Hysteretic temperature sensitivity of wetland CH 4 fluxes explained by substrate availability and microbial activity

Chang, Kuang-Yu; Riley, William J.; Crill, Patrick M.; Grant, Robert F.; Saleska, Scott R.

Methane (CHinline-formula4) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CHinline-formula4 emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CHinline-formula4 production and emission. While statistically consistent apparent CHinline-formula4 emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Here, we show that apparent CHinline-formula4 emission temperature dependencies inferred from year-round chamber measurements exhibit substantial intra-seasonal variability, suggesting that using static temperature relations to predict CHinline-formula4 emissions is mechanistically flawed. Our model results indicate that such intra-seasonal variability is driven by substrate-mediated microbial and abiotic interactions: seasonal cycles in substrate availability favors CHinline-formula4 production later in the season, leading to hysteretic temperature sensitivity of CHinline-formula4 production and emission. Our findings demonstrate the uncertainty of inferring CHinline-formula4 emission or production rates from temperature alone and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.

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Chang, Kuang-Yu / Riley, William J. / Crill, Patrick M. / et al: Hysteretic temperature sensitivity of wetland CH4 fluxes explained by substrate availability and microbial activity. 2020. Copernicus Publications.

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