Watershed-scale vegetation, water quantity, and water quality responses to wildfire in the southern Appalachian mountain region, United States

Peter V. Caldwell, Katherine J. Elliott, Ning Liu, James M. Vose, David R. Zietlow, Jennifer D. Knoepp

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1 Scopus citations

Abstract

Wildfires are landscape scale disturbances that can significantly affect hydrologic processes such as runoff generation and sediment and nutrient transport to streams. In Fall 2016, multiple large drought-related wildfires burned forests across the southern Appalachian Mountains. Immediately after the fires, we identified and instrumented eight 28.4–344 ha watersheds (four burned and four unburned) to measure vegetation, soil, water quantity, and water quality responses over the following two years. Within burned watersheds, plots varied in burn severity with up to 100% tree mortality and soil O-horizon loss. Watershed scale high burn severity extent ranged from 5% to 65% of total watershed area. Water quantity and quality responses among burned watersheds were closely related to the high burn severity extent. Total water yield (Q) was up to 39% greater in burned watersheds than unburned reference watersheds. Total suspended solids (TSS) concentration during storm events were up to 168 times greater in samples collected from the most severely burned watershed than from a corresponding unburned reference watershed, suggesting that there was elevated risk of localized erosion and sedimentation of streams. NO3-N concentration, export, and concentration dependence on streamflow were greater in burned watersheds and increased with increasing high burn severity extent. Mean NO3-N concentration in the most severely burned watershed increased from 0.087 mg L−1 in the first year to 0.363 mg L−1 (+317%) in the second year. These results suggest that the 2016 wildfires degraded forest condition, increased Q, and had negative effects on water quality particularly during storm events.

Original languageEnglish (US)
Pages (from-to)5188-5209
Number of pages22
JournalHydrological Processes
Volume34
Issue number26
DOIs
StatePublished - Dec 2020

Bibliographical note

Funding Information:
We thank Katie Bower, Patsy Clinton, Andrew Danner, Jason Love, Charles Marshall, Joel Scott, Dani Thornton, and Brandon Welch for assistance in field sampling; and Cindi Brown, Kyle Coleman, Sheila Gregory, and Carol Harper for chemical analyses. We also thank Adam Coates, Dennis Hallema, Kevin Bladon, and two anonymous reviewers for their insightful comments on previous versions of this manuscript, and Paul Bolstad for consultation on initial study design. This research was supported by Coweeta Hydrologic Laboratory, Southern Research Station; Nantahala Ranger District and Southern Region 8; Water Resources Program Washington Office, USDA Forest Service; the National Science Foundation (NSF), Long‐Term Ecological Research (LTER) program (award #DEB‐0823293); the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Program, Agro‐ecosystem Management (award #2017‐67019‐26544); and The Nature Conservancy. Any opinions, findings, conclusions or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the USDA or the NSF.

Funding Information:
National Institute of Food and Agriculture, Grant/Award Number: 2017‐67019‐26544; National Science Foundation, Long‐term Ecological Research Program, Grant/Award Number: DEB‐0823293 Funding information

Funding Information:
We thank Katie Bower, Patsy Clinton, Andrew Danner, Jason Love, Charles Marshall, Joel Scott, Dani Thornton, and Brandon Welch for assistance in field sampling; and Cindi Brown, Kyle Coleman, Sheila Gregory, and Carol Harper for chemical analyses. We also thank Adam Coates, Dennis Hallema, Kevin Bladon, and two anonymous reviewers for their insightful comments on previous versions of this manuscript, and Paul Bolstad for consultation on initial study design. This research was supported by Coweeta Hydrologic Laboratory, Southern Research Station; Nantahala Ranger District and Southern Region 8; Water Resources Program Washington Office, USDA Forest Service; the National Science Foundation (NSF), Long-Term Ecological Research (LTER) program (award #DEB-0823293); the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Program, Agro-ecosystem Management (award #2017-67019-26544); and The Nature Conservancy. Any opinions, findings, conclusions or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the USDA or the NSF.

Keywords

  • nitrate
  • sediment
  • southern Appalachians
  • water quality
  • water yield
  • wildfire

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