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Soil Science Society of America Journal Abstract -

Three Decades of Observed Soil Acidification in the Calhoun Experimental Forest: Has Acid Rain Made a Difference?


This article in SSSAJ

  1. Vol. 62 No. 5, p. 1428-1439
    Received: July 28, 1997

    * Corresponding author(s): dmarke@smokey.forestry.uga.edu
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  1. Daniel Markewitz ,
  2. Daniel D. Richter,
  3. H. Lee Allen and
  4. J. Byron Urrego
  1. Nicholas School of the Environment, Duke Univ., Durham, NC 27707
    Forest Nutrition Cooperative, Dep. of Forestry, North Carolina State Univ., Raleigh, NC 27695
    Smurfit - Carton de Colombia, Investigacion Forestal Calle 9, Calli, Colombia



Three decades of repeated soil sampling from eight permanent plots at the Calhoun Experimental Forest in South Carolina allowed us to estimate the rate of soil acidification, the chemical changes in the soil exchange complex, and the natural and anthropogenic sources of acidity contributing to these processes. During the first 34 yr of loblolly pine (Pinus taeda L.) forest growth, soil pH, (pH in 0.01 M CaCl2) decreased by 1 unit in the upper 0- to 15-cm of soils and by 0.4 and 0.3 units in the 15- to 35- and 35- to 60-cm layers, respectively. Throughout the 0- to 60-cm horizon, base cation depletion averaged 1.57 kmolc ha-1 yr-1 and effective and total acidity increased by 1.26 and 3.28 kmolc ha-1 yr-1, respectively. A forest H+ budget estimated for these decades indicated that 38% of soil acidification was due to acid deposition, while 62% of soil acidification was attributed to the internal functioning of the ecosystem. Soil samples archived during the three-decade experiment also document decreases in soil-adsorbed SO2-4, presumably in response to decreasing atmospheric inputs in recent years.

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