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Large losses of inorganic nitrogen from tropical rainforests suggest a lack of nitrogen limitation

Authors

  • E. N. J. Brookshire,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
    2. Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USA
      E-mail: jbrookshire@montana.edu
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  • Stefan Gerber,

    1. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
    2. Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA
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  • Duncan N. L. Menge,

    1. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
    2. National Center for Ecological Analysis and Synthesis, Santa Barbara, CA, USA
    3. Department of Biology, Stanford University, Stanford, CA 94305, USA
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  • Lars O. Hedin

    1. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
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E-mail: jbrookshire@montana.edu

Abstract

Ecology Letters (2011) 14: 9–16

Abstract

Inorganic nitrogen losses from many unpolluted mature tropical forests are over an order of magnitude higher than losses from analogous temperate forests. This pattern could either reflect a lack of N limitation or accelerated plant–soil N cycling under tropical temperatures and moisture. We used a simple analytical framework of the N cycle and compared our predictions with data of N in stream waters of temperate and tropical rainforests. While the pattern could be explained by differences in N limitation, it could not be explained based on up-regulation of the internal N cycle without invoking the unlikely assumption that tropical plants are two to four times less efficient at taking up N than temperate plants. Our results contrast with the idea that a tropical climate promotes and sustains an up-regulated and leaky – but N-limited – internal N cycle. Instead, they are consistent with the notion that many tropical rainforests exist in a state of N saturation.

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