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Journal of Environmental Quality Abstract - Landscape and Watershed Processes

Wildfire Effects on Soil Nutrients and Leaching in a Tahoe Basin Watershed


This article in JEQ

  1. Vol. 35 No. 2, p. 479-489
    Received: May 2, 2005

    * Corresponding author(s): dwj@cabnr.unr.edu
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  1. J. D. Murphya,
  2. D. W. Johnson *a,
  3. W. W. Millera,
  4. R. F. Walkera,
  5. E. F. Carrolla and
  6. R. R. Blankb
  1. a Natural Resources and Environmental Science, University of Nevada, Reno, NV 89557
    b USDA Agricultural Research Service, 920 Valley Road, Reno, NV 89512


A wildfire burned through a previously sampled research site, allowing pre- and post-burn measurements of the forest floor, soils, and soil leaching near Lake Tahoe, Nevada. Fire and post-fire erosion caused large and statistically significant (P ≤ 0.05) losses of C, N, P, S, Ca, and Mg from the forest floor. There were no statistically significant effects on mineral soils aside from a decrease in total N in the surface (A11) horizon, an increase in pH in the A11 horizon, and increases in water-extractable SO4 2− in the A11 and A12 horizons. Burning caused consistent but nonsignificant increases in exchangeable Ca2+ in most horizons, but no consistent or statistically significant effects on exchangeable K+ or Mg2+, or on Bray-, bicarbonate-, or water-extractable P concentrations. Before the burn, there were no significant differences in leaching, but during the first winter after the fire, soil solution concentrations of NH4 +, NO3 , ortho-P, and (especially) SO4 2− were elevated in the burned area, and resin lysimeters showed significant increases in the leaching of NH4 + and mineral N. The leaching losses of mineral N were much smaller than the losses from the forest floor and A11 horizons, however. We conclude that the major short-term effects of wildfire were on leaching whereas the major long-term effect was the loss of N from the forest floor and soil during the fire.

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