Are competitive interactions influenced by spatial nutrient heterogeneity and root foraging behavior?

Authors

  • Kristin M. Bliss,

    1. Department of Biology, Virginia Tech, Blacksburg, VA 24061 USA;
    2. Present address: Biology Department, Randolf-Macon Women’s College, Lynchburg, VA 24503, USA
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  • Robert H. Jones,

    Corresponding author
    1. Department of Biology, Virginia Tech, Blacksburg, VA 24061 USA;
      Author for correspondence: Robert H. Jones Tel: +1 540 231 9514 Fax: +1 540 231 9307 Email: rhjones@vt.edu
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  • Robert J. Mitchell,

    1. Joseph W. Jones Ecological Research Center, Route 2, Box 2324, Newton, GA 31770, USA;
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  • Paul P. Mou

    1. Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, USA;
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Author for correspondence: Robert H. Jones Tel: +1 540 231 9514 Fax: +1 540 231 9307 Email: rhjones@vt.edu

Summary

  •  Nutrient heterogeneity, root foraging and competitive interactions were investigated for six species native to south-eastern USA.
  •  Monocultures, two- and six-species garden plots were fertilized to create spatially homogeneous or heterogeneous nutrient conditions. After 3.5 months, root proliferation in rich patches (precision), mean above-ground biomass per plant (scale) and influence of nutrient treatment on total plot biomass (sensitivity) in monocultures were measured. Competition (above-ground biomass) was assessed in two- and six-species plots.
  •  In monoculture plots, two species were relatively precise foragers, but no species showed significant sensitivity to nutrient treatment. Correlations between precision, scale and sensitivity were weak (−0.40 < r < 0.17), which contrasts with previous work showing a scale-precision trade-off. In two-species plots, competition was influenced by soil heterogeneity in two of six cases tested (anova, P < 0.05), and precise foragers grew larger in heterogeneous than in homogeneous conditions. In six-species plots, nutrient treatment had no influence on growth or competition.
  •  In our study system, heterogeneity effects on competition are context specific, generally weak and potentially mediated by the degree of root foraging precision.

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