Plant regeneration surveys occurred in 2014 and 2015. A comprehensive survey of the entire area was completed in 2016. Because the entire site was not surveyed prior to 2016, it is challenging to make any statements about regeneration as a whole immediately post-harvest. Group 7 had no management (but was relatively open prior to the 2013 harvest) and had the highest number of stems per acre for ash, cottonwood and elm out of all the surveyed areas (Figure 5).
Across all the areas surveyed in 2014 and 2015, ash and cottonwood appeared to do very well, while hackberry also established well on some of the sites. With cottonwood the only one of these species that was planted, and with the high densities, it can be assumed that most of this was natural regeneration. Oak and elm were also present in 2014 and 2015 at densities similar to the planting densities, indicating that survival in the surveyed sites was good. In addition, silver maple established in very high densities across all surveyed areas (Figure 6), with the exception of the shelterwood. The 2014 and 2015 surveys did not account for seedlings size, but it can be assumed that most seedlings in those surveys were small (< 1 foot tall), unless they were planted.
By 2016, the total number of seedlings per acre had decreased to an average of about 15,000, with less than 1,000 of those being greater than 1 foot tall (Figure 7). Overall, planted survival was low, with only swamp white oak, elm, and silver maple having any surviving seedlings in 2016 surveys (Table 2). Much of the maple regen may have been natural, so it is likely that mortality for planted silver maple was also high. No surviving walnut, cottonwood or river birch seedlings were found. The clearcut areas with forestry mulching and natural regen had the highest density of taller seedlings, though the large majority of those were ash, which are unlikely to survive to maturity due to emerald ash borer. The group selection areas with forestry mulching, herbicide and planting had the highest density of large seedlings that was not dominated by ash. These same areas also had the highest density of small seedlings (<1 ft tall), and these were heavily dominated by silver maple. The clearcut areas with forestry mulching, herbicide and planting had the next highest density.
Based on an assessment of all seedlings, the site is stocked at levels well above the target of 200 seedlings per acre. Larger seedlings provide a more reliable estimate of seedlings likely to survive, and when considering only large regeneration, the average across all plots is about 225 stems per acre (excluding ash). However, when considering planted species, only 163 stems per acre were noted in surveys. Regardless, due to the large cohort of natural silver maple and, to some extent, hackberry, the site is stocked above the target level as of the 2016 survey.
The data from the elm and swamp white oak comparison planting showed that there was no mortality in 2013. In 2014, mortality occurred in both species across all areas surveyed. Elm survival was higher compared to swamp white oak, even though more mortality occurred in elm seedlings. By 2016, elm survival was approximately 50% of planted seedlings, while oak survival was about 75%. Of the surviving seedlings, the average height was just above 1 foot tall for the elms and just under 1 foot for the oaks, indicating little to no growth in the three growing seasons following planting.
Deer herbivory was influential to survival and growth, with evidence of browse present on a vast majority of seedlings (Figure 6). The average seedling was classified as 25-50% of the twigs showing evidence of browse. Browse was noticeably higher in the shelterwood and group selection areas than in the clearcut areas. Silver maple and elm had the highest browse overall, though large swamp white oak and large elm showed high levels of browse (>50%) on all seedlings inventoried. No particular species, however, showed distinctly higher or lower levels of browse, indicating that deer were having a relatively uniform impact across all species.
In areas treated with herbicide, reed canary grass has been very effectively controlled, and vegetation is currently dominated by broadleaf herbaceous plants, such as stinging nettle and pigweed. In clearcut and group selection areas not treated with herbicide, reed canary grass remains dominant over large areas. In the shelterwood area there are patches of reed canary grass mixed with larger areas of native herbaceous vegetation.
It should be noted that the site experienced high water levels during much of the growing season in 2013 and especially in 2014 (Figure 9). High water occurred at times when floodplain trees drop seed and almost certainly would have had an impact on survival and growth of tree seedlings.