Background: Many forests within the southern Appalachian region, USA, have experienced decades of fire exclusion, contributing to regeneration challenges for species such as oaks (Quercus spp. L.) and pines (Pinus spp. L.), and threatening the maintenance of oak-dominated forests in the future. While the use of prescribed fire as a forest management tool is increasing within this region, there remains a lack of information on the potential role of wildfire. A wildfire within the Daniel Boone National Forest, Kentucky, USA, provided an opportunity to investigate how wildfire affected forest vegetation response. Results: We examined the effects of fire severity, quantified using composite burn index (CBI), on basal area, stem density, and sapling recruitment for several key species. We also examined the effects of fire severity on understory species richness and illuminated the consequence of non-native species invasions following fire. Our results demonstrated a negative relationship between fire severity and basal area (stems ≥2 cm diameter at breast height; P ≤ 0.001), and a positive relationship with the recruitment of oak and pine saplings (both P ≤ 0.001), oak sapling density (P = 0.012), and non-woody understory species richness (P ≤ 0.001). We also found that increasing fire severity heightened likelihood of invasion by non-native species, specifically princess tree (Paulownia tomentosa [Thunb.] Siebold & Zucc. ex. Steud; P = 0.009) and Chinese silvergrass (Miscanthus sinensis Andersson; P = 0.028). Conclusions: Where it is feasible, public land managers may be able to generate a range of fire severity during future prescribed fires that approximate some characters of wildfire. These fires, when implemented in southern Appalachian upland forests, may help recruit oaks and pines and boost their potential as future canopy dominants. However, the increased occurrence of non-native invasive species invasion following fire conveys the importance of targeted and timely eradication treatments before new populations of non-native species may become established or reproduce, contradicting the ecological benefits of fire.

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The contemporary decline of open woodlands in the eastern United States has prompted land managers to implement management prescriptions that encourage landscape and habitat diversity, often using mechanical thinning and prescribed fire as tools to alter stand structure. To increase habitat diversity and restore natural processes, a long-term oak woodland restoration project was planned for two upland hardwood stands in the Daniel Boone National Forest, Kentucky, United States. As an initial phase of restoration, we examined the effects of midstory mastication on stand structure, understory vegetation response, and fuels. The mastication treatment reduced stem density and basal area of trees ≤7.9 in. (20.1 cm) dbh by 69 percent and 47 percent, respectively, encouraged vigorous stump/root sprouting, and increased ground cover of forbs (204 percent) and native graminoids (253 percent) the first year on treated plots. Additionally, mastication created a variable cover of woody mulch on the forest floor and increased 1-h and 100-h time-lag fuels compared with controls. In year 2, Microstegium vimineum (invasive grass) cover increased by 700 percent on treated plots. This study imparts novel information on the mastication of upland hardwoods to benefit land managers in directing future treatments to shape desired stand structures and compositions, and increase landscape heterogeneity.

In the eastern deciduous forest region, open oak woodlands once occupied significant areas that are now closed-canopy forests, negatively affecting wildlife habitat and biodiversity. We superimposed midstory mastication and prescribed fire treatments onto sites with ice storm damage, subsequently subjected to sanitation thinning for management restoration. Mastication reduced stem density and basal area, created a variable cover of masticated material, and increased cover of forbs, graminoids, and tree regeneration. Prescribed fire was implemented two years after mastication treatment. We examined fuel changes and whether masticated fuels altered fire severity. Masticated duff depth decreased significantly two years after treatment; no change occurred on nonmasticated treatments. Masticated 1-hour fuels decreased 80% compared to 35% in nonmasticated treatments and masticated 10 h fuels decreased 45% compared to 9.6% in treatments without mastication. Prescribed fire reduced 1, 10, and 100 h fuels on the burn only treatment, and 10 h fuels on the mastication/burn treatment. Burn severity, measured by composite burn index, did not differ between treatments, nor did we measure significant effects of mastication on fire temperature or char height. Fire had no significant effect on stand structure but should be reexamined in three to five years. Repeated burning at three to five y intervals may also be beneficial. Study implications: This study examined the effects of mastication and prescribed fire on upland oak restoration. Findings suggest a single prescribed fire after mastication may not create stand structure reflective of oak woodland restoration priorities. Nonetheless, it will be important to examine fire effects several years later. Additional applications of prescribed fire may be effective in maintaining the stand structure initially achieved through ice storm disturbance, harvest, and mastication. Continued research could gauge the intensity and frequency of prescribed fire treatments needed to retain desired woodland stand structure and develop complex and diverse herbaceous understories characteristic of oak woodlands.