Tissue-level leaf toughness, but not lamina thickness, predicts sapling leaf lifespan and shade tolerance of tropical tree species


  • Kaoru Kitajima,

    1. Department of Biology, University of Florida, Gainesville, FL 32611, USA
    2. Smithsonian Tropical Research Institute, Balboa, Panama
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  • Lourens Poorter

    1. Forest Ecology and Forest Management Group and Resource Ecology Group, Center for Ecosystem Studies, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands
    2. Instituto Boliviano de Investigación Forestal, PO Box 6204, Santa Cruz, Bolivia
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Author for correspondence:
Kaoru Kitajima
Tel: +1 352 3924234
Email: kitajima@ufl.edu


  • Leaf toughness is thought to enhance physical defense and leaf lifespan. Here, we evaluated the relative importance of tissue-level leaf traits vs lamina thickness, as well as their ontogenetic changes, for structure-level leaf toughness and regeneration ecology of 19 tropical tree species.
  • We measured the fracture toughness of the laminas and veins of sapling leaves with shearing tests, and used principal component analysis and structural equation modeling to evaluate the multivariate relationships among traits that contribute to leaf toughness and their links to ecological performance traits.
  • Tissue traits (density and fracture toughness of lamina and vein) were correlated positively with each other, but independent of lamina thickness. The tissue traits and lamina thickness contributed additively to the structure-level toughness (leaf mass per area and work-to-shear). Species with dense and tough leaves as saplings also had dense and tough leaves as seedlings and adults. The patterns of ontogenetic change in trait values differed between the seedling-to-sapling and sapling-to-adult transitions.
  • The fracture toughness and tissue density of laminas and veins, but not the lamina thickness, were correlated positively with leaf lifespan and sapling survival, and negatively with herbivory rate and sapling regeneration light requirements, indicating the importance of tissue-level leaf traits.