Crown architecture of Populus spp. is differentially modified by free-air CO2 enrichment (POPFACE)

Authors

  • B. Gielen,

    Corresponding author
    1. University of Antwerp, UIA, Department of Biology, Research Group of Plant and Vegetation Ecology, Universiteitsplein 1, B-2610 Antwerpen (Wilrijk), Belgium;
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  • C. Calfapietra,

    1. Universita degli Studi della Tuscia, Department of Forest Environment and Resources (DISAFRI), Via San Camillo de Lellis, I-01100 Viterbo, Italy;
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  • A. Claus,

    1. University of Antwerp, UIA, Department of Biology, Research Group of Plant and Vegetation Ecology, Universiteitsplein 1, B-2610 Antwerpen (Wilrijk), Belgium;
    2. Present address: Institute for Vegetables and Ornamental Plants, Theodor-Echtermeyer-Weg 1, D-14989 Grossbeeren (Berlin), Germany
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  • M. Sabatti,

    1. Universita degli Studi della Tuscia, Department of Forest Environment and Resources (DISAFRI), Via San Camillo de Lellis, I-01100 Viterbo, Italy;
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  • R. Ceulemans

    1. University of Antwerp, UIA, Department of Biology, Research Group of Plant and Vegetation Ecology, Universiteitsplein 1, B-2610 Antwerpen (Wilrijk), Belgium;
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Author for correspondence: B. Gielen Tel: +32 3820 22 89 Fax: +32 3820 22 71 Email: bgielen@uia.ua.ac.be

Summary

  •  Although canopy architecture is a prime determinant of forest functioning and productivity, it has received little attention when examining forest responses to rising atmospheric CO2 concentrations. In this study different characteristics of crown architecture of two Populus species and one hybrid were investigated within a high-density poplar plantation. A free-air CO2 enrichment (FACE) facility was used to mimic future elevated CO2 concentrations.
  •  Canopy depth and branching patterns were studied, and detailed branch characteristics such as branch dimension, inclination, and internodal length were assessed for the three poplar species in the FACE and control treatments.
  •  Effects of elevated CO2 were restricted to a significantly increased canopy depth and longer internodal lengths after two years of CO2 enrichment. Additionally, branch dimensions and sylleptic branch numbers were increased by FACE, but responses were variable among growing seasons and species. However, FACE did not affect branch angles of origin and termination.
  •  Crown architecture was modified mainly through a growth stimulation in response to FACE. Nevertheless, important differences among species were observed which may influence future CO2 responses when competition will become more important.

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