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This article in JEQ

  1. Vol. 37 No. 4, p. 1419-1431
     
    Received: July 6, 2007
    Published: July, 2008


    * Corresponding author(s): kelliott@fs.fed.us
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doi:10.2134/jeq2007.0358

Simulated Effects of Sulfur Deposition on Nutrient Cycling in Class I Wilderness Areas

  1. Katherine J. Elliott *a,
  2. James M. Vosea,
  3. Jennifer D. Knoeppa,
  4. Dale W. Johnsonb,
  5. Wayne T. Swanka and
  6. William Jacksonc
  1. a Coweeta Hydrologic Lab., Southern Research Stn., USDA Forest Service, Otto, NC 28763
    b Dep. of Environmental and Resource Sciences, Univ. of Nevada, Reno, NV 89512
    c Air Resources Program, Region 8, USDA Forest Service, Asheville, NC 28804

Abstract

We predicted the effects of sulfate (SO4) deposition on wilderness areas designated as Class I air quality areas in western North Carolina using a nutrient cycling model (NuCM). We used three S deposition simulations: current, 50% decrease, and 100% increase. We measured vegetation, forest floor, and root biomass and collected soil, soil solution, and stream water samples for chemical analyses. We used the closest climate stations and atmospheric deposition stations to parameterize NuCM. The areas were: Joyce Kilmer (JK), Shining Rock (SR), and Linville Gorge (LG). They differ in soil acidity and nutrients, and soil solution and stream chemistry. Shining Rock and LG have lower soil solution base cation and higher acidic ion concentrations than JK. For SR and LG, the soil solution Ca/Al molar ratios are currently 0.3 in the rooting zone (A horizon), indicating Al toxicity. At SR, the simulated Ca/Al ratio increased to slightly above 1.5 after the 30-yr simulation regardless of S deposition reduction. At LG, Ca/Al ratios ranged from 1.6 to 2.4 toward the end of the simulation period, the 100% increase scenario had the lower value. Low Ca/Al ratios suggest that forests at SR and LG are significantly stressed under current conditions. Our results also suggest that SO4 retention is low, perhaps contributing to their high degree of acidification. Their soils are acidic, low in weatherable minerals, and even with large reductions in SO4 and associated acid deposition, it may take decades before these systems recover from depletion of exchangeable Ca, Mg, and K.

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Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America