© 2005 Heron Publishing—Victoria, Canada
Leaf photosynthetic traits of 14 tropical rain forest species in relation to leaf nitrogen concentration and shade tolerance
Sabrina Coste (1), Jean-Christophe Roggy (1, 2), Pascal Imbert (1), Céline Born (1), Damien Bonal (1) and Erwin Dreyer (3)
1. Unité Mixte de Recherche CIRAD-ENGREF-INRA-CNRS Écologie des Forêts de Guyane, Campus agronomique de Kourou, 97387 Kourou,
French Guiana / 2. Corresponding author (roggy.j@cirad.fr) / 3. UMR Écologie et Écophysiologie Forestières, INRA-UHP, 54280 Champenoux, France / Received September 24, 2004; accepted January 21, 2005; published online July 4, 2005
Summary
Variability of leaf traits related to photosynthesis was assessed in seedlings from 14 tree species growing in the tropical
rain forest of French Guiana. Leaf photosynthetic capacity (maximum rate of carboxylation and maximum rate of electron transport)
was estimated by fitting a biochemical model of photosynthesis to response curves of net CO2 assimilation rate versus intercellular CO2 mole fraction. Leaf morphology described by leaf mass per unit leaf area (LMA), density and thickness, as well as area- and
mass-based nitrogen (N) and carbon (C) concentrations, were recorded on the same leaves. Large interspecific variability was
detected in photosynthetic capacity as well as in leaf structure and leaf N and C concentrations. No correlation was found
between leaf thickness and density. The correlations between area- and mass-based leaf N concentration and photosynthetic
capacity were poor. Conversely, the species differed greatly in relative N allocation to carboxylation and bioenergetics.
Principal component analysis (PCA) revealed that, of the recorded traits, only the computed fraction of total leaf N invested
in photosynthesis was tightly correlated to photosynthetic capacity. We also used PCA to test to what extent species with
similar shade tolerances displayed converging leaf traits related to photosynthesis. No clear-cut ranking could be detected
among the shade-tolerant groups, as confirmed by a one-way ANOVA. We conclude that the large interspecific diversity in photosynthetic
capacity was mostly explained by differences in the relative allocation of N to photosynthesis and not by leaf N concentration,
and that leaf traits related to photosynthetic capacity did not discriminate shade-tolerance ranking of these tropical tree
species.
Keywords:
functional diversity, leaf carbon, leaf nitrogen, nitrogen-use efficiency, photosynthetic capacity, tropical rain forest.
