Representing Methane Emissions from Wet Tropical Forest Soils Using Microbial Functional Groups Constrained by Soil Diffusivity

Authors

Debjani Sihi, Oak Ridge National Laboratory
Xiaofeng Xu, San Diego State University
Mónica Salazar Ortiz, University of Hamburg
Christine S. O'Connell, Chapman UniversityFollow
Whendee L. Silver, University of California - Berkeley
Carla López-Lloreda, University of New Hampshire, Durham
Julia M. Brenner, Oak Ridge National Laboratory
Ryan K. Quinn, Oak Ridge National Laboratory
Jana R. Phillips
Brent D. Newman, Los Alamos National Laboratory
Melanie A. Mayes, Oak Ridge National Laboratory

Document Type

Article

Publication Date

3-15-2021

Abstract

Tropical ecosystems contribute significantly to global emissions of methane (CH₄), and landscape topography influences the rate of CH₄ emissions from wet tropical forest soils. However, extreme events such as drought can alter normal topographic patterns of emissions. Here we explain the dynamics of CH₄ emissions during normal and drought conditions across a catena in the Luquillo Experimental Forest, Puerto Rico. Valley soils served as the major source of CH₄ emissions in a normal precipitation year (2016), but drought recovery in 2015 resulted in dramatic pulses in CH₄ emissions from all topographic positions. Geochemical parameters including (i) dissolved organic carbon (C), acetate, and soil pH and (ii) hydrological parameters like soil moisture and oxygen (O₂) concentrations varied across the catena. During the drought, soil moisture decreased in the slope and ridge, and O₂ concentrations increased in the valley. We simulated the dynamics of CH₄ emissions with the Microbial Model for Methane Dynamics-Dual Arrhenius and Michaelis–Menten (M3D-DAMM), which couples a microbial functional group CH₄ model with a diffusivity module for solute and gas transport within soil microsites. Contrasting patterns of soil moisture, O₂, acetate, and associated changes in soil pH with topography regulated simulated CH₄ emissions, but emissions were also altered by rate-limited diffusion in soil microsites. Changes in simulated available substrate for CH₄ production (acetate, CO₂, and H₂) and oxidation (O₂ and CH₄) increased the predicted biomass of methanotrophs during the drought event and methanogens during drought recovery, which in turn affected net emissions of CH₄. A variance-based sensitivity analysis suggested that parameters related to aceticlastic methanogenesis and methanotrophy were most critical to simulate net CH₄ emissions. This study enhanced the predictive capability for CH₄ emissions associated with complex topography and drought in wet tropical forest soils.

Comments

This article was originally published in Biogeosciences, volume 18, issue 5, in 2025. https://doi.org/10.5194/bg-18-1769-2021

Recommended Citation

Sihi, D., Xu, X., Salazar Ortiz, M., O'Connell, C. S., Silver, W. L., López-Lloreda, C., Brenner, J. M., Quinn, R. K., Phillips, J. R., Newman, B. D., and Mayes, M. A.: Representing methane emissions from wet tropical forest soils using microbial functional groups constrained by soil diffusivity, Biogeosciences, 18, 1769–1786, https://doi.org/10.5194/bg-18-1769-2021, 2021.

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.