EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

How will forest soils ‘breathe’ in 2050? Soil respiration of CO2, CH4 and N2O under elevated atmospheric CO2.

Alex Armstrong
Alex Armstrong
  • University of Birmingham, Birmingham Institute of Forest Research, Geography, Earth and Environmental Science, United Kingdom of Great Britain – England, Scotland, Wales (

Soil respiration is a measure of the flux of greenhouse gases and accounts for the release and uptake of CO2, CH4 and N2O. It is a function of heterotrophic microbial activity through the mineralisation and immobilisation of organic matter and the symbiotic relations formed in the rhizosphere, contributing to the autotrophic component. It is a primary process within woodlands that contribute to the efflux of CO2, the sink capacity of CH4 and the variable flux of N2O. Understanding how woodland soils will react to rising atmospheric CO2 levels is critical for budgeting, modelling, and providing insightful management strategies for global forests. The Birmingham Institute of Forest Research is a Free Air Carbon Enrichment facility (BIFoR-FACE), whereby the seasonal and diurnal fumigation of CO2 is closely controlled. Providing localised and enriched atmospheric CO2 levels across the canopy of a mature temperate Oak dominant woodland that is representative of 2050 levels.

The flux of CO2 from the soil has been continuously measured within fumigated treatment (eCO2) and ambient control (aCO2) arrays since 2017, with capabilities to additionally measure CH4 and N2O being added in 2020. Across all arrays, CO2 fluxes showed significant negative correlations with soil moisture but significant positive correlations with soil temperature. Initial trends from 2017 - 2020 indicated that eCO2 arrays had a higher efflux of CO2 relative to paired aCO2 arrays, with this pattern switching in 2021. During the 2021 and 2022 fumigation seasons, eCO2 arrays have seen a decline in the efflux of CO2, to levels lower than aCO2 plots. Mean values during 2022 for the efflux of CO2 within eCO2 arrays were 2.63 μmol m-2 s-1 (n = 18762) versus 3.62 μmol m-2 s-1 (n = 22856) for aCO2 arrays. Uptake of CH4 and efflux of N2O were not significantly different between arrays, although eCO2 arrays had lower CH4 uptake and N2O efflux. Indicating a potential decline in the efflux of CO2 but a reduced uptake of CH4 from temperate woodlands under future atmospheric conditions. Further investigation will now look to understand the mechanistic drivers behind these changes, focusing on the microbial heterotrophic contribution as a potential mediator of these noted flux rates changes under eCO2

How to cite: Armstrong, A.: How will forest soils ‘breathe’ in 2050? Soil respiration of CO2, CH4 and N2O under elevated atmospheric CO2., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8621,, 2023.