Watershed‐scale vegetation, water quantity, and water quality responses to wildfire in the southern Appalachian mountain region, United States. Issue 26 (23rd October 2020)

• Record Type: Journal Article
• Authors: Caldwell, Peter V.; Elliott, Katherine J.; Liu, Ning; Vose, James M.; Zietlow, David R.; Knoepp, Jennifer D.
• Is Part Of: Hydrological processes. Volume 34:Issue 26(2020)
• Page Start: 5188
• Page End: 5209
• Publication Date: 2020-10-23
• Subjects: nitrate -- sediment -- southern Appalachians -- water quality -- water yield -- wildfire; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.13922
• Languages: English
• ISSNs: 0885-6087

Abstract

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. Abstract : This study provides new information describing watershed‐scale vegetation, soil, water quantity, and water quality responses to severe wildfire in the humid deciduous forests of the eastern United States. While previous studies of low to moderate severity prescribed fires in the southern Appalachians showed negligible water quality effects, the results of this study suggest potential for elevated short‐term risk of high stormflows and water quality issues where a large proportion of a watershed is burned at high severity.