Leaf size and leaf display of thirty-eight tropical tree species |
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Authors: | Lourens Poorter Danaë M A Rozendaal |
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Institution: | (1) Forest Ecology and Forest Management Group, Center for Ecosystem Studies, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands;(2) Instituto Boliviano de Investigación Forestal, P.O. Box 6204, Santa Cruz, Bolivia;(3) Resource Ecology Group, Center for Ecosystem Studies, Wageningen University, Wageningen, The Netherlands;(4) Section of Plant Ecology and Biodiversity, Faculty of Science, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands |
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Abstract: | Trees forage for light through optimal leaf display. Effective leaf display is determined by metamer traits (i.e., the internode,
petiole, and corresponding leaf), and thus these traits strongly co-determine carbon gain and as a result competitive advantage
in a light-limited environment. We examined 11 metamer traits of sun and shade trees of 38 coexisting moist forest tree species
and determined the relative strengths of intra- and interspecific variation. Species-specific metamer traits were related
to two variables that represent important life history variation; the regeneration light requirements and average leaf size
of the species. Metamer traits varied strongly across species and, in contrast to our expectation, showed only modest changes
in response to light. Intra- and interspecific responses to light were only congruent for a third of the traits evaluated.
Four traits, amongst which leaf size, specific leaf area (SLA), and leaf area ratio at the metamer level (LAR) showed even
opposite intra- and interspecific responses to light. Strikingly, these are classic traits that are thought to be of paramount
importance for plant performance but that have completely different consequences within and across species. Sun trees of a
given species had small leaves to reduce the heat load, but light-demanding species had large leaves compared to shade-tolerants,
probably to outcompete their neighbors. Shade trees of a given species had a high SLA and LAR to capture more light in a light-limited
environment, whereas shade-tolerant species have well-protected leaves with a low SLA compared to light-demanding species,
probably to deter herbivores and enhance leaf lifespan. There was a leaf-size-mediated trade-off between biomechanical and
hydraulic safety, and the efficiency with which species can space their leaves and forage for light. Unexpectedly, metamer
traits were more closely linked to leaf size than to regeneration light requirements, probably because leaf-size-related biomechanical
and vascular constraints limit the trait combinations that are physically possible. This suggests that the leaf size spectrum
overrules more subtle variation caused by the leaf economics spectrum, and that leaf size represents a more important strategy
axis than previously thought.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Allocation Foraging Internode Leaf size Light Shade tolerance |
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