Minnesota Department of Natural Resources: Split Rock Lighthouse State Park

Paper birch and aspen forests along the North Shore

View of the North Shore from the Park showing stands of conifer dominated forest

Project Area

Dying paper birch and aspen forest at risk of transitioning to grass and shrub cover due to a lack of tree regeneration along Minnesota’s north shore of Lake Superior (image permission of Chel Anderson/ Minnesota Conservation Volunteer).

Many forests along Minnesota’s North Shore are in a degraded condition, with old and dying paper birch and aspen stands that are highly vulnerable to transitioning to brush and grass. Forests along the North Shore were affected by logging followed by severe fires in the early 1900’s, which resulted in the replacement of the conifer-dominated forest with birch and aspen. The more recent combination of increasing stress from extensive deer browsing, warming and drought, and insect pests has limited tree regeneration of the birch and aspen. The Nature Conservancy in Minnesota and the Minnesota Department of Natural Resources are in the planning phase of a project focused on reforesting thousands of acres in the North Shore Highlands of Lake Superior in Northeast Minnesota. Approximately 40 sites totaling more than 2,200 acres located across six State Parks were identified as good having good potential for reforestation. Out of these, a 140-acre parcel of degraded and understocked aspen-birch forest in Split Rock Lighthouse State Park was selected for initial consideration with Adaptation Workbook.

Management Goals

Map of sites considered for reforestation (courtesy of Samuel Reed).

Split Rock Lighthouse State Park is managed by the MN DNR to preserve, perpetuate, and interpret natural features as mandated by state statutes4. Part of this mandate is achieved through restoring desirable species and ecological communities. Given this directive, long-term management goals for the project area include establishing resilient natural communities and providing habitat for rare species and species of greatest concern by promoting an older forest with complex structure and high tree species diversity. The collaboration between TNC and MN DNR focused on planning for reforestation, with the additional benefits of carbon sequestration. These carbon stock gains would greatly increase sequestration on the project area relative to the current condition of the forest that, without intervention, will likely continue to decline from age-related mortality and be replaced by woody shrubs and grass. Two sites were selected totaling 140 acres; site A is a high-use area adjacent to roads, trails, buildings, and a campground, while site B is a natural area not significantly impacted by park visitor use.

Climate Change Impacts

Warming temperatures, particularly in the winters, are expected to intensify existing stressors such as deer herbivory and forest pests and diseases. Deer browse, already a major impact on forest regeneration along the North Shore, may continue to get worse if deer populations rise due to milder winters. Currently deer populations are very concentrated on the North Shore in the winter and spring. Milder winters may also bring intensified disease risk as well. Soil erosion at this site may become a concern as the site is listed as “highly erodible” in the State Park plan and heavy precipitation events continue to become more frequent. More frequent periods of soil moisture stress might increase as a result of warmer conditions, with drier conditions impacting the health of trees growing on the shallow, rocky soils at Spilt Rock Lighthouse State Park. Correspondingly, these soil conditions contribute to the site’s vulnerability to erosion from extreme precipitation events, which are becoming more frequent.

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Declining habitat suitability of paper birch and aspen that currently occupy the site.

Deer browse limiting natural tree regeneration and survival of planting tree stock.

The site is a white pine blister rust hot spot, so planted white pine seedlings would require extra tending and pruning.

Increased stress from more frequent drought and rising temperatures increase the susceptibility of remaining birch trees to the bronze birch borer (Agrilus anxius), an insect pest that increases tree mortality.

Opportunities

Proximity to Lake Superior can buffer summer temperature increases, increasing survivability of seedlings and provide continued habitat for some long-lived conifer species (white cedar, white spruce).

Landscape complexity provides opportunities for diverse microsite conditions for seedlings.

Projected increasing suitable habitat for several temperate tree species.

Adaptation Actions

Project participants used the Adaptation Workbook to develop highlight several adaptation actions with carbon benefits that were included in initial plans for this project, such as reforestation through planting long-lived conifers to increase site stocking, as well as clearing brush to reduce competition. Additionally, using the menu allowed managers to alter some tactics, such diversifying the planting list and modifying the location of conifer planting sites. Depending on the guidelines appropriate for restoring the two sites considered, managers added new tactics, such as using southern genotypes of species currently found in the region, and planting species that occur further to the south (site A only). Adaptation actions include:

Area/Topic

Approach

Tactics