Abstract
Decades of fire exclusion in the Southern Appalachian Mountains led to fuel accumulation and conversion from open oak-pine woodlands to closed-canopy mesic forests dominated by shade-tolerant hardwoods and shrubs that often do not support a diverse understory. Southern Appalachian forest managers and scientists recognize this and are implementing silvicultural treatments such as prescribed burning, mechanical treatments or a combination of these to restore forest structure. In this study, conducted at the Southern Appalachian Fire and Fire Surrogate Study site in Green River Game Land, North Carolina, we assessed the effects of four fuel reduction methods: burned 4x (B), mechanical treatment 2x (M), mechanical treatment 2x + burned 4x (MB), and control (C) on the changes in understory vegetation guilds from pretreatment to post-treatment years (2001–2016). The MB treatment was most effective at meeting the restoration objectives, as it resulted in increases in oak (ΔMB = 23,400 stems/ha) and pine (ΔMB = 900 stems/ha) stem density, importance value - calculated as the sum of relative cover and frequency - for graminoids (ΔMB = 26.0), and density of oak stems >50 cm in height (ΔMB = 7133 stems/ha). The B and M treatments were generally less effective, but nonetheless met a subset of the restoration objectives. The B treatment reduced ericaceous shrub cover (ΔB = −1.2%) and increased oak stems 10–50 cm in height (ΔB = 10,017 stems/ha), while the M treatment resulted in only modest increases of mesic hardwoods, specifically for yellow-poplar (ΔM = 200 stems/ha) and blackgum (ΔM = 200 stems/ha) as compared with other treatments, but significantly increased mountain laurel and rhododendron cover (ΔM = 10.0%). Overall, these fire and fire surrogate treatments had some success in restoring understory structure, but our findings suggest a slow response in understory herbaceous vegetation.
Highlights
A continuum of ecological communities, from savannahs to woodlands to closed canopy forests, historically existed across the southern Appalachian region, and this landscape heterogeneity was reinforced by frequent fire
Absolute cover % of oaks significantly increased after mechanical and burning (MB) (∆ = 6.7% ± 5.2%) treatments which was statistically different from significant increases observed in the B (∆ = 3.3% ± 5.2%) treatments (p < 0.01, Figure 2b)
Changes in the density of oak stems 50 cm significantly increased after MB (∆ = 7133 ± 8271 stems/ha) treatments (p < 0.01, Figure 3)
Summary
A continuum of ecological communities, from savannahs to woodlands to closed canopy forests, historically existed across the southern Appalachian region, and this landscape heterogeneity was reinforced by frequent fire In these communities, frequent fires helped create conditions that supported the regeneration of fire-maintained vegetation, including many early successional herbaceous species [1]. Decades of fire exclusion have largely contributed to the loss of “open” communities, and a shift towards denser, more mesic forests [6,7] This ecological shift, often called “mesophication”, is the result of excess shade created by dense vegetation in areas that were previously open and dry, causing a cool, damp microclimatic effect in the understory [8]. These conditions support the encroachment of fire-sensitive vegetation, like eastern white pine (Pinus strobus L.), red maple (Acer rubrum L.), yellow-poplar (Liriodendron tulipifera L.), American beech (Fagus grandifolia Ehrh.), black birch (Betula lenta L.), blackgum (Nyssa sylvatica Marshall), and black cherry
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
