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Journal of Environmental Quality Abstract - Landscape and Watershed Processes

The Effects of Throughfall Manipulation on Soil Leaching in a Deciduous Forest


This article in JEQ

  1. Vol. 31 No. 1, p. 204-216
    Received: Feb 19, 2001

    * Corresponding author(s): dwj@unr.edu
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  1. D.W. Johnson *a,
  2. P.J. Hansonb and
  3. D.E. Toddb
  1. a Environmental and Resource Sciences, Fleischmann Agriculture Bldg/370, Univ. of Nevada, Reno, NV 89557
    b Environmental Sciences Division, Oak Ridge National Lab., P.O. Box 2008, Building 1059, Oak Ridge, TN 37831-6422


The effects of changing precipitation on soil leaching in a deciduous forest were examined by experimentally manipulating throughfall fluxes in the field. In addition to an ambient treatment (AMB), throughfall fluxes were reduced by 33% (DRY treatment) and increased by 33% (WET treatment) using a system of rain gutters and sprinklers on Walker Branch Watershed, Tennessee. Soil leaching was measured with resin lysimeters in the O horizons and with ceramic cup lysimeters in the E (25 cm) and Bt (70 cm) horizons. Large and statistically significant treatment effects on N fluxes were found in the O horizons (lower N fluxes in the DRY and higher N fluxes in the WET treatment). Together with the greater O horizon N content observed in the DRY treatment, this suggested that N was being immobilized at a greater rate in the DRY treatment than in the AMB or WET treatments. No statistically significant treatment effects on soil solution were found in the E horizons with the exception of (Ca2+ + Mg2+) to K+ ratio. Statistically significant treatment effects on electrical conductivity (EC), pH, Ca2+, Mg2+, K+, Na+, SO2− 4, and Cl were found in the Bt horizons due to differences between the DRY and other treatments. Despite this, calculated fluxes of Ca2+, Mg2+, K+, Na+, SO2− 4, and Cl were lowest in the DRY treatment. These results suggest that lower precipitation will cause temporary N immobilization in litter and long-term enrichment in soil base cations whereas increased precipitation will cause long-term depletion of soil base cations.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:204–216.