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Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado

Abrahams, Edward R. ; Kaste, James M. ; Ouimet, William ; Dethier, David P.

Earth surface processes and landforms, 2018-07, Vol.43 (9), p.2009-2021 [Periódico revisado por pares]

Bognor Regis: Wiley Subscription Services, Inc

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  • Título:
    Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado
  • Autor: Abrahams, Edward R. ; Kaste, James M. ; Ouimet, William ; Dethier, David P.
  • Assuntos: Aridity ; Caesium ; Caesium 137 ; Cesium ; Cesium isotopes ; Cesium radioisotopes ; Convective storms ; erosion ; Erosion mechanisms ; Erosion models ; Erosion rates ; Fallout ; Fires ; Flooding ; Geomorphology ; Inventories ; Inventory management ; Landscape ; Lead ; Lead isotopes ; Radioisotopes ; Radionuclide kinetics ; radionuclides ; Runoff ; Sediment ; Sediment transport ; Sediments ; Slope ; Slopes ; Soil ; Soil analysis ; Soil erosion ; Soil moisture ; Soil profiles ; Soil properties ; Storms ; Surface runoff ; wildfire ; Wildfires
  • É parte de: Earth surface processes and landforms, 2018-07, Vol.43 (9), p.2009-2021
  • Descrição: Infrequent, high‐magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar‐ and equatorial‐facing burned slopes and on a polar‐facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil inventories are sensitive to erosion by surface runoff. The polar‐facing burned slope had significantly lower cesium‐137 (137Cs) and lead‐210 (210Pb) inventories (p < 0.05) than either the polar‐facing unburned slope or equatorial‐facing burned slope. Local slope magnitude does not appear to control the erosional response to wildfire, as relatively gently sloping (~20%) polar‐facing positions were severely eroded in the most intensively burned area. Field evidence and soil profile analyses indicate up to 4 cm of local soil erosion on the polar‐facing burned slope, but radionuclide mass balance indicates that much of this was trapped nearby. Using a 137Cs‐based erosion model, we find that the burned polar‐facing slope had a net mean sediment loss of 2 mm (~1 kg m−2) over a one to three year period, which is one to two orders of magnitude higher than longer‐term erosion rates reported for this region. In this part of the Colorado Front Range, strong hillslope asymmetry controls soil moisture and vegetation; polar‐facing slopes support significantly denser pine and fir stands, which fuels more intense wildfires. We conclude that polar‐facing slopes experience the most severe surface erosion following wildfires in this region, indicating that landscape‐scale aridity can control the geomorphic response of hillslopes to wildfires. Copyright © 2018 John Wiley & Sons, Ltd. We measure soil erosion in a fire‐impacted section of Fourmile Canyon, Colorado and find that sediment transport rates are higher on the steeper, polar‐facing burned hillslope in comparison with the drier south‐facing burned slopes. Local slope magnitude does not appear to control the erosional response to wildfire, but rather landscape‐scale aridity controls vegetation density and thus burn intensity. Given the current fire frequency, we calculate an erosion rate of approximately 0.01–0.02 mm yr−1 on north‐facing burned slopes from this process.
  • Editor: Bognor Regis: Wiley Subscription Services, Inc
  • Idioma: Inglês
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