Dinitrogen Emissions Dominate Nitrogen Gas Emissions From Soils With Low Oxygen Availability in a Moist Tropical Forest

Authors

Maya Almaraz, Princeton University
Peter M. Groffman, Cary Institute of Ecosystem Studies
Whendee L. Silver, University of California - Berkeley
Steven J. Hall, Iowa State University
Yang Lin, University of California - Berkeley
Christine S. O'Connell, Chapman UniversityFollow
Stephen Porder, Brown University

Document Type

Article

Publication Date

1-11-2023

Abstract

Lowland tropical forest soils are relatively N rich and are the largest global source of N₂O (a powerful greenhouse gas) to the atmosphere. Despite the importance of tropical N cycling, there have been few direct measurements of N₂ (an inert gas that can serve as an alternate fate for N₂O) in tropical soils, limiting our ability to characterize N budgets, manage soils to reduce N₂O production, or predict the future role that N limitation to primary productivity will play in buffering against climate change. We collected soils from across macro- and micro-topographic gradients that have previously been shown to differ in O₂ availability and trace gas emissions. We then incubated these soils under oxic and anoxic headspaces to explore the relative effect of soil location versus transient redox conditions. No matter where the soils came from, or what headspace O₂ was used in the incubation, N₂ emissions dominated the flux of N gas losses. In the macrotopography plots, production of N₂ and N₂O were higher in low O₂ valleys than on more aerated ridges and slopes. In the microtopography plots, N₂ emissions from plots with lower mean soil O₂ (5%–10%) were greater than in plots with higher mean soil O₂ (10%–20%). We estimate an N gas flux of ∼37 kg N/ha/yr from this forest, 99% as N₂. These results suggest that N₂ fluxes may have been systematically underestimated in these landscapes, and that the measurements we present call for a reevaluation of the N budgets in lowland tropical forest ecosystems.

Comments

This article was originally published in Journal of Geophysical Research: Biogeosciences, volume 128, issue 1, in 2023. https://doi.org/10.1029/2022JG007210

Recommended Citation

Almaraz, M., Groffman, P. M., Silver, W. L., Hall, S. J., Lin, Y., O’Connell, C., & Porder, S. (2023). Dinitrogen emissions dominate nitrogen gas emissions from soils with low oxygen availability in a moist tropical forest. Journal of Geophysical Research: Biogeosciences, 128, e2022JG007210. https://doi.org/10.1029/2022JG007210

Copyright

American Geophysical Union