Leaf traits and decomposition in tropical rainforests: revisiting some commonly held views and towards a new hypothesis

Authors

  • Stephan Hättenschwiler,

    1. Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, 1919, route de Mende, F-34293 Montpellier Cedex 5, France
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  • Sylvain Coq,

    1. Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, 1919, route de Mende, F-34293 Montpellier Cedex 5, France
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  • Sandra Barantal,

    1. Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, 1919, route de Mende, F-34293 Montpellier Cedex 5, France
    2. UMR Ecologie des Forêts de Guyane, INRA Campus Agronomique, BP 709, F-97387 Kourou Cedex, Guyane Française
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  • Ira Tanya Handa

    1. Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, 1919, route de Mende, F-34293 Montpellier Cedex 5, France
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Author for correspondence:
S. Hättenschwiler
Tel: +33 467 61 22 36
Email: stephan.hattenschwiler@cefe.cnrs.fr

Summary

Proper estimates of decomposition are essential for tropical forests, given their key role in the global carbon (C) cycle. However, the current paradigm for litter decomposition is insufficient to account for recent observations and may limit model predictions for highly diverse tropical ecosystems. In light of recent findings from a nutrient-poor Amazonian rainforest, we revisit the commonly held views that: litter traits are a mere legacy of live leaf traits; nitrogen (N) and lignin are the key litter traits controlling decomposition; and favourable climatic conditions result in rapid decomposition in tropical forests. Substantial interspecific variation in litter phosphorus (P) was found to be unrelated to variation in green leaves. Litter nutrients explained no variation in decomposition, which instead was controlled primarily by nonlignin litter C compounds at low concentrations with important soil fauna effects. Despite near-optimal climatic conditions, tropical litter decomposition proceeded more slowly than in a climatically less favourable temperate forest. We suggest that slow decomposition in the studied rainforest results from a syndrome of poor litter C quality beyond a simple lignin control, enforcing energy starvation of decomposers. We hypothesize that the litter trait syndrome in nutrient-poor tropical rainforests may have evolved to increase plant access to limiting nutrients via mycorrhizal associations.

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