This case study describes the results of a red pine and white pine seed tree system initiated in 2003. 110-year-old red and white pines were reserved from harvest in a scattered distribution at a rate of around 7 seed trees per acre. The treatment was conducted in late fall just before freeze-up using conventional logging equipment; during harvest the feller-buncher cut back the shrub layer and random full-tree skidding was used to scarify the seed bed. A low-density planting of red pine seedlings was conducted early in the growing season after harvest to increase the likelihood of red pine regeneration and to augment natural regeneration. Shrub layer competition was knocked back with an herbicide treatment in the second growing season following harvest. The stand was fully stocked in 2018 with an average of 4236 seedlings per acre (coefficient of variation = 73%). Composition was a mix of white pine (42% of total seedlings per acre), red maple (27%), paper birch and other hardwoods (11%), red pine (10%), and other conifers (8%).
Naturally regenerate even-aged red and white pine cohort using a seed tree system, augmented with low density planting, and passive scarification with a conventional harvest operation. Account for costs of reserving seed trees from harvest. Tend the stand to promote early-successional bird habitat.
Pre-treatment stand description and condition
Stand establishment and management history:
Natural regeneration occurred in 1910-1911 following the initial cutover of the mature red pine canopy at Cloquet Forestry Center. The stand was thinned using hand-felling and cable skidding in 1962-3, 1973, and 1994. The 1962-3 treatment focused on removing jack pine and aspen. The 1973 and 1994 were free-thinnings of the majority-red pine canopy.
Pre-treatment species composition:
Composition was primarily red pine. Other compositional associates included white pine, jack pine, scotch pine, white spruce, balsam fir, red maple, paper birch, and aspen.
Pre-treatment growth and stocking:
Pre-harvest volume was estimated to be 45.8 cords per acre. At least 70% of the volume was red pine with smaller amounts of white pine, scots pine, aspen, balsam fir, white spruce, and paper birch. A majority of volume was of sawlog quality with additional amounts of utility poles and cabin logs, and bolts and pulp.
Pre-treatment forest health issues:
There were no known forest health issues in the pre-treatment stand. In the prescription record, seed crop, seed bed, drought, and sphaeropsis shoot blight were mentioned as concerns for using the seed tree system in this stand.
The objective of this prescription was to regenerate the stand to even-aged mixed conifers, primarily a mix of red and white pine, using a seed tree system.
Harvest red pine, Scots pine, jack pine, white spruce, balsam fir, red maple, and aspen. Reserve all eastern white pine and approximately 8 red pine seed-trees per acre, this is roughly 75' between trees. Reserves were intended to be kept indefinitely as seed trees and structural features.
No harvesting until October so that the brush would be more brittle, creating more breakage.
Harvest before soil freeze-up - To allow maximum soil disturbance. For seedbed preparation and possible increase tree stress by damaging surface feeder roots of the seed trees, stress can be beneficial in producing seed.
Full-tree Skidding - To maximize brush breakage. To disturb soil surface scarification to prepare the seedbed preparation.
Random Skidding - Skidder operators were instructed to skid over the entire sale area to cause as much to understory brush yet minimize damage to advanced conifer regeneration.
An augmentation planting of 220 seedlings per acre, 5000 total, 6 cu. in. containerized red pine, were planted by UMN students in the spring after harvest.
Allow two growing seasons for competition to resprout before completing an herbicide treatment for competition control.
What actually happened during the treatment
All treatment was performed as primarily as prescribed. The timber sale was purchased by Bell Pole and the harvest was conducted by Berthaiume Logging, Inc. between November 4 - 21, 2004. The total harvest volume was approximately 876 cords, with some additional volume sold in linear feet as cabin logs. Red pine sawlogs made up 62% of the harvested volume. Utility poles and cabin logs, bolts, and pulp made up the rest of the volume.
The post-harvest assessment found 154 trees reserve in this stand - approximately 8.3 trees per acre. The reserves were 50% red pine and 50% white pine. Retention represented a harvest volume loss of 32.05 mbf (approximately 70.5 cords) and a financial loss, or reduction of potential revenue, of $4968 ($155/mbf). The revenue left in a stand for regeneration purposes is not typically considered in seed tree systems because the overwood (seed trees) is supposed to get harvested once regeneration is secured. This prescription chose to not do an overwood removal in order to retain some mature trees in the stand. To account for this, they retained a slightly lower number of seed trees than typically called for in a pine seed tree and also chose moderate value, rather than high value, individuals.
The post-treatment assessment found a total of 154 reserved trees, 77 were red pine and 77 were white pine. This was an average of 6.7 reserved trees per acre. A few seed trees were knocked over (uprooted) by a windstorm that came through on June 30, 2004.
The competition control herbicide treatment was conducted on August 16, 2005. It used a skidder-mounted sprayer to apply Cornerstone (active ingredient of glyphosate) at a rate of 0.375 gallons per acre.
A June 2006 regeneration survey by undergraduate seasonal staff using 20 1/100-acre plots found total regeneration to be 1595 seedlings per acre. Red and white pine represented 6 and 9% of regeneration, respectively, in this survey. Red maple and balsam fir represented the bulk of the regeneration at 47% and 24%, respectively. This assessment suggested only 6% of planted red pines survived. The author is skeptical of these results given present-day regeneration numbers (see below) and the systematic arrangement of red pine, which suggests they were of planted origin. He suspects a combination of the inexperienced surveyors and the young pine might have caused the pine to be overlooked during the sample.
The author recalls sampling this stand during the UMN Advanced Field Session Resource Assessment class during May 2013. Anecdotally, he recalls sampling a rough 50-50 mix of pines and hardwoods and that the pines were typically knee height and below. Unfortunately, those and most of the survey results from a majority of other classes to sample over the years were not kept.
A regeneration survey using 29 1/500-acre circular plots was conducted in 2018 by students which found 100% stocking and an average of 4236 seedlings per acre (Coefficient of variation = 73%). See the table below for regeneration by species.
|Species||Seedlings per acre||Coefficient of variation (%)|
|Other conifers (balsam fir, white spruce, and Scots pine)||347||265|
|Other hardwoods (mostly paper birch with some northern red oaks)||458||151|
The relatively high number of species and coefficient of variations suggests relatively both a heterogeneous composition and variable spatial arrangement of seedlings.
During the fall of 2018, we collaborated with the American Bird Conservancy to conduct an early-successional habitat extension treatment on the eastern half of the stand. The goal was to promote horizontal and vertical heterogeneity of desired tree species. This consisted of a crop-tree release treatment with brushsaws. The prioritization list of species to be released included red pine, white pine, northern red oak, white spruce, paper birch, and red maple. Photos from the time of treatment suggest that a majority of trees were between 1-4 inches DBH and 8-12 feet tall.
Plans for future treatments
This stand is providing good early-successional habitat and will be left to grow until a first commercial thinning treatment. It is expected to be assessed for a first commercial thinning around 2035 (30 years following planting).
This stand is adjacent to some of the CFC’s prescribed burn units. We may consider restoring occasional surface fire as a community component of this stand, as it was assumed to have had prior to 1910.
Costs and economic considerations
Timber Sale Revenue: $63,116.68 ($3,411.71 per acre).
Revenue remaining in stand as reserves: $4968
Records of the costs for time to set up and administer the sale and planting and herbicide treatments were not available to the author.
Ron Severs, CFC forest manager 1972-2012, created and implemented this prescription. No herbivory protection strategies were used in this treatment.
As a University, we recognize the land on which we live, learn and work is the traditional, ancestral and contemporary lands of Indigenous peoples. We build upon this acknowledgment and work to improve and strengthen our relations with the 11 sovereign Tribal Nations of Minnesota, most recently by creating the Native American Promise Tuition Program. The Cloquet Forestry Center is on lands reserved by the Fond du Lac Band of Lake Superior Chippewa in the 1854 treaty of La Pointe. We benefit from the long-term land stewardship of contemporary indigenous people and their ancestors. We are building on this acknowledgement through relationship development and collaborating on ecoculturally significant ishkode restoration.
This case study was developed with support from the United States Department of Agriculture's National Institute for Food and Agriculture, Renewable Resources Extension Act. Project #2021-46401-35956, principal investigator Eli Sagor, University of Minnesota.
Climate Adaptation Considerations
The planning for this prescription occurred in 2003. Climate change was known to managers, but recommendations and strategies for resilience were not yet developed. As such, climate change did not affect the prescription. However, the compositional diversity created by the treatment suggests that the stand will have both ecological and economic resilience moving forward, characteristics that are often incorporated into climate adaptation treatments.
Summary / lessons learned / additional thoughts
This prescription suggests that patience is a virtue that foresters need to value, especially when it comes to natural regeneration. This stand is fully stocked, well on its way to maturity, and with a resilient diversity of structure and composition. We have at least nine species regenerating at meaningful numbers across the stand. The CV numbers suggest that regeneration is relatively heterogeneous (patchy or variable are other potential words); I use 30-50% as the boundary between homogeneous and heterogeneous, respectively. For the first 8-10 years following harvest, the regeneration numbers were quite low, especially for pine, and there was a lot of discussion about this being a "Failed" treatment. However, over the following 5-8 years, the regeneration numbers and visible growth seemed to explode. The white pine trees have been putting on between 15-30 inches of height growth per whorl in recent years. This suggests that they were biding their time, potentially investing in root growth, and shot up past browse height quite quickly. There is a potential that herbivory protection and further competition reduction treatments could have encouraged pine to have their growth spurt earlier than 10-12 years following harvest.
We consider this treatment to have been generally successful when considering a broad goal of even-aged mixed conifer regeneration. There is more hardwood representation than anticipated and less red pine. The red pine density of 400 trees per acre on average (CV = 160%) is approximately 1.5 times higher today than what was planted in 2005 and only about 10% of the total regeneration. It is not totally clear why red pine did not regenerate as well as other species. It could have been that there was not sufficient soil scarification or competition reduction, that the seed available was not sufficient due to not matching a good seed year or not sufficient seed trees, or that there was too much competition for light or soil resources. It is important to note that this stand has not seen fire since approximately 1905. It could be that 100 years of not fire, which supports non-pyrogenic plant and soil community members, left the soil with a lack of biotic and abiotic associates and resources that benefit red pine. If we return surface fire to this community, I expect that the health and relative representation of red pine and other pyrogenic species, such as blueberry, to be improved. In the absence of surface fire, I expect the more mesophilic community members, such as white pine, to maintain their relatively higher representation.
Supplemental content document for the case study with further graphics.
Kyle has been the CFC forest manager and research coordinator since 2015. He enjoys exploring stand development, silviculture, and the inherent biases that we bring to decision making. He feels it is important to see himself and other humans as community members of forested and non-forested ecological communities.