Observations/Conclusions in 2019 (23 years post-treatment)
The treatment was largely successful, resulting in a healthy and diverse central hardwoods stand
The current stand is a healthy, diverse 23 year old northern and central hardwood forest that is a good ecological fit for the site. Therefore the silvicultural treatment was largely successful.
We did not get as much oak regeneration as we had hoped for
While there is a small component of 23 year old oak in the current stand that regenerated post-harvest, we were hoping for considerably more of it. Most of the oaks present in 2019 are harvest residuals. 1998 regeneration survey data indicates that some young white oaks did regenerate immediately post-harvest, however they are not part of the young forest canopy in 2019. This indicates that they got out-competed by other vegetation in years 3 through 10 after harvest, and also possibly had animal predation (deer browse) issues.
As shown in table 2, in 2019 oak had greater total basal area, relative basal area, and frequency on plots than basswood and black cherry, however, this was due to the larger diameter oak residuals left over from the harvest. Oak harvest residuals (those greater than 10 inches in diameter, plus half of the red oak BA from 5-10 inches in diameter) account for 20% of the total stand basal area. In contrast, oak regenerated post-harvest (all 3-5 inch DBH oaks, and half of the 5-10” red oak BA) account for only about 3% of total stand BA.
Frequency data for oaks regenerated post-harvest also indicates very modest oak presence:
- 3-5 inch DBH red oaks were only present on 8% of our plots.
- 5 to 10 inch red oak BA were on 16.67% of plots, but since we estimated that only about ½ of the 5-10 inch DBH red oaks were established post-harvest, that is only about an 8.3% frequency.
Table 3: Tree species basal area in feet2/ac by DBH class in inches in 2019. Frequency refers to percent of plots containing trees within the class
Intermediate stand treatment (release) and possibly protection from animal browse would have been necessary for more oak to survive
Regeneration data three growing seasons after harvest indicated 115 white oak/acre averaging 4 feet in height. Therefore it appears that at least some white oak regeneration did get established early on, but almost all of it got outcompeted and shaded out in the years since. It seems clear that additional post-harvest release treatments would have been necessary to better achieve the oak regeneration objective. This finding is consistent with guidance information for the MHs 37 NPC, which indicates that oak can generally become established, but struggles to get above competition from other woody vegetation and becomes shaded out. It is also well documented that young oaks are tasty deer food, and therefore deer browse is commonly a big factor keeping oak from successfully competing.
Table 4. Results of a September 1998 regeneration check (3 growing seasons after harvest)
Species Avg. Stems/Ac Avg. Height (ft.) Stocking %
Black Cherry 769 10 85|
Basswood 327 5 54
Aspen 404 8 23
White Oak 115 4 46
Elm 288 5 54
Boxelder 77 4 31
Buckthorn 404 6 54
Note that there was some white oak regeneration post-harvest. Most of it did not survive to be a part of the current stand.
One question that might occur to readers is whether planting oaks to supplement natural regeneration would have resulted in better success on this site. While we can’t know for sure, we do know that some natural oak stems did become established post-harvest, but got out-competed by other vegetation in years 3-10 or so. It therefore seems likely that planted stems would have met a similar fate.
The stand has a good component of healthy, well-formed black cherry
One unexpected positive outcome of the treatment is that there is a good component of healthy, well-formed black cherry in the current stand. This is interesting because in the observations of the author while in the field in the 1980s and 1990s, most black cherry tended to have crooked stems, thin crowns and major heartrot. Many were infected with black knot disease. On most sites, cherry struggled to reach 14 inches DBH before dying. Time will tell whether the black cherry on this site (and a number of others observed during case study field work in 2019) will reach maturity in healthy and merchantable condition, but it is definitely off to a good start after 23 years. There is some black knot disease and stem cankering on the cherry, but it appears to be present on less than a third of the stems. Of note for forest managers, the NPC guidance for MHs 37 indicates that black cherry may need some intermediate release to reach heights much above 10 meters. Many of the cherries on this site are already 10 meters or more now, but it will probably be worth monitoring in the future to see if their crowns and health begin to deteriorate.
One reason for the improved form and health may be that the current black cherry was established and grew in nearly full sunlight after the clearcut with reserves harvest. This is in contrast with the partial-shade establishment and growth conditions that were probably the case for the previous generation, requiring their struggle for sunlight through partial shade. Another possible reason for better black cherry health and form could be the somewhat warmer and wetter climate experienced over the past several decades.
While 2019 data for regeneration less than 3 inches DBH in Table 3 is not a big part of the “lessons learned” for this study, we include it because it can still be of interest to managers moving forward.
Table 5. Tree regeneration density (average stems/acre) in 2019. Regenerants: <1 foot in height; Seedlings: > 1 foot in height and less than 1” DBH; Saplings: > 1” DBH and < 3” DBH;
We did not gather understory plant data for this stand, but from observations on a similar adjacent stand, the understory plants looked typical for mesic hardwoods stand in this part of MN.
There is a significant amount of buckthorn on the site. We should note that it is pretty common to find buckthorn at high levels in this part of Goodhue County. There was also some Japanese Barberry present.