The development of oak stems of advance regeneration and stump sprout origin was studied during a two-year period following clearcutting and whole-tree removal in eight midslope stands in the Ridge and Valley Province of southwestern Virginia. Oak regeneration was also characterized in several older clearcuts. Height and diameter of oaks of stump sprout origin in the two-year-old stands was significantly greater than that of advance regeneration stems, and the difference in size among regeneration types appeared to persist into the oldest (17- and 28-year-old) stands sampled. Chestnut oak, which had been the dominant oak species in most pre-harvest stands, had higher density of advance regeneration stems, higher frequency of stump sprouting, and greater sprout production per stump than scarlet or black oak two years after harvesting. However, shoot growth of advance regeneration during the two-year period did not differ among oak species when initial stem site and vigor were accounted for taller stump sprouts in the two-year-old stands were associated with more productive sites (as indicated by site index, topographic variables, and vegetation composition), whereas biomass production per stump was less closely related to site quality. Height and diameter growth of oak advance regeneration during the two-year post-harvest period were significantly greater on sites of medium quality than OD sites of low quality. Density of well-established oak stems of advance regeneration origin two years after harvest was greatest in stands of site index 55-65 (base age 50), and fell off on sites of higher and lower quality. Models developed to predict two-year stump sprout production from characteristics of the parent tree generally explained less than 40 percent of the variation among stumps, while models describing growth of advance regeneration individuals from pre-harvest measurements accounted for as much as 82 percent of the variation. Regeneration in most of the two-year-old stands appeared adequate for restocking of oaks to at least their pre-harvest level, although stems will probably be widely spaced and mostly of stump sprout origin on both the poorest and the most productive sites. / Ph. D.

Canopy mortality. species abundance. and the species composition and origin of regeneration in mixed oak forests were studied following a 1900 ha man-caused early growing season wildfire in Shenandoah National Park. in the Blue Ridge Physiographic Province. Virginia. Pre-fire stands were dominated by chestnut. scarlet, and northern red oaks growing on medium quality sites (50 year upland oak site index 16-20 m). Permanent vegetation plots were established in four stands for each of high and low levels of fire intensity. and unburned stands. High-intensity fire killed 67% of the basal area and 81% of the trees, whereas low-intensity fire resulted in mortality of 8% of the basal area and 15% of the trees. The mean height of stem-bark char accounted for 91% and 95% of the variation in percent of the basal area and number of trees killed by fire, respectively. Logistic regression models were developed to predict the probability of fire-induced individual tree mortality (top-kill) as a function of DBH and height of stem-bark char for chestnut oak, scarlet and northern red oaks, pignut hickory, blackgum. and red maple. Blackgum and chestnut oak were the most fire resistant species studied. High-intensity fire resulted in the development of a new stand, whereas low-intensity fire resulted in thinning of the overstory and understory. Most species present in pre-fire stand reproduced via basal sprouts, chestnut oak sprouts were the most abundant stems taller than 1 m two growing seasons after high-intensity fire. Tree-of-heaven was the only species to regenerate by seed and able to match the height growth of oak basal sprouts. This research suggests that oaks are capable of replacing themselves on medium quality sites following wildfire-induced canopy removal in 55 to 60 year old stands. / Master of Science

Many existing Piedmont hardwood stands are composed of trees that are largely under 45 cm in diameter and contain a desirable oak component, as well as large amounts of undesirable red maple and sourwood. In stands under even-aged silviculture, season of harvest can be used as an effective management tool to favor different species compositions. If oak or other hardwood production is the management objective a dormant season harvest will result in increased sprout vigor of all oak as well as non-oak species. If pine conversion is the objective then a growing season harvest will reduce the vigor of all hardwood species and allow for easier competition control. The higher densities of all classes of regenerants on better sites indicates control will be more difficult. / Master of Science