Data‐Constrained Projections of Methane Fluxes in a Northern Minnesota Peatland in Response to Elevated CO₂ and Warming

Abstract

Large uncertainties exist in predicting responses of wetland methane (CH4) fluxes to future climate change. However, sources of the uncertainty have not been clearly identified despite the fact that methane production and emission processes have been extensively explored. In this study, we took advantage of manual CH4 flux measurements under ambient environment from 2011 to 2014 at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experimental site and developed a data‐informed process‐based methane module. The module was incorporated into the Terrestrial ECOsystem (TECO) model before its parameters were constrained with multiple years of methane flux data for forecasting CH4 emission under five warming and two elevated CO2 treatments at SPRUCE. We found that 9°C warming treatments significantly increased methane emission by approximately 400%, and elevated CO2 treatments stimulated methane emission by 10.4%–23.6% in comparison with ambient conditions. The relative contribution of plant‐mediated transport to methane emission decreased from 96% at the control to 92% at the 9°C warming, largely to compensate for an increase in ebullition. The uncertainty in plant‐mediated transportation and ebullition increased with warming and contributed to the overall changes of emissions uncertainties. At the same time, our modeling results indicated a significant increase in the emitted CH4:CO2 ratio. This result, together with the larger warming potential of CH4, will lead to a strong positive feedback from terrestrial ecosystems to climate warming. The model‐data fusion approach used in this study enabled parameter estimation and uncertainty quantification for forecasting methane fluxes.

The role of environmental driving factors in historical and projected carbon dynamics of wetland ecosystems in Alaska

“…In contrast, increasing air temperature had a large effect on CH 4 emissions (15.4% AE 3.0% per°C increase at statewide level), primarily due to the additional direct effect of warming soil temperature on accelerated anaerobic decomposition. The positive response of CH 4 emissions to increasing air temperature is supported by recent studies suggesting that terrestrial high-latitude CH 4 emissions are more impacted by changes in temperature than by increased availability of organic matter (Updegraff et al 2001, Turetsky et al 2008, Olefeldt et al 2013, Ma et al 2017.…”

“…CH 4 emissions from wetlands are controlled by many factors, including climate, atmospheric CO 2 concentration, and electron acceptor availability in the soil (Zehnder and Stumm 1988, Wang et al 1993, Whiting and Chanton 1993. In particular, it is expected that CH 4 emissions may be very responsive to soil temperature and moisture changes resulting from climate change (Updegraff et al 2001, Turetsky et al 2008, Olefeldt et al 2013, Ma et al 2017.…”

Forecasting Responses of a Northern Peatland Carbon Cycle to Elevated CO2 and a Gradient of Experimental Warming

“…Thus, the expectation on how long it would take for experimental effects to be observed may be different from real observations. Our EcoPAD platform can update parameters regularly as new data sets become available and reveal when model simulations depart from experimental observations (Huang et al, ; Ma et al, ).…”

Long‐term impacts of warming drive decomposition and accelerate the turnover of labile, not recalcitrant, carbon

“…According to the Bayes' theorem, the posterior probability density function (PDF) PðhjZÞ of model parameters (h) for given observations (Z) was estimated from our prior knowledge of PDF P(h) and a likelihood function of observations PðZjhÞ , Ma et al 2017)…”