The Under-Appreciated Potential of Restoration in Southeastern USA Pocosin Peatlands to Reduce Large-Scale Carbon Losses to Microbial Oxidation and Fire.

Background/Question/Methods

At COP26, peatlands received renewed attention for their potential in global carbon cycles, with particular emphasis on peatland restoration. While considerable attention has been paid to restoration peatlands in the Northern regions of the Continental United States, far less is known about the effects of restoration in the subtropical found on the coastal plains of the Southeastern USA. Unlike northern peatlands, the organic matter in the southeastern peatlands is derived from wood, with differing CO2 and CH4 emissions responses to water table depth. In addition, many southeastern peatlands have been drained for agriculture or forestry, leaving them susceptible to the rapid release of greenhouse gases (CO2, CH4, and N2O) through microbial decomposition and disastrous ground fires. Using eddy covariance techniques, we present the first known quantifications of CO2 emissions from drained shrubby evergreen peatlands, known as short pocosins. We model hydrologic restoration's effects on microbial CO2 emissions and the likelihood of catastrophic carbon losses to smoldering ground fires using a probabilistic approach relating peat ignition likelihood to soil moisture and water table depth.

Results/Conclusions

We quantified CO2 emissions from microbial oxidation of peat in drained short pocosins using Eddy covariance techniques; the first such estimates have been published. We also developed a model relating net ecosystem exchange (NEE) to water table level and solar radiation. In a drained state, the net carbon loss to the atmosphere from the short pocosins was 21.2 Mg CO2 ha−1 yr−1. Under a restored modeling scenario where the annual mean water table depth (WTD) was decreased from 60 cm to 30 cm, projected carbon losses fell to only 2 Mg CO2 ha−1 yr−1. If the WTD was decreased to 20 cm, the peatlands became net carbon sinks, with a predicted NEE of -3.3 Mg CO2 ha−1 yr−1. Static chamber measurements showed CH4 and N2O were minor components (2%) of annual greenhouse gas (GHG) emissions from restored short pocosins. Additionally, model results predict restoration will reduce carbon losses to ground fires by an additional 20 to 30 Mg CO2 ha−1 yr−1. The restoration of similar drained peatlands in the southeastern US could prevent the emission of between 1 to 1.6 million Mg of CO2 to the atmosphere each year.