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Competitive status influences tree-growth responses to elevated CO2 and O3 in aggrading aspen stands

  1. E. P. McDonald1,*,
  2. E. L. Kruger2,
  3. D. E. Riemenschneider1,
  4. J. G. Isebrands1

Article first published online: 13 DEC 2002

DOI: 10.1046/j.1365-2435.2002.00683.x

Issue

Functional Ecology

Functional Ecology

Volume 16, Issue 6, pages 792–801, December 2002

Additional Information

How to Cite

McDonald, E. P., Kruger, E. L., Riemenschneider, D. E. and Isebrands, J. G. (2002), Competitive status influences tree-growth responses to elevated CO2 and O3 in aggrading aspen stands. Functional Ecology, 16: 792–801. doi: 10.1046/j.1365-2435.2002.00683.x

Author Information

  1. 1

    USDA-Forest Service, Forestry Sciences Laboratory, 5985 Hwy K, Rhinelander, WI 54501, and

  2. 2

    Department of Forest Ecology and Management, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI 53706, USA

* † Author to whom correspondence should be addressed. E-mail: epmcdonald@fs.fed.us

Publication History

  1. Issue published online: 13 DEC 2002
  2. Article first published online: 13 DEC 2002
  3. Received 29 May 2002;accepted 5 June 2002

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Keywords:

  • Competitive interactions;
  • FACE;
  • global change;
  • Populus tremuloides

Summary

  • 1
    Competition effects on growth of individual trees were examined for 4 years in aggrading, mixed-clone stands of trembling aspen (Populus tremuloides Michx.) at the Aspen-FACE free-air CO2 and O3 enrichment facility in northern Wisconsin, USA. During each growing season stands received one of four combinations of atmospheric [CO2] (ambient vs∼56 Pa) and [O3] (ambient vs∼1·5 × ambient).
  • 2
    Non-destructive measurements of annual tree growth were compared within and among clones and treatments in relation to an index of competitive status based on the difference between a tree's height and that of its four nearest neighbours. Competitive status strongly influenced tree growth, and the positive growth response to elevated [CO2] was greater for competitively advantaged individuals than for disadvantaged individuals of most clones.
  • 3
    The magnitude of O3 effects on growth depended on clone and competitive status: for some clones, negative O3 effects were stronger with competitive advantage while others showed stronger O3 effects with competitive disadvantage. The interactive effects of CO2 and O3 differed among clones, with negative effects of O3 amplified or ameliorated by elevated CO2, depending on clone and competitive status.
  • 4
    Treatments modified competitive interactions by affecting the magnitude of growth differences among clones. These modifications did not alter clone rankings of competitive performance, but when CO2 and O3 were both elevated, the differences in competitive performance among clones decreased.
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