November 07, 2023

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Interannual Patterns of Soil Carbon Dioxide Fluxes Driven by Moisture in Two Montane Forests

Carbon dioxide flux was related to the prior winter’s snowfall and current summer’s rainfall, with greater sensitivity to rainfall.

Relationship between total water year precipitation inputs and mean soil carbon dioxide (CO2) flux for aspen and conifer forests (A). Differential sensitivity of soil CO2 flux to winter and summer precipitation inputs (B).

[Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0) from Carbone, M. S., et al. "Interannual Precipitation Controls on Soil CO2 Fluxes in High Elevation Conifer and Aspen Forests." Environmental Research Letters 18 (124009), (2023). DOI:10.1088/1748-9326/ad07b5.]

The Science

For nearly a decade, a team of researchers measured the amount of carbon dioxide (CO2) produced in soil in high-elevation mixed conifer and aspen forests. The amount of CO2 produced during the summer was controlled by prior winter snowfall and current summer rains. Summer rainfall, while making up only 10 to 35% of the total moisture inputs, was particularly important for stimulating soil CO2 fluxes due to the timing and location of the moisture.

The Impact

This study summarizes outcomes from a long and continuous dataset of soil CO2 that allows for unique analysis of interannual variability of soil CO2 flux in relation to precipitation. Results are important for understanding forest functioning as snowfall and rainfall amounts are being altered with climate change, and addresses how past, current, and future precipitation changes may influence the amount of carbon returned to the atmosphere.

Summary

Long-term soil CO2 emission measurements are necessary for detecting trends and interannual variability in the terrestrial carbon cycle. Such records are becoming increasingly valuable as ecosystems experience altered environmental conditions associated with climate change. From 2013 to 2021, researchers continuously measured soil CO2 concentrations in two dominant high-elevation forest types, mixed conifer and aspen, in the upper Colorado River basin.

The team quantified soil CO2 flux during the summer months and found that the mean and total CO2 flux in both forests was related to the prior winter’s snowfall and current summer’s rainfall, with greater sensitivity to rainfall. A decline occurred in surface soil CO2 production, which was attributed to warming and a decrease in the amount and frequency of summer rains. Results demonstrated strong precipitation control on soil CO2 flux in mountainous regions, which has important implications for carbon cycling under future environmental change.

Principal Investigator

Mariah Carbone
Northern Arizona University
[email protected]

Program Manager

Paul Bayer
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

The Rocky Mountain Biological Laboratory provided financial support. Instrumentation was supported by the National Science Foundation’s (NSF) Division of Biological Infrastructure under Grant no. 0821369. Support was also received from the National Oceanic and Atmospheric Administration’s Climate and Global Change Postdoctoral Fellowship, the National Center for Ecological Analysis and Synthesis, which is funded by NSF Grant no. EF-0553768), and the U.S. Department of Energy’s Biological and Environmental Research program under Grant numbers DE-SC0021139, DE-SC0024218, and DE-SC0019210).

References

Carbone, M. S., et al. "Interannual Precipitation Controls on Soil CO2 Fluxes in High Elevation Conifer and Aspen Forests." Environmental Research Letters 18 (124009), (2023). https://doi.org/10.1088/1748-9326/ad07b5.