A Microbial Functional Group‐Based CH₄ Model Integrated Into a Terrestrial Ecosystem Model: Model Structure, Site‐Level Evaluation, and Sensitivity Analysis

Abstract

Wetlands are one of the most important terrestrial ecosystems for land-atmosphere CH 4 exchange. A new process-based, biophysical model to quantify CH 4 emissions from natural wetlands was developed and integrated into a terrestrial ecosystem model (Integrated Biosphere Simulator). The new model represents a multisubstance system (CH 4 , O 2 , CO 2 , and H 2 ) and describes CH 4 production, oxidation, and three transport processes (diffusion, plant-mediated transport, and ebullition). The new model uses several critical microbial mechanisms to represent the interaction of anaerobic fermenters and homoacetogens, hydrogenotrophic, and acetoclastic methanogens, and methanotrophs in CH 4 production and oxidation. We applied the model to 24 different wetlands globally to compare the simulated CH 4 emissions to observations and conducted a sensitivity analysis. The results indicated that (1) for most sites, the model was able to capture the magnitude and variation of observed CH 4 emissions under varying environmental conditions; (2) the parameters that regulate dissolved organic carbon and acetate production, and acetoclastic methanogenesis had the significant impact on simulated CH 4 emissions; (3) the representation of the process components of CH 4 cycling showed that CH 4 oxidation was about half or more of CH 4 production, and plant-mediated transport was the dominant pathway at most sites; and (4) the seasonality of simulated CH 4 emissions can be controlled by soil temperature, water table position, or combinations thereof.Plain Language Summary CH 4 emission from wetlands is an important part of global carbon cycle. A new process-based model was developed to quantify the CH 4 emission from wetlands. The new model considered main microbial mechanisms and transport processes in wetland CH 4 cycling, and the modeled results matched the observed CH 4 emissions well at evaluation sites globally. A sensitivity analysis indicated the important role of parameters that controlled dissolved organic carbon and acetate production and acetoclastic methanogenesis. The assessment of process components of CH 4 cycling demonstrated the importance of CH 4 oxidation and plant-mediated transport in wetland CH 4 emission.

Water flow controls the spatial variability of methane emissions in a northern valley fen ecosystem

“…Projection of global peatland CH 4 emissions under different climate change scenarios is a major challenge due to the reported variabilities in emissions and also because of the interactions between the various environmental predictors (Strack and Waddington, 2007;Strack et al, 2004;Weltzin et al, 2000;Zhang et al, 2002). Our study further highlights that the impacts of climate change on CH 4 emissions in flowthrough peatland systems are even more complicated due to the additional effects of the flowing water, which poses a challenge for accurate predictions of the global CH 4 budget.…”

Methane Emissions Offset Net Carbon Dioxide Uptake From an Alpine Peatland on the Eastern Qinghai‐Tibetan Plateau

“…Moreover, winter was not dormant in terms of CO 2 and CH 4 production, even though T soil at 10 cm depth and T air dropped below zero for 98% and 76% of the wintertime of 2014 and 2015, respectively. During the wintertime, CO 2 and CH 4 emissions from peatlands can still occur through the frozen or snow‐covered soils via diffusion and transportation through the chimney effect led by dead plant tissues and ice cracks and also through the burst emissions caused by rapid ST and freezing (Alm et al., 1999; Mastepanov et al., 2008; C. Song et al., 2020). The large amounts of CO 2 ‐eq emissions during the non‐growing season were in accordance with previous studies, which have recently highlighted that the overall C and GHG budgets may be underestimated without an accurate assessment for the non‐growing season emissions (Aurela et al., 2002; Commane et al., 2017; Natali et al., 2019; W. Song et al., 2015).…”

“…Moreover, winter was not dormant in terms of CO 2 and CH 4 production, even though T soil at 10 cm depth and T air dropped below zero for 98% and 76% of the wintertime of 2014 and 2015, respectively. During the wintertime, CO 2 and CH 4 emissions from peatlands can still occur through the frozen or snow-covered soils via diffusion and transportation through the chimney effect led by dead plant tissues and ice cracks and also through the burst emissions caused by rapid ST and freezing (Alm et al, 1999;Mastepanov et al, 2008;C. Song et al, 2020).…”

Water Flow Controls the Spatial Variability of Methane Emissions in a Northern Valley Fen Ecosystem

“…Similar to the CH4 response to T5, higher DO20 values also reduced the impact of WT position on CH4 emissions. Both responses highlight the importance of oxidation when considering how CH4 emissions respond to environmental changes (Song et al, 2020). The patterns might also indicate higher CH4 production under warmer conditions within the catchment and, consequently, on higher CH4 concentrations in the flowing water (Juutinen et al, 2013).…”