Overview
This case study looks at the differences in northern red oak regeneration in three scenarios: regeneration under reserved standing oak, regeneration in gaps 100 feet across, and regeneration in gaps 200 feet across. Northern hardwood and oak stands are an important part of logging and industry within the central Minnesota area; oak harvested from these stands is sawn into boards to be used for wood products such as pallets, flooring, and decking as well as being used in other wood products such as firewood or chipped to be used in mulch or biomass plants.
This case study focuses on how well the oak is regenerating within the different sized gaps created within the stand as well as surveying regeneration underneath the mature oak. This data can be used for silvicultural practices for oak hardwood stands as well as paper birch as we discovered there was significant paper birch regeneration within the gaps along with red oak. The area harvested was 11 acres in the gaps and the skid trails within the 36 acre treatment area.
Silviculture Objectives
The objective for this stand was to create gaps of different sizes in rows to create a new age class and promote regeneration of oak while also retaining features such as species mix and structure. The oak within the stand is estimated to be 100 years old and showing decline with the overall goal of creating three age classes. This gap harvest has already created the first age class with two future harvests in the future to reach this objective. Sections of old forest growth features are to be reserved. Ephemeral pools and wet areas within the stand are to be reserved for salamander habitat.
Pre-treatment stand description and condition
Stand establishment and management history
Prior to DNR acquisition, the stand was an even aged jack pine plantation, which was clearcut once acquired in 1916, leading to the 100-year-old even-aged northern red oak currently on site. This is backed up by the fact that we saw old jack pine trees close together on the northern edge of the stand close to Roger’s Lake. LiDAR suggests that before the jack pine, the Rogers Lake area was settled and used as a farmstead with a structure nearby. The land at that point was likely used for grazing and possible burning.
Pre-treatment species composition
Even-aged northern red oak.
Pre-treatment growth and stocking

Figure 1: data of the stand 1 year prior to harvest.
Pre-treatment forest health issues
Oak decline due to old age
Porcupine damage
Landowner objectives/situation
Generate revenue, regenerate oak to perpetuate northern hardwoods via gap cuts within stand and create multiple age classes.
Silviculture Prescription
The prescription was to establish an uneven-age structure of oak to address the oak decline and meet plan and coordination objectives. The preliminary prescription code is 1300 – Uneven-Aged Regen Harvest. A string of pearls cut with 100’ and 200’ gaps along skid trails would provide sunlight and scarification for oak germination. Harvest would take place in the fall when oaks and birch are dropping their seeds and scarification from the logging would be obtained. Without management the stand would likely succeed to sugar maple and ironwood and due to thin soils management for sugar maple would not be recommended.
What actually happened during the treatment
Cutting commenced on 10/20/2022 after pre-sale meeting on-site few days prior. Several formal and informal inspections occurred over the next month between CTP Chipping Inc and the forester to make sure everything was going well. Loggers had concerns with the string of pearl cuts, which is another term for gap cuts along a skid trail, and how accurate they were with their Avenza map and the center trees on site. Many caution hauling signs were put up as logging and hauling operations were near a busy ATV trail. The spec for the road width was 25’ in the permit but it ended up being between 35-40’ and resulted in liquidated damages. CTP Chipping Inc paid for the added timber caused by the widened road. By 11/14/2022 the road had frozen while the site itself had not and was holding up and the skidder operator was instructed to put slash in the ditches for erosion control. In the end everything looked fine and site operations were wrapped up on 11/22/2022. On 7/25/2023 the road was closed out and water bars and cross drainage had been established.

Figure 2: A view of one of the "string of pearls" created in the study.
Post-treatment assessment
One and a half growing seasons after the initial cut, we entered the site and collected data on 36 plots to determine what tree species were regenerating within the different sized gaps and the remaining overstory trees. 12 plots each were created for the 100-foot gaps, 200-foot gaps, and the oak overstory plots. Regenerants (trees <1” dbh and under 1’ tall) and seedlings (trees <1” dbh and over 1’ tall) were surveyed within a 1/500th acre area. Saplings (trees 1” to 3” dbh) and small trees (trees 3” to 5” dbh) were surveyed within a 1/100th acre area. Both groups were measured using a high pile stick with a pink wire flag at plot center. The tree block section was measured using a 10-factor prism. Each group was then tallied by species and number within the survey area. The results are seen in tables 1, 2, and 3, comparing the 100-foot, 200-foot, and oak overstory plots. Figures 3 and 4 show the different TPA values for the surveyed species within the regenerant and seedling blocks as these were the focus of this study.
Table 1: TPA per Species and BA for Tree Block for 100ft Gaps
Species | Regenerate Block TPA | Seedling Block TPA | Sapling Block TPA | Small Tree Block TPA | Tree Block BA (ft2) |
Northern Red Oak | 5000 | 875 | - | - | 15.8 |
Paper Birch | 2500 | 5291 | - | - | - |
Red Maple | 1708 | 333 | - | - | - |
Sugar Maple | 625 | 1666 | - | - | 1.6 |
Bigtooth Aspen | 41 | 833 | - | - | - |
Quaking Aspen | - | 375 | - | - | 0.8 |
Basswood | - | 83 | - | - | - |
Black Ash | 41 | 166 | - | - | - |
Balsam Fir | 83 | - | - | - | - |
Ironwood | - | 41 | - | - | - |
Table 2: TPA per Species and BA for Tree Block for 200ft Gaps
Species | Regenerate Block TPA | Seedling Block TPA | Sapling Block TPA | Small Tree Block TPA | Tree Block BA |
Northern Red Oak | 4166 | 2583 | - | - | - |
Paper Birch | 1875 | 6666 | - | - | - |
Red Maple | 958 | 1166 | - | - | - |
Sugar Maple | 500 | 1166 | 8 | - | - |
Bigtooth Aspen | - | - | - | - | - |
Quaking Aspen | 41 | 416 | - | - | - |
Basswood | - | 333 | - | - | - |
Black Ash | 41 | 125 | - | - | - |
Balsam Fir | - | - | - | - | - |
Ironwood | - | 375 | - | - | - |
Table 3: TPA per Species and BA for Tree Block for Oak Overstory Plots
Species | Regenerate Block TPA | Seedling Block TPA | Sapling Block TPA | Small Tree Block TPA | Tree Block BA |
Northern Red Oak | - | 125 | - | - | 58 |
Paper Birch | - | - | - | - | 1.6 |
Red Maple | 1041 | 41 | - | - | - |
Sugar Maple | 2833 | 4375 | 100 | 41 | 20 |
Bigtooth Aspen | - | - | - | - | - |
Quaking Aspen | - | - | 8 | - | - |
Basswood | - | 41 | - | - | 23 |
Black Ash | 41 | 250 | 58 | 8 | - |
Balsam Fir | - | - | - | - | - |
Ironwood | 375 | 500 | 241 | 8 | - |
Yellow Birch | - | - | - | - | 0.8 |

Figure 3: Comparing TPA of the species surveyed within the regenerant block across all plot types.

Figure 4: Comparing TPA of the species surveyed within the seedling block across all plot types.

Figure 5: Abundant oak regeneration.
ECS Plant Community Monitoring
We conducted an ECS (Ecological Classification System) study to further understand the site and it was determined to be a MHN35 with moderate plant diversity. It is worth noting that the site has a heavy earthworm presence with little duff layer and large mats of Pennsylvania sedge (Carex pennsylvanica). We also found in box 512 (Supplemental Table 1) a small area that was wetter than the surrounding plant community which led us to gather many plants that are commonly found in wetter communities that are not found in other parts of the site. While we did follow the guidelines for how an ECS survey works, ours was mirrored to the one in Supplemental Figure 1, where our box one was where the north and west bearings meet instead of at the end of the western bearing. This ECS plant data may serve as baseline data of the diversity richness for the site to determine if the species diversity and richness will be maintained over the course of management to perpetuate the site as young regenerating oak hardwood forest.
A soil sample was also taken where the ECS data was collected on a side slope of 17%. The soil profile can be described as follows; 0-18” is sandy loam, becoming loamy sand from 18” to 26” in depth. Then from 26” the soil profile becomes sand. At 36” there was too much gravel and rock to retrieve any more soil.
Plans for future treatments
The goal is to create three age classes of regenerating oak. The first cut that occurred in the fall of 2022 created the first new age class. Two other future harvests are planned; however, the overstory red oaks are starting to show decline and the silvicultural plan may change. The final treatment may propose harvest of the existing residual oak forest while retaining scattered mature oak as seed trees and to maintain old forest characteristics. The reserved oak seed trees would ensure the success of the oak regeneration second treatment by maintaining an oak seed source and may eventually become standing dead and coarse woody debris.

Figure 6: Co-author Chris Brussat taking measurements.
Costs and economic considerations
No costs were put towards site prep or road work on the DNR’s end. The timber on the site had an appraised quantity of $45,016.06 as mixed species and calculated by a volume of 6,883.19 tons to be used as biomass. The scaled quantity was 5,794.87 tons and valued at $37,898.45, a -15.81% difference with the DNR paying the permit holder (CTP Chipping Inc.) a refund of $7,117.61.
Climate adaptation considerations
According to the Climate Change Atlas from the US Forest Service, northern red oak (Quercus rubra) is rated as “highly adaptable to a changing climate and thus its overall capability is very good.” Oak wilt (Bretziella fagacearum) has been detected in central and south-eastern Minnesota and with climate change it is predicted to increase its range north into Carlton County where it is currently not found but at significant risk (MN DNR). Capturing the most value from the stand and regenerating the oak to young resilient forest before oak wilt infestation occurs on site is important for future economic and ecological goals.
Other notes
Canopy closure within the overstory oak plots was estimated at 81% with an outlier of one plot being 50% closure likely due to edge affect and wind damage. Within this plot there was a strong hazel establishment due to more light reaching the forest floor.
Forest health concerns around encroaching plants include an established population of thistle (Cirsium sp.), areas of heavy amounts of black bindweed (Fallopia convolvulus), and areas of heavy amounts of Pennsylvania sedge (Carex pennsylvanica). These species, if allowed to dominate the stand, can contribute to regeneration issues. As levels of these species are considered moderate at this time, no treatments of these species are planned. We will continue to monitor the situation at the future 3, 5, and 10 year regeneration checks.
Many types of wildlife were seen in or near the stand such as turkeys, black bears, and white-tailed deer, all likely utilizing the oak component of the stand for forage and habitat. It is believed that this first treatment so far has increased mast production of the existing red oak and increased the quality of habitat for the above game species.
For both the 100- and 200-foot gaps, every third plot we measured the length of the gap itself to see how accurately the logger was able to employ the gap harvest technique. We found that the average length of the 100 ft gaps were 101.75 ft with a standard deviation of 7.15 and the average length of the 200 ft gaps were 178.75 ft with a standard deviation of 9.55. This likely contributed to the fact that the scaled quantity was less than the appraised quantity since the 200-foot gaps were over 20 feet smaller than they should have been and when compounded across all the 200 foot gaps, there were many overstory trees that were not harvested as the logger underestimated the gap size for the 200 foot gaps.
The stand exam includes adjacent smaller stands that were merged into this one in the forest inventory. That is why appraised acres are higher than the planned acres for this stand. The area harvested was 11 acres in the gaps and the skid trails within the 36 acre treatment area. For the sample design we used one plot per acre in the 36 acres. We allocated 12 plots for each of the 3 treatment types: 2 different gap sizes and the residual oak forest reserved.
Summary / lessons learned / additional thoughts
When looking for oak regeneration, the 100 ft gaps provided more regenerants (5,000 TPA) than the 200 ft gaps (4,166 TPA) while the oak overstory plots had no oak regenerants. However, when looking at the seedling block, although overall lower than regen seen in the regenerant block, oak seedling regeneration was higher in the 200 ft gaps (2,583 TPA) than the 100 ft gaps (875) while the oak overstory saw only a few seedlings (125 TPA). This leads us to believe that the oaks regenerate better in the 100 ft gaps as there is less light than the 200-foot gaps, allowing the more intermediate shade tolerant oaks to compete better with other species that are more shade intolerant. As seen from the tables and charts, birch seedlings dominated the 100- and 200-foot gaps and outnumbered the oak seedlings. Paper birch was appraised at 210 cords prior to the cut in the fall and when looking at the current stand, there are very few birch seed trees remaining among the other overstory trees. We speculate that even though there were fewer birch trees than oaks, the harvesting of this site created ideal conditions for birch regeneration as the harvest took place in the fall when the birch trees were dropping their seeds and the skidding created scarification on the land which is vital for both birch and oak regeneration. Birch trees are more prolific seeders than oaks and it may also be possible that there were additional birch seeds in the seed bed waiting for the right conditions to germinate, however we do not know how long birch seeds can persist within the seed bed, so this is merely an assumption. Birch is also a more aggressive competitor and a faster growing species than northern red oak. Paper birch is shade intolerant while northern red oak is classified as intermediate in shade tolerance which explains why we see more paper birch seedlings in the 200-foot gaps than the 100-foot gap as they are faster growing.
As predicted, there was very little oak regeneration underneath the overstory plots where more mesic and shade tolerant species were seen such as sugar maple and ironwood, emphasizing the importance of creating patches of disturbance or gaps where oak regen can have the sunlight and mineral soil contact necessary to regenerate oak. We found that 100-foot gaps (or 0.18 acres) are the ideal gap size for regenerating northern red oaks without allowing too much light to hit the ground and favor more shade intolerant species. If there are prolific seed trees such as birch on the site or nearby as their seeds can travel long distances, it should be put into consideration if harvest takes place in the late summer of fall as the conditions that help with oak germination also help with paper birch germination. This site will be looked at again at 3-, 6-, and 10-year intervals to update how well the birch and oak are competing and see if treatment is necessary to release any oak regen being suppressed by paper birch. After 10+ years when desired oak and paper birch regeneration are free to grow above the competition and deer browse height the second stand treatment can begin to be planned.
Supplemental content
Supplemental Table 1: ECS data worksheet from within the oak overstory section of the stand.
Species-area Plot Worksheet | Version 1.1, June 2019 Ashlee Lehner | NPC Code: MHN35 | |||||
Name: Cassandra Baysal, Wes Habedank, Chris Brussat, Chris Roy, & Brenna Roth | Date: 07/15/2024 | ||||||
Coordinates of Origin | Azimuths of baselines | ||||||
Easting: Northing: | Baseline 1 (squares): 0 degrees | ||||||
Lat: 49֯ 42’ 55.7” Long: 92֯ 46’ 43.1” | Baseline 2 (rectangles): 270 degrees | ||||||
Comments: | Probably a worm heavy site | ||||||
Wet hole (5 ft area) in NW corner of box 512 | |||||||
ê Area | ê Species | 512 | Beaked Hazel | ||||
1 | Ironwood | 512 | Bunchberry | ||||
1 | Canada Mayflower | 512 | Hawkweed | ||||
1 | Large Flowered Bellwort | 512 | Alternate-leaf Dogwood | ||||
1 | Sessile Bellwort | 512 | Bush Honeysuckle | ||||
1 | Pale Vetchling | 512 | Unknown Grass 2 | ||||
1 | Wild Sarsaparilla | 512 | Unknown Sedge 1 | ||||
1 | Violet Sps 1 | 512 | Water Hemlock | ||||
1 | Pennsylvania Sedge | 512 | Joe Pye weed | ||||
1 | Mountain Rice Grass | 512 | Northern Bugleweed | ||||
2 | Bigtooth Aspen | 512 | Pyrola sps | ||||
2 | Maryland Black Snakeroot | 512 | Dwarf Raspberry | ||||
4 | Juneberry | 512 | Bladder Sedge | ||||
8 | Sugar Maple | 512 | Mint sps | ||||
8 | Large leaf Aster | 1024 | Beard Short Husk | ||||
8 | Starry False Solomon’s Seal | 1024 | Unknown Grass 3 | ||||
16 | Wood Anemone | 1024 | False Miele | ||||
16 | Rose Twisted Stalk | 1024 | Unknown Fern 1 | ||||
16 | Aster Sps 1 | 1024 | Wooly Weet Cecily | ||||
32 | White Spruce | 1024 | Side Flower Aster | ||||
32 | Star Flower | 1024 | Round lobe Hepatica | ||||
32 | Red Maple | 1024 | Dandelion | ||||
32 | Hairy Solomon’s Seal | 1024 | Downy Arrowwood | ||||
32 | Paper Birch | 1024 | Sweet Scented Straw | ||||
64 | Red Oak | 1024 | Basswood |
| |||
64 | Balsam Fir | 1024 | Red Baneberry |
| |||
64 | Partridge Berry | 1024 | Spikenard |
| |||
128 | Spreading Dogbane | 1024 | Unknown Goldenrod 2 |
| |||
128 | Zig zag Goldenrod | 1024 | Quacking Aspen | ||||
128 | Downy Yellow Violet | 1024 | Unknown Grass 4 | ||||
128 | Bearberry | ||||||
128 | Blue bead Lilly | ||||||
128 | Shining Fir Moss | ||||||
128 | Aster/Golden Rod Unknown 1 | ||||||
256 | Leatherwood | ||||||
256 | Lady Fern | ||||||
256 | Unknown Grass 2 | ||||||
256 | Fly Honeysuckle | ||||||
512 | Blue Flag Iris | MAIL COMPLETED FORM TO: Matt Huseby ECS Program 483 Peterson Road Grand Rapids, MN 55744 218-322-2509 | |||||
512 | Horsetail | ||||||
512 | Red Raspberry | ||||||
512 | Black Ash | ||||||
512 | Ground Pine | ||||||
512 | Running Club Moss | ||||||
512 | Chickweed | ||||||

Supplemental Figure 1: Layout of a typical ECS study.