Nitrogen deposition accelerates soil carbon sequestration in tropical forests

Xiankai Lu, Peter M. Vitousek, Qinggong Mao, Frank S. Gilliam, Yiqi Luo, Benjamin L. Turner, Guoyi Zhou, Jiangming Mo

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Terrestrial ecosystem carbon (C) sequestration plays an important role in ameliorating global climate change. While tropical forests exert a disproportionately large influence on global C cycling, there remains an open question on changes in below-ground soil C stocks with global increases in nitrogen (N) deposition, because N supply often does not constrain the growth of tropical forests. We quantified soil C sequestration through more than a decade of continuous N addition experiment in an N-rich primary tropical forest. Results showed that long-term N additions increased soil C stocks by 7 to 21%, mainly arising from decreased C output fluxes and physical protection mechanisms without changes in the chemical composition of organic matter. A meta-analysis further verified that soil C sequestration induced by excess N inputs is a general phenomenon in tropical forests. Notably, soil N sequestration can keep pace with soil C, based on consistent C/N ratios under N additions. These findings provide empirical evidence that below-ground C sequestration can be stimulated in mature tropical forests under excess N deposition, which has important implications for predicting future terrestrial sinks for both elevated anthropogenic CO2 and N deposition. We further developed a conceptual model hypothesis depicting how soil C sequestration happens under chronic N deposition in N-limited and N-rich ecosystems, suggesting a direction to incorporate N deposition and N cycling into terrestrial C cycle models to improve the predictability on C sink strength as enhanced N deposition spreads from temperate into tropical systems.

Original languageEnglish (US)
Article numbere2020790118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number16
DOIs
StatePublished - Apr 20 2021

Keywords

  • Atmospheric nitrogen deposition
  • Below-ground carbon sequestration
  • Global changes
  • Nitrogen biogeochemistry
  • Soil carbon storage

ASJC Scopus subject areas

  • General

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