dNBR imagery and xeric pine-oak forest stand characteristics for fires of different severity in Great Smoky Mountains National Park

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Scott A. Abla (Creator)
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Laura DeWald

Abstract: Fire suppression has changed forest structure and composition on xeric sites in the southern Appalachians from open, pine-oak dominated stands to closed canopy, mixed hardwood stands. Improved understanding of fire-related tools and ecological responses will improve effectiveness of fire management aimed at restoring pre-fire suppression forest communities on these xeric sites. Although occurrence of fire is known to be related to ecosystem functioning, vegetation responses to multi-severity fires are not as well understood in the southern Appalachians. Additionally, the relationship between satellite imagery and ground-based methods for designating burn severity (post-fire term describing fire severity) are not established for the Great Smoky Mountains National Park (GSMNP). The purpose of my study was to (1) determine if burn severity designations were consistent between satellite imagery and ground-based methods, and (2) evaluate vegetation responses to different burn severities on xeric sites dominated by pine (Pinus) and oak (Quercus) species in the GSMNP. Plots were randomly located using satellite-based (dNBR) burn severity maps. For part (1) of my study these sites were ground-truthed using the FIREMON Composite Burn Index (CBI). Initial scatter plots between CBI and dNBR indicated a saturated growth relationship and square-root transformed dNBR data were overall strongly correlated to ground-based ratings (CBI) for 169 total plots (p<0.001, R2=0.90). Strong relationships were found between CBI and dNBR across different xeric forest types and time since burn categories. For part (2) of my study, variables related to stand regeneration were measured at the ground, mid-story, and overstory layers across different burn severities for 48 plots. Differences in post-fire forest structure and composition across burn severity classifications were tested using analyses of variance and relationships between stand variables were evaluated using linear regression. Results showed overstory mortality was significantly higher in moderate and high severity sites versus low severity and no burn sites. Stand density and basal area were lowest in high severity sites and litter layer depth decreased significantly in higher severity fires. Pine regeneration did not vary across burn severities and oak regeneration was highest in moderate severity sites. Mixed mesophytic regeneration was highest in sites absent of fire. Desired pine and oak regeneration was greatest in moderate burn severity sites. Changes in species composition following fire may have been caused by greater amount of exposed mineral soil, increased light penetration to forest floor, and reduced mid-story stem densities. Overall results from both studies show that (1) burn severity can be predicted from satellite imagery and (2) different burn severities are associated with different forest structure and composition related to pine and oak regeneration on xeric sites in GSMNP.

Additional Information

Language: English
Date: 2014
CBI, dNBR, fire, GSMNP, severity, yellow pine
Forest fires -- Environmental aspects -- Great Smoky Mountains National Park (N.C. and Tenn.)
Forest biodiversity -- Effect of fires on -- Great Smoky Mountains National Park (N.C. and Tenn.)
Xeric ecology -- Great Smoky Mountains National Park (N.C. and Tenn.)

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