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Changes in a tropical forest support metabolic zero-sum dynamics

Authors

  • S. K. Morgan Ernest,

    Corresponding author
    1. Department of Biology and the Ecology Center, Utah State University, Logan, UT 84322, USA
      *E-mail: morgane@biology.usu.edu
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  • Ethan P. White,

    1. Department of Biology and the Ecology Center, Utah State University, Logan, UT 84322, USA
    2. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA
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  • James H. Brown

    1. National Center for Ecological Analysis and Synthesis, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA
    2. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
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*E-mail: morgane@biology.usu.edu

Abstract

Major shifts in many ecosystem-level properties of tropical forests have been observed, but the processes driving these changes are poorly understood. The forest on Barro Colorado Island (BCI) exhibited a 20% decrease in the number of trees and a 10% increase in average diameter. Using a metabolism-based zero-sum framework, we show that increases in per capita resource use at BCI, caused by increased tree size and increased temperature, compensated for the observed declines in abundance. This trade-off between abundance and average resource use resulted in no net change in the rate resources are fluxed by the forest. Observed changes in the forest are not consistent with other hypotheses, including changes in overall resource availability and existing self-thinning models. The framework successfully predicts interrelated changes in size, abundance and temperature, indicating its utility for understanding changes in the structure and dynamics of ecosystems.

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