Leaf growth dynamics of two congener gymnosperm tree species reflect the heterogeneity of light intensities given in their natural ecological niche

Authors

  • I-LING LAI,

    1. Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei 106, Taiwan
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  • HANNO SCHARR,

    1. Institute of Chemistry and Dynamics of the Geosphere ICG-III: Phytosphere, Research Center Juelich GmbH, 52425 Juelich, Germany
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  • ANDRES CHAVARRIA-KRAUSER,

    1. Institute of Chemistry and Dynamics of the Geosphere ICG-III: Phytosphere, Research Center Juelich GmbH, 52425 Juelich, Germany
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  • RALF KÜSTERS,

    1. Institute of Chemistry and Dynamics of the Geosphere ICG-III: Phytosphere, Research Center Juelich GmbH, 52425 Juelich, Germany
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  • JIUNN-TZONG WU,

    1. Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei 106, Taiwan
    2. Research Center for Biodiversity and Institute of Botany, Academia Sinica, Taipei 115, Taiwan
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  • CHANG-HUNG CHOU,

    1. Department of Tropical Agriculture & International Cooperation, National Pingtung University of Science and Technology, Pingtung 912 Taiwan
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  • ULRICH SCHURR,

    1. Institute of Chemistry and Dynamics of the Geosphere ICG-III: Phytosphere, Research Center Juelich GmbH, 52425 Juelich, Germany
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  • ACHIM WALTER

    Corresponding author
    1. Institute of Chemistry and Dynamics of the Geosphere ICG-III: Phytosphere, Research Center Juelich GmbH, 52425 Juelich, Germany
      Achim Walter. Fax: +49 2461612492; e-mail: a.walter@fz-juelich.de
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Achim Walter. Fax: +49 2461612492; e-mail: a.walter@fz-juelich.de

ABSTRACT

Chamaecyparis obtusa var. formosana and Chamaecyparis formosensis are congener gymnosperm tree species native to Taiwan cloud forests; occupying different niches there. While the seedlings of C. formosensis occur predominantly under bright conditions in large forest gaps, seedlings of C. obtusa var. formosana are mainly found below the canopy of mature forests or in small gaps. It is well known that congener species occupying different niches typically differ in several ecophysiological and morphological traits, but the differences in growth dynamics of such species are still totally unclear, as the diurnal growth dynamics of gymnosperm leaves have not been investigated before. Modern methods of digital image sequence processing were used in this study to analyse the leaf growth dynamics of the two species. We found that both species show similar base–tip gradients and pronounced diurnal growth rhythms with maxima in the evening. Differences between the two species concerning their growth dynamics correlated closely with their ecological amplitudes and abundances. Chamaecyparis obtusa var. formosana grew faster than C. formosensis in low light intensity, typical for closed-canopy situations, and reacted quickly by increasing or decreasing growth rate when light intensity changed within a range typically found below small canopy gaps. In contrast to this, C. formosensis grew better in light intensities typical for open vegetation situations, but reacted slower towards changes of light intensity. Based on those results, the hypothesis can be developed that fluctuations of leaf growth dynamics reflect heterogeneities of the light environment within the niche occupied by a given species.

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