Mechanical damage incurred by underplanted northern red oak (Quercus rubra) following six overstory treatments and the development of planted northern red oak seedlings under closed canopy : first-year results

Regenerating oak, on recently harvested sites, continues to be a silvicultural challenge in the Central Hardwood Region. Enrichment planting can increase oak regeneration potential and success during the early stages of cohort development. In April of 2002, a replicated oak silviculture study using artificial regeneration was established near Oak Ridge, TN. High-quality, nursery-grown, 1-0 bareroot northern red oak (Quercus rubra) seedlings were underplanted prior to timber harvesting. Six overstory treatments, no cut (control), silvicultural clearcut, commercial clearcut, and 50, 25, and 12.5 percent basal area (BA) retentions, were implemented after planting, with each being replicated 3 times for a total of 18 overstory treatment units. Seedlings were assigned to harvest damage classes in order to assess the effect of operational damage on their survival. There were no significant differences in survival between the cutting treatments, but mortality as high as 83 percent (12.5 percent BA retention) suggested substantial losses due to harvesting. Twig damage differed significantly between cutting treatments (P<0.05). These results indicate that pre-harvest underplanting in mature stands similar to those treated in this study results in high seedling mortality and varying levels of damage, depending on harvest intensity.

The effects of site (landforms and vegetation), genetic family, and initial seedling morphology on seedling growth and survival under closed canopy were evaluated. There were some significant differences in seedling growth and survival between the control units (P<0.05), suggesting possible site effects. Genetic family differences for seedling survival occurred (P <0.05), but not for seedling growth. Initial shoot length was consistently a significant predictor of seedling growth and survival, while number of first-order lateral roots (FOLR) and root collar diameter (RCD) were not under closed canopy. Based on the results from this study, underplanting shortly before timber harvesting is not recommended, but, when planning to wait at least one growing season to harvest after underplanting, planting larger seedlings will improve survival in closed-canopy forest.