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This article in SSSAJ

  1. Vol. 51 No. 6, p. 1634-1640
    Received: Nov 5, 1985

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Impacts of Acid Atmospheric Deposition on Woodland Soils in the Netherlands: II. Nitrogen Transformations1

  1. N. van Breemen,
  2. J. Mulder and
  3. J. J. M. van Grinsven2



Inorganic N budgets were estimated for four oak-birch (Quercus robur L.-Betula pendula L.) woodland soils in the Netherlands, that receive high inputs (40–60 kg ha−1 yr−1) of atmospheric N, mainly as (NH4)2SO4-. Budgets were based on measured inputs in through-fall water, measured soil solution concentrations, and simulated soil-water fluxes. Substantial nitrification occurred in both highly acidic (pH 3–4) and calcareous (pH 6.5–7.5) soils. The acidity formed during N transformations (3–9 kmolc ha−1 yr−1) accounted for a major part of all soil acidification taking place. Extreme soil acidification due to nitrification (4–14 kmolc ha−1 yr−1) in the 10-cm surface soil in three of the four plots was partly alleviated at greater depth by removal of NO-3. Presumably, most of this NO-3 was removed by plants and microorganisms and, perhaps, in part by denitrification. In two of the four soils, leaching of inorganic NO-3 exceeded atmospheric throughfall input. This trend indicates that N inputs were still higher, e.g., due to direct assimilation of atmospheric NH3 by tree leaves, or that the pool of soil N decreased by mineralization in excess of uptake. In one of the four soils, most of the atmospheric N2 was assimilated and soil acidification due to N transformations was relatively small. The differences in N budgets and associated soil acidification may be related to (i) consistent differences in N input over many years, and (ii) differences in accumulation of N in biomass. Variation in these two factors may be responsible for differences in the degree to which the ecosystems are now “saturated” with N.

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