The silvicultural prescription of pre-harvest underplanting, a clearcut with reserves harvest, and crop-tree release about 10 years after harvest has been successful on this site.
14 years after initial treatment, there is a mixture of desirable hardwood regeneration that is a good ecological fit for the site, including a good oak component. A fair number of these seedling and sapling stems are above deer browse, with some clearly at “free to grow” status.
In addition to the oak and walnut, there is a significant amount of regeneration of other desirable hardwood species, including hackberry, basswood, shagbark hickory, black cherry, and (on some parts of the site) sugar maple.
This stand is well on its way to reaching species composition objectives: mixed hardwoods with a good component of oak, with high timber and wildlife value.
The crop tree release work 10 years after harvest was critical for allowing oaks and other desirable shade-intolerant species to survive and thrive. An earlier release may have been even better.
One “lesson learned” from MNDNR forester and co-author Jason Bland is that perhaps doing a regeneration check and crop tree release on this site earlier, within the first few years after harvest, would have resulted in even more oak regeneration survival.
We aren’t completely certain why more oak regeneration is growing past deer browse height on this site than on other, seemingly similar, sites
No browse protection practices were employed on the site, yet a significant amount of oak regeneration is in the process of reaching heights above deer browse levels.
Larger-than-average harvest area size and deer hunting pressure seem to be likely factors, but may not be the entire story. A third possibility is that the site may have had exceptionally good natural regeneration establishment after the timber harvest. We think a worthy subject for future research might be to obtain historical deer population data to see if anything related to oak regeneration success over the years could be learned from that.
We aren’t certain why the strategy of no vegetative competition control for the first 10 years after underplanting and harvest worked on this site, but has failed on other, seemingly similar sites
Good oak planting stock is a likely factor but there must be others, including the possibility that an exceptionally high amount of natural regeneration may have become established after the timber harvest. We will continue to seek answers to this question in future case studies.
More case studies and research on oak underplanting are needed
We asked ourselves what factors about this site caused the strategy of underplanting, harvesting, and crop tree release after 10 years to adequately meet oak regeneration objectives? What does it have in common with other successful sites, and what is different about sites where this silvicultural strategy (with no vegetative competition control or deer browse protection in the first 10 years) has not worked?
While we have postulated some possible causal factors in this study, we don’t have conclusive answers to these questions. We suggest that more case studies and research would be valuable.