Considerations and Challenges for Oak-Pine Woodland Restoration in the Southern Appalachians

Author

• Armin Weise, Clemson UniversityFollow

Date of Award

8-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry and Environmental Conservation

Committee Chair/Advisor

Donald Hagan

Committee Member

Robert Baldwin

Committee Member

Kyle Barrett

Committee Member

Adam Coates

Abstract

Appalachian forests in the southeastern United States are composed of fire-adapted communities. These have historically been burned by native Americans and by lightning-ignited fires, causing widespread ignitions across the landscape for millennia that have shaped the forest and the species within it. Many of the more xeric oak-pine forest systems in the region were more akin to woodlands with open midstories, understocked canopies, and a diverse understory layer of herbaceous species and shrubs. With the decline of Native Americans due to disease and forced removal, fire across the landscape declined, a trend compounded by fire-suppression policies put forth by the United States government throughout the 20^th century. As a result, oak-pine woodlands lost much of their herbaceous layer, grew denser with shrubs and a cluttered midstory, and began to steadily shift their overall species composition from oak-pine and hickory dominance toward more mesophytic species such as red maple and yellow-poplar. The Green River Fire and Fire Surrogate Study in North Carolina was established in 2001 and has helped managers understand how densification and mesophication processes can be addressed. The study included four treatments: repeated prescribed fire, mechanical cutting of midstory trees and shrubs, a combination of these two treatments, and a control. Based on this study’s framework, this dissertation discusses several considerations and challenges at the heart of the increasing restoration effort of southern Appalachian woodlands. It aims to shine light on previously unknown patterns in how forests are responding to these treatments, how infrequent high-intensity disturbance events may influence these patterns, and how non-native invasive species are challenging the measures of success.

Chapter 1 investigated long-term overstory changes over 23 years, with a particular focus on the development of woodland structure and shifts in species composition. It tracked long-term patterns in overstory basal area, tree density and the mesophytic and xerophytic components. Unburned treatments consistently grew denser with increasing basal areas and mesophytic components. Mechanical cutting reduced midstory clutter and stalled some mesophication trends, which were otherwise advancing in the control, but it similarly continued to densify away from the historical woodland structure. The repeated application of fire facilitated a steady decline in forest density, more open midstories, and a decline of mesophytic overstory components while largely maintaining the overstory abundance of oak. In combination with mechanical cutting, repeated prescribed fire had a more drastic and accelerated progression towards reducing stand density and mesophytic components but also introduced greater variability in canopy density.

Chapter 2 analyzed the patterns of disturbance imposed by Hurricane Helene on the overstory composition through the downing of trees. As the hurricane toppled 5% of the overstory trees (and 8% of the basal area), primarily oak, with large-diameter fire-scarred trees being most susceptible. Midstory sourwoods were also disproportionately susceptible to being downed likely due to their diagonal growth. However, disparities in downed oak species, with red oaks (particularly scarlet oak) falling at higher relative rates than white oaks, led to a compositional shift in favor of longer-lived white and chestnut oaks. Although these patterns created more open overstories across treatments, this resulted in opportunities for shade-tolerant midstory species in the unburned treatments, accelerating the potential for mesophication. In the burned treatments, in contrast, the downing of trees contributed to the further development of favorable woodland conditions with reduced potential for advancing shade-tolerant midstory trees to negate those benefits.

Chapter 3 examined the infestation of Chinese silvergrass (Miscanthus sinensis), which has been progressing primarily in the burned treatments. Being a large, aggressive bunchgrass particularly well-adapted to frequent fire, it is known to trigger the grass-fire cycle in both its native and introduced ranges. As such the grass’ spread is facilitated by fire, increasing Miscanthus abundance, which eventually results in higher fire frequency and intensity. The repeated treatments of prescribed fire of this study facilitated Miscanthus invasion by reducing canopy cover and creating a seedbed ideal for its establishment in areas particularly prone to high-severity fire, especially when in proximity to source populations. Because the grass can disperse over long distances (up to 400 – 1000+ m) through small wind-dispersed seeds, eliminating potential nearby source populations could reduce its spread into prescribed fire units. This study recommends that managers closely survey the interior and surrounding areas of potential treatment units before and after the use prescribed fire. The study cautions that this invasive grass has the potential to undermine many of the successes discussed in the previous two chapters and calls for action to prevent its invasion before its threat becomes too difficult to manage.

These results demonstrate that the repeated application of prescribed fire can produce slow but enduring trends in reducing targeted mesophytic and shade-tolerant overstory species. In subsequent interaction with natural disturbances such as hurricanes, however, such treatments can result in favorable opening of the overstory paired with a shift in composition towards a greater dominance of desired oak species. Preceding the repeated application of fire with a one-time mechanical cutting of woody stem resulted in a faster reduction in targeted mesophytic and shade-tolerant species as well as the development of a woodland canopy. While it likewise benefited from the hurricane-induced disturbance, the resultant wide variation in canopy openness and other high fire-severity induced factors, this treatment sequence resulted in structural conditions making the forest more vulnerable by the invasion by the non-native invasive Miscanthus sinensis. Although the rapid development of favorable woodland characteristics has previously been favored by managers, the slower advancement of these conditions in combination with hurricane-induced disturbances may yield similar results, with less pressure from the non-native invasive Miscanthus sinensis, but will require a longer timeframe to measure success.

Recommended Citation

Weise, Armin, "Considerations and Challenges for Oak-Pine Woodland Restoration in the Southern Appalachians" (2026). All Dissertations. 4295.
https://open.clemson.edu/all_dissertations/4295

Author ORCID Identifier

0009-0004-5050-196X