Regenerating Hart Lake natural origin red pine using a mix of artificial and natural regeneration (MN DNR)

Overview

This case study will look at the use of both natural and artificial regeneration practices to regenerate a Natural Origin Red Pine (NORP) site in a manner that mimics the structure and diversity of a stand reinitiated by catastrophic fire. Whole tree skidding was used to provide site scarification for natural seeding and planting. Slash raking was used to provide additional scarification where whole tree skidding was limited by terrain or was insufficient. The three stands in this case study were planted with red pine container seedlings at 800 trees/acre to ensure successful regeneration of a healthy, fully stocked, mixed red pine stand that would continue to provide future forest products and revenue to the school trust. Similar treatments have been published to the Silviculture Library and can be found linked here:

• Regenerating Bear Lake natural origin red pine using a mix of artificial and natural regeneration (MN DNR)
• Regenerating Blueberry Hill natural origin red pine using a mix of artificial and natural regeneration (MN DNR)
• Regenerating East Road natural origin red pine using a mix of artificial and natural regeneration (MN DNR)

Silviculture Objectives

Use both natural and artificial regeneration practices to regenerate a natural origin red pine site with characteristics that mimic a natural origin stand in structure and diversity, while maintaining red pine as the dominant species.

Pre-treatment stand description and condition

Stand establishment and management history

Around 1898-1900 these stands were established through some catastrophic disturbance event. Stands were thinned several times over the last 50 years, the last of which was in 2000 (stand 78) and 2009 (stands 48 & 213). There were no noticeable differences between the three stands as far as the conditions or treatment responses; thus the stands are aggregated and referred to as a single unit. 

Figure 1: Aerial photo view of the treatment area. The three stands are outlined in red; stand 78 to the south, and stands 213 and 48 to the north and northeast, respectively. 

Pre-treatment species composition

Stands were dominated by red pine averaging 43.9 cord/acre with scattered white pine, white spruce, trembling aspen, large-tooth aspen, red oak, paper birch, red maple, sugar maple, white cedar and balsam fir with a heavy hazel brush understory.

Pre-treatment forest health issues

All three stands had significant signs of Diplodia shoot-blight damage on advanced regeneration.

Landowner objectives/situation

Minnesota’s Permanent School Fund receives income from economic activities on School Trust Lands which are managed by the MN DNR. Revenue on School Trust Lands is generated from forest management amongst other activities. Forest management activities on School Trust lands are planned and carried out by MN DNR.

As it relates to forest management on School Trust Lands, MN DNR has the authority and responsibility to achieve the goals outlined in Minnesota Statute, Section 84.027, Subd. 18 including:

• manage efficiently and with undivided loyalty;
• reduce operating expenses and maximize revenues deposited in the Permanent School Fund;
• maximize long-term economic returns while maintaining sound natural resource conservation and management principles;
• balance short-term revenues and long-term interests so that long-term benefits are not lost in an effort to maximize short-term gains;
• maintain the integrity of the trust and prevent the misapplication of its lands and its revenues.

Silviculture Prescription

• Clearcut with reserves final harvest on 19 acres, removing red pine, white spruce, aspen, birch, red maple, sugar maple and balsam fir.
• Reserve all white pine, red oak and white cedar.  Reserve all non-hazardous snags.
• Broadcast full-tree skidding during dry, non-frozen soil conditions to set back the heavy hazel brush and scarify the site for regeneration.
• Pile slash and chip or burn piles to remove as much of the Diplodia inoculum on cones and slash as possible.
• Following harvest plant stands to red pine at 800 trees/acre. 

What actually happened during the treatment

The final harvest on this site took place in June 2018, removing 835 cords of red pine, 32 cords of northern hardwood, 21 cords of aspen, 6 cords of white spruce and 5 cords of balsam fir.  The operator did a decent job providing consistent scarification across the site during full tree skidding operations.  The slash was tightly piled at landings using a stroke delimber.  Piles were burned fall of 2018. In spring 2019 portions of the site were slash raked to provide additional scarification where whole tree skidding was limited by terrain or was insufficient. The stands were planted to red pine at 800 trees/acre with 1-0 PRT containerized seedlings. Mechanical brush saw release of conifer seedlings occurred in December 2020 in partnership with DNR Wildlife. A second brush saw release was completed in September 2023. Mechanical release was chosen instead of herbicide to help retain red oak, aspen, birch, maple and other species of diversity on site, but in a more intermediate/co-dominant canopy position in the future.

Post-treatment assessment

Tables 1 and 2 below outline crop tree and competition responses 1 and 4 years after harvest. 

Table 1: Fall 2019 regeneration survey with density and stock by crop and competition species.

Table 2: Fall 2022 regeneration survey with density and stock by crop and competition species.

The site has several large scattered residual red pine reserved in patches along edges, scattered white pine, white spruce, red oak, white cedar along with clumps of residual mature aspen/birch and clumped advanced regeneration of mixed balsam fir/white pine and mixed aspen/birch.

Figure 2: A view of Stand 78 in October 2023 after brush saw release the month prior. 

Figure 3: A view of stand 213 in October 2023 after brush saw release the month prior. 

Figure 4: Another view of stand 213 in October 2023 after brush saw release the month prior. 

Figure 5: Variable density natural white pine mixed with planted red pine, taken in October 2023 after brush saw release the month prior.

Plans for future treatments

Monitor stands with future regeneration surveys for possible subsequent brush saw release.

Costs and economic considerations

Revenue: final harvest $55,333.43 or $2912.29/acre.

Site prep - slash raking:  DNR dozer 23 hours for $1380 ($73/ac). 

Planting: 

• Labor- $1322.40 or $69.60/acre
• Seedlings- $2,416.80 or $127.20/acre
• Total planting cost of $3,739.20 or $196.80/acre.

Brush saw release:  leaf-off brush saw release completed December 2020, in partnership with DNR Wildlife who covered the cost of $145/acre. Leaf-on brush saw release completed in early September 2023 $168.70/acre.

Total regeneration costs: $11,079.47 or $583.13/acre.

Climate adaptation considerations

Increase stand resilience to climate change through increased species diversity.

Other notes

This case study was reviewed by MN DNR ECS and Silviculture Program Staff Chris Gronewold, Michelle Martin, and Mike Reinikainen. Case study submitted on 02/06/2025.

Summary / lessons learned / additional thoughts

This prescription balanced economic and ecological objectives by using a silvicultural strategy that favored both artificial and natural regeneration of red pine. It used leave tree retention, passive site prep that relied on timber harvest operations, supplemental scarification, planting, natural seeding and advance regeneration to achieve the desired results. Early results indicate that compositionally this stand is on track to the specified desired future condition, but future tending and monitoring will be needed to ensure the long-term success of the prescription. 

Now that we have implemented this type of prescription on several different sites (see linked Silviculture Library entries for Bear Lake, Blueberry Hill, and East Road) we are finding better results delaying planting 1 growing season and implementing a mechanical site prep technique such as disc harrowing, slash raking or anchor chaining. We have started prescribing a late summer mechanical site prep prior to planting the following spring to get better control of the competition on site and provide a better seed bed for planting and natural seed opportunities. 

Observations have shown that even with good mechanical site prep for scarification and competition control, seedling survival varies greatly across the site based on the response of competition after site preparation. This removes the need for variable density planting to achieve natural-looking regeneration conditions.