Hysteretic Temperature Sensitivity of Wetland CH4 Fluxes Explained by Substrate Availability and Microbial Activity

The Science

Wetland methane (CH₄) emissions are likely increasing and important in global climate change assessments; however, the temperature sensitivity of CH₄ production and emission remains very uncertain. Here researchers from NGEE-Arctic use a well-tested mechanistic ecosystem model to examine the observed apparent CH₄ emission hysteresis to air and soil temperatures. Their simulations indicate that these hysteretic relationships are driven by substrate-mediated microbial and abiotic interactions: seasonal cycles in substrate availability favors CH₄ production later in the season, leading to higher CH₄ production and emission rates at the same temperature.

The Impact

The experimental simulations show substantial intra-seasonal variability in the temperature sensitivity of CH₄ production and emission. These findings demonstrate the uncertainty of inferring CH₄ production or emission rates from temperature alone and highlight the need to properly represent microbial and abiotic interactions in terrestrial biogeochemical models.

Summary

Methane (CH₄) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CH₄ emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CH₄ production and emission. While statistically consistent apparent CH₄ emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Here, researchers from NGEE-Arctic show that apparent CH₄ emission temperature dependencies inferred from year-round chamber measurements exhibit substantial intra-seasonal variability, suggesting that using static temperature relations to predict CH₄ emissions is mechanistically flawed. The model results indicate that this intra-seasonal variability is driven by substrate-mediated microbial and abiotic interactions: seasonal cycles in substrate availability favors CH₄ production later in the season, leading to hysteretic temperature sensitivity of CH₄ production and emission. These findings demonstrate the uncertainty of inferring CH₄emission or production rates from temperature alone and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.

Principal Investigator

William Riley
Lawrence Berkeley National Laboratory
[email protected]

Program Manager

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

Funding

This study was funded by the Genomic Science Program of the United States Department of Energy Office of Biological and Environmental Research under the ISOGENIE (DE-SC0016440) and NGEE-Arctic projects under contract DE- AC02-05CH11231 to Lawrence Berkeley National Laboratory.

References