Advance Oak Regeneration
One major question we wanted to answer with this study was which treatment(s) worked best to produce advance oak regeneration of adequate size (> 4’ high) and stocking (> 60%) to ensure a desired oak component in the future stand.
As of 2021, it appears that there is not yet sufficient advance oak regeneration to proceed with a final shelterwood harvest. As shown in Figure 3, Figure 4, Figure 7 and Figure 8, the number and distribution of oak seedlings on all sites is good (stocking 100% for all treatments), but the large majority of them are still quite small.
Given that oak stocking on all sites is good, average height is the most significant factor to consider at this point, since larger, established seedlings have greater potential to recruit into larger size classes. Average height for oak is greatest on site 4 (herbicide site preparation, planted and natural regeneration) at 2.2 feet. Another observation is that the oak seedling numbers are higher on sites treated with prescribed burns, but the seedlings are very small. This is probably because of their younger age relative to the other sites.
From the data we have, and observations while collecting it, we feel there is not yet adequate advance oak regeneration over 4 feet in height on the sites to support a final harvest decision. An oak crop tree competition release is planned for the summer of 2022, using brush saws. This work is needed to enable adequate numbers of oak to grow above deer browse height and most vegetative competition.
We plan to gather regeneration data again in 2023 to enable a well-informed decision on timing of the final shelterwood harvest.
Vegetative Competition Control
Control of competing vegetation is critical for oaks to recruit into larger size classes. Sugar maple in particular can provide some of the most challenging competition.
As shown in Figure 4, treatments 3 (herbicide and mechanical site preparation) and 4 (herbicide site preparation) reduced sugar maple numbers the best so far. While there are still quite a few sugar maple stems on these areas, they are noticeably less dense as of 2021 than on the other treatment areas. Average sugar maple/acre is 600 and 767 respectively for sites 3 and 4. All other treatments have average maple stems/acre over 1,500/acre, with most sites over 2,000/acre.
We were somewhat surprised to see high sugar maple/acre numbers on sites treated with prescribed burns. It is possible that in spite of best efforts, conditions resulted in burns that were just not intense enough to kill most maple stems. With its relatively thin bark, maple is susceptible to control by fire, but the fire still needs to be intense enough to do so. However, it is challenging to have conditions (fuel, temperature and humidity) to enable hot enough prescribed burns to consistently control maple competition.
A note on the importance of coppice origin oak: Many of the taller stems of oak regeneration were of coppice origin. Stump sprouts can be an important component of total oak regeneration because their rapid juvenile growth enables them to grow above competing vegetation and deer browse susceptibility faster than seedling origin stems.
We gathered detailed baseline understory plant data in 2016 to enable assessment of treatment impacts to all plant species in the understory and overstory. We found plants to be consistent with those generally found in MHc36 plant communities.
We hope to gather similar data at future points in time and compare it to the baseline data to assess any impacts to understory plants.
We observed some Canada thistle after herbicide treatment in sites 3 and 4. This is typically a short-term phenomenon, with the thistle becoming outcompeted by other vegetation in time.
We also observed low levels of reed canarygrass in some locations, which is common in this area, on these types of sites.