How do tropical peatland greenhouse gas emissions respond in the immediate aftermath of a fire?

Southeast Asia is a region where forest clearance, drainage of peatlands for agriculture, and ongoing use of fire to ‘manage’ land leads to extensive emissions of greenhouse gases to the atmosphere, and significant disturbance to peatland soils. While recent campaigns investigating tropical peatland fire emissions have improved our knowledge and understanding of ‘direct’ greenhouse gas emissions during fires, there remains a significant gap in our knowledge of the immediate post-fire impacts on peat respiration and methanogenesis. Ongoing research shows that peatland microbial communities (responsible for respiration), including methanogens and methanotrophs (responsible for controlling net methane emissions), are considerably altered following fire disturbance. As such, we hypothesise that peatland fires will lead to significant alterations to GHG emissions, compared to sites that have not burned. Further, we also hypothesise that the magnitude of this post-fire effect will be predictably interrelated to different forms of peatland degradation and land-use history.

Here we present results from seven fire locations (recently burnt) and their corresponding neighbouring control sites (not recently burnt), three of our fire locations were associated with forest clearance fires, while the other four locations were slash fires on oil palm plantations. We characterize the post-fire disturbance emissions of carbon dioxide (CO₂) and methane (CH₄) in situ, in the immediate aftermath of a fire (within days or weeks), and in the subsequent months following a fire at our burn sites. For comparison, we also measure CO₂ and CH₄ emissions from neighbouring control sites that remained unburnt. We find substantial, significant differences in CH₄ emissions between the burn sites and control sites for all seven of our measurement locations. We suggest a number of mechanisms responsible for this post-fire effect, including disturbance to the methanotroph microbial communities at the burn sites, as well as reduced elevation at the burn sites, leading to higher water tables.