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Relationship between herbivory and leaf traits in mangroves on Iriomote Island, southern Japan
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  • Yu Hirano,
  • Motoki Marui,
  • Shuhei Tachikake,
  • Taku Kato,
  • Nobuo Imai
Yu Hirano
Tokyo University of Agriculture
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Motoki Marui
Tokyo University of Agriculture
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Shuhei Tachikake
The University of Tokyo
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Taku Kato
Tokyo University of Agriculture
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Nobuo Imai
Tokyo University of Agriculture

Corresponding Author:[email protected]

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Abstract

Leaf herbivory potentially affects carbon (C) and nutrient cycling in forest ecosystems. It is especially critical to study the leaf herbivory rates in mangroves to understand the pattern of resource changes from the detrital pathway to the grazing pathway. However, determinants of leaf herbivory rates in mangroves are poorly understood. We examined the differences in leaf herbivory rates among leaf phenotypes (sun or shade leaves), leaf status (young or old leaves), and season (summer or winter) and investigated the relationships between the leaf herbivory rates and 12 leaf traits (including chemical, physiological, and physical/mechanical traits) in each of six communities from the seaward fringe to the inland of subtropical mangroves on Iriomote Island, southern Japan. The herbivory rate decreased as the concentration of condensed tannins or the tannins: nitrogen ratio increased but did not correlate with the other leaf traits, indicating that leaf herbivory rates are mainly driven by condensed tannins rather than by leaf nutrient concentrations or physical/mechanical traits. In the seaward and one rhizophoraceous species, the herbivory rates were higher in summer than in winter and differed among leaf phenotypes. However, no clear pattern was observed among leaf status across species. Our results suggest that the grazing pathway in mangrove forests is mainly regulated by the concentration of condensed tannins in leaves, often varying with the season and leaf phenotype. Understanding these mechanisms is critical for a comprehensive appreciation of the high productivity of and nutrient cycling in mangrove forest ecosystems.