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Background and aims <p>Interactions among ectomycorrhizal (ECM) trees, fungal communities and ecosystem-scale N availability can drive carbon (C) and nitrogen (N) cycling at the tree scale, but these mechanisms have largely been tested in N-limited ecosystems. We investigated the role of ECM and saprotrophic (SAP) fungal communities in suppressing inorganic N cycling beneath ECM trees in a tropical rainforest where biotic and abiotic factors can drive rapid N cycling at the ecosystem scale. Based on knowledge from temperate and boreal forests, we expected to observe a decrease in ECM:SAP fungal ratios and a shift in the ECM fungal community composition with increasing inorganic N availability.</p> Methods <p>We quantified fungal community metrics and soil chemical properties in a long-term N addition experiment located in a lower montane tropical rainforest. We measured the natural abundance stable N isotopic composition of litter and soil organic matter to indicate contributions of ECM fungi to ecosystem N cycling.</p> Results <p>We found that the stable N isotopic composition of leaf litter correlated with a shift in fungal community composition between control and N addition plots. N addition did not affect ECM:SAP fungal ratios or ECM community composition, but decreased the relative abundance of <i>Cortinarius</i>, which are peroxidase-producing ECM fungi.</p> Conclusions <p>We did not find evidence that interguild competition or specific ECM functional traits drove conservative N cycling beneath ECM trees. This suggests that tree-scale N limitation may be partially mediated by ecosystem-scale N availability that is distinct in tropical rainforest compared to temperate and boreal forests.</p>

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Nitrogen addition alters interactions between ectomycorrhizal host trees and fungal communities in a mixed mycorrhizal tropical rainforest

  • 期刊论文

  • 发表日期：

    2025年3月4日

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  • Georgia S. Seyfried,
  • Joseph D. Edwards,
  • James W. Dalling,
  • Angela D. Kent,
  • Wendy H. Yang

摘要

Background and aims

Interactions among ectomycorrhizal (ECM) trees, fungal communities and ecosystem-scale N availability can drive carbon (C) and nitrogen (N) cycling at the tree scale, but these mechanisms have largely been tested in N-limited ecosystems. We investigated the role of ECM and saprotrophic (SAP) fungal communities in suppressing inorganic N cycling beneath ECM trees in a tropical rainforest where biotic and abiotic factors can drive rapid N cycling at the ecosystem scale. Based on knowledge from temperate and boreal forests, we expected to observe a decrease in ECM:SAP fungal ratios and a shift in the ECM fungal community composition with increasing inorganic N availability.

Methods

We quantified fungal community metrics and soil chemical properties in a long-term N addition experiment located in a lower montane tropical rainforest. We measured the natural abundance stable N isotopic composition of litter and soil organic matter to indicate contributions of ECM fungi to ecosystem N cycling.

Results

We found that the stable N isotopic composition of leaf litter correlated with a shift in fungal community composition between control and N addition plots. N addition did not affect ECM:SAP fungal ratios or ECM community composition, but decreased the relative abundance of Cortinarius, which are peroxidase-producing ECM fungi.

Conclusions

We did not find evidence that interguild competition or specific ECM functional traits drove conservative N cycling beneath ECM trees. This suggests that tree-scale N limitation may be partially mediated by ecosystem-scale N availability that is distinct in tropical rainforest compared to temperate and boreal forests.