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This article in SSSAJ

  1. Vol. 65 No. 6, p. 1709-1716
    Received: Mar 18, 2001

    * Corresponding author(s): grundman@biomserv.univ-lyon1.fr
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Spatial Modeling of Nitrifier Microhabitats in Soil

  1. G. L. Grundmann *a,
  2. A. Dechesnea,
  3. F. Bartolib,
  4. J. P. Flandroisc,
  5. J. L. Chasséc and
  6. R. Kizunguc
  1. a Laboratoire d'Ecologie microbienne, U.M.R. C.N.R.S. 5557. UCB Lyon I, 43 Bd du 11 Novembre 1918. 69622 Villeurbanne, Cedex, France
    b Centre de Pédologie Biologique, UPR 6831 CNRS-Université Henri-Poincaré, Nancy I, 17 rue Notre Dame des Pauvres BP5, 54 501 Vandoeuvre-Les-Nancy
    c Laboratoire de Biométrie et Biologie Evolutive, U.M.R. C.N.R.S. 5558, UCB Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne, Cedex, France


Soil bacteria function in the three-dimensional space in heterogeneous soil complex and their activities depend in part on encountering substrates at the microbial scale. The bacterial density per gram of soil, which is generally measured, does not indicate if bacteria are all in the same location or spread throughout the soil complex. We characterized spatial distribution for how dispersed or aggregated nitrifiers (NH+ 4 and NO 2 oxidizers) were at a submillimeter scale. The spatial approach was based on the relationship, obtained experimentally, between the percentage of microsamples (50–500 μm diam.) harboring nitrifiers and the volume of the microsamples. The smallest sample size (50-μm diam.) was considered as an approximation of microhabitat. The simulated spatial pattern of NO 2 oxidizer microhabitats in soil were compared with experimental data. The simulated pattern of NO 2 oxidizer distribution suggested that microhabitats averaged seven NO 2 oxidizers and occurred in preferentially colonized patches that had about a 250-μm diam. These were randomly distributed and occupied 5.5% of the soil volume. They were functionally connected through microporosity and hence diffusion processes probably controlled the spatial distribution of nirifiers. The nitrifier spatial pattern enabled efficient nitrification because NH+ 4 and NO 2 oxidizers were near one another. The results showed the potential of our method to study spatial distribution of bacteria at the microhabitat scale.

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Copyright © 2001. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.65:1709–1716.