Methane flux from peatland ecosystems in response to environmental change: Insights from the past and opportunities for the future

Background/Question/Methods

In addition to acting as a globally significant store of carbon, peatlands are also an important natural source of methane (CH₄) to the atmosphere.  Given the high global warming potential of CH₄, understanding the response of peatland CH₄ flux to environmental change - including temperature, water-table level, and elevated atmospheric CO₂ - is crucial for understanding the future role of peatlands in the global climate.  CH₄ flux is the result of CH₄ production, consumption and transport and is regulated by both plant and microbial activities.  Unraveling the mechanistic controls of these activities remains a challenge for both understanding and modeling the response of peatland CH₄ flux to environmental change.

Results/Conclusions

Synthesis of past research exploring the response of peatland CH₄ flux to environmental change reveals a number of consistent patterns, most notably: (1) warmer temperatures increases CH₄ flux, (2) wetter conditions increase CH₄ flux, and (3) elevated CO₂ increases CH₄ flux.  Projects exploring the interactive effects of these environmental changes are limited, but suggest that interactions are important.

Increasingly, there is a growing body of work demonstrating that the mechanistic controls of these responses are complex and involve links between plant, microbe and soil dynamics.   For example, increased CH₄ production in response to temperature is linked to a number of non-methanogenic microbial activities, including: fermentation, acetate production, and the competitive reduction of inorganic and organic terminal electron acceptors.  The response of CH₄ flux to water-table level may be related not only to oxygen sensitivity of CH₄ production and consumption, but also to longer-term shifts in plant community structure.   Elevated CO₂ impacts are frequently linked to the increase in organic carbon substrates associated with increased plant productivity.  Comparative studies in different peatland types (e.g., bogs and fens) suggest that the controls of CH₄ dynamics likely differ between different peatlands for reasons which are not well understood.  Taken together, past research highlights the importance of developing stronger mechanistic models of production, consumption, transport, and ultimately flux of CH₄ from peatlands for exploring links between peatlands and environmental change.