Greenhouse gas fluxes from cold-region wetland soil

The vast stores of soil carbon in the cold regions of the world are stable, in part, due to the low temperatures of the region that inhibit decomposition processes. However, climate warming is likely to promote microbial activity underground. Microbial respiration results in more respiration products like carbon dioxide, and methane being released directly to the atmosphere. The rate that these greenhouse gasses (GHGs) are respired are influenced by more than just temperature; soil composition, surface vegetation, and soil moisture are a few examples of other variables that are known to impact GHG emissions. Especially in cold regions where perennially frozen soils (permafrost) is present, warming soil temperatures can bring entire regime changes to the soil column as ice-rich soils thaw, and transition to water-saturated wetlands.

The exact mechanisms driving the timeline and scale of soil carbon being respired to the atmosphere is not yet understood well enough to be effectively incorporated into global models of Earth’s climate. This is especially true for high-latitude soils, where the remoteness and heterogeneity of the landscape further complicates modeling efforts. In this postdoc project, we will use GHG flux measurements collected from arctic soils along transects of disturbance gradients to parse out what may be driving the ubiquitous methane emission we have seen from preliminary analysis of the data.

Here in Denmark, a large proportion of the nation's wetland soils have been subjected to disturbances through changing land uses, such as the conversion of the land for use in agriculture. Recently, the value of wetlands as hydrological buffers, wildlife habitat, and carbon sequestration (and more) has been gaining recognition. With this recognition, interest has grown in “rewetting” efforts. Rewetting a wetland largely involves restoring the traditional flow of water to low-lying areas, in an effort to revitalize lands that were previously wetlands. Another part of this postdoc project will be to help guide masters students with an incubation experiment of recently rewetted soils from a wetland in the region. With the meso-scale experimental setup, we will be able to monitor the soil's GHG emission under different nutrient and temperature conditions while keeping the soil column intact.

As our understanding of the many benefits to restoring wetlands expands, so too is our understanding of the best practices in how exactly to ensure the rewetting efforts meet the goals of the community living within the watershed. As with all research, our efforts to understand the many mysteries of wetland soils is incomplete, until it is communicated outside the laboratory. To meet this goal, I am helping to organize a workshop for stakeholders and academic researchers to come together in Vestjylland, and share their experiences with different re-wetting strategies.