota's forests are currently being viewed as potential feedstocks for production of renewable energy. A primary concern about harvesting forest biomass to generate renewable energy is the long-term impacts these harvests will have on soil nutrients and long-term ecosystem productivity, particularly in forests growing on nutrient poor soils. This project was designed to increase our understanding of the ecological impacts of biomass harvesting through establishment of a network of research sites in forests on nutrient poor soils. Treatments representing various levels of biomass removal and live-tree retention were implemented at four large-scale (80 acre) research sites in Becker, Hubbard, and Wadena Counties and were used to evaluate the importance of post-harvest slash and live-tree retention in maintaining the resilience and sustainability of jack pine forests under different biomass harvesting regimes. Treatments included current site-level guidelines for slash retention to allow for evaluations of the effectiveness of this practice at reducing impacts on long-term soil nutrients and forest vegetation. Field measurements from these sites were used to model the long-term effects of repeated biomass removals on ecosystem productivity. Results from this project indicate that there is no difference in post-harvest slash levels between areas in which slash was retained to meet current site-level guidelines and in places in which whole trees were harvested (i.e., no slash deliberately retained). The overall levels of slash retention in these areas were half those found after similar treatments in aspen-dominated forests on nutrient rich sites, highlighting the potential for greater nutrient depletion following biomass harvesting on nutrient poor sites and suggest a need for refinement of site-level guidelines to increase retention levels for nutrient poor soils. Long-term field data and model results indicate that biomass harvests that retain less than 40% of available residues may result in lower soil carbon stocks after several harvest rotations.
PROJECT RESULTS USE AND DISSEMINATION<
The results of this project have been shared on numerous occasions with resource professionals, policy makers, citizens, and scientists over the past three years in efforts to inform forest conservation decisions regarding biomass harvesting impacts. These dissemination activities have included the development of a fact sheet for LCCMR members that was distributed on the LCCMR tour of Itasca State Park on July 18, 2013. In addition, an overview of the project and results were shared with private forest landowners through a University of Minnesota Extension Webinar to private forest landowners and county, state, and federal natural resource managers on December 9, 2013, as well as through a meeting of the Forest Operations and Planning Section of the Minnesota DNR Division of Forestry on January 8, 2014. Results were also presented at the Annual Meeting of the Ecological Society of America in Minneapolis, MN on August 5, 2013. Finally, results regarding the impact of different levels of post-harvest slash retention on soil nutrients have been discussed with members of the Minnesota Forest Resources Council and are being used to inform future guideline revisions. Publications resulting from this work are available for download from the Department of Forest Resources web site (www.forestry.umn.edu). Additional publications from this work that are currently in development will also be posted on this site and shared with LCCMR staff for dissemination.
$175,000 the first year and $175,000 the second year are from the trust fund to the Board of Regents of the University of Minnesota to assess the impacts biomass harvests for energy have on soil nutrients, native forest vegetation, invasive species spread, and long-term tree productivity within Minnesota's forests. This appropriation is available until June 30, 2014, by which time the project must be completed and final products delivered.
Click on "Final Report" under "Project Details".
Click on "Final Report" under "Project Details".
$175,000 the first year and $175,000 the second year are from the trust fund to the Board of Regents of the University of Minnesota to assess the impacts biomass harvests for energy have on soil nutrients, native forest vegetation, invasive species spread, and long-term tree productivity within Minnesota's forests. This appropriation is available until June 30, 2014, by which time the project must be completed and final products delivered.
Click on "Final Report" under "Project Details".
Click on "Final Report" under "Project Details".