Directional changes in the species composition of a tropical forest

Authors

  • Kenneth J. Feeley,

    Corresponding author
    1. Department of Biological Sciences, Florida International University, Miami, Florida 33199 USA
    2. Fairchild Tropical Botanic Garden, Coral Gables, Florida 33156 USA
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  • Stuart J. Davies,

    1. Center for Tropical Forest Science, Smithsonian Tropical Research Institute and Arnold Arboretum, Harvard University, Cambridge, Massachusetts 02138 USA
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  • Rolando Perez,

    1. Center for Tropical Forest Science, Smithsonian Tropical Research Institute and Arnold Arboretum, Harvard University, Cambridge, Massachusetts 02138 USA
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  • Stephen P. Hubbell,

    1. Center for Tropical Forest Science, Smithsonian Tropical Research Institute and Arnold Arboretum, Harvard University, Cambridge, Massachusetts 02138 USA
    2. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California 90095 USA
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  • Robin B. Foster

    1. The Field Museum, Chicago, Illinois 60605 USA
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Abstract

Long-term studies have revealed that the structure and dynamics of many tropical forests are changing, but the causes and consequences of these changes remain debated. To learn more about the forces driving changes within tropical forests, we investigated shifts in tree species composition over the past 25 years within the 50-ha Forest Dynamics Plot on Barro Colorado Island (BCI), Panama, and examined how observed patterns relate to predictions of (1) random population fluctuations, (2) carbon fertilization, (3) succession from past disturbance, (4) recovery from an extreme El Niño drought at the start of the study period, and (5) long-term climate change. We found that there have been consistent and directional changes in the tree species composition. These shifts have led to increased relative representations of drought-tolerant species as determined by the species' occurrence both across a gradient of soil moisture within BCI and across a wider precipitation gradient from a dry forest near the Pacific coast of Panama to a wet forest near its Caribbean coast. These nonrandom changes cannot be explained by stochastic fluctuations or carbon fertilization. They may be the legacy of the El Niño drought, or alternatively, potentially reflect increased aridity due to long-term climate change. By investigating compositional changes, we increased not only our understanding of the ecology of tropical forests and their responses to large-scale disturbances, but also our ability to predict how future global change will impact some of the critical services provided by these important ecosystems.

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