Physical characteristics of peat and their influence on peat CO2 emission potential in a drained boreal peatland forest

Peatlands are a significant global storage of carbon (C), but also major sources of nutrients and dissolved organic carbon (DOC) to surface waters. Export of DOC from peatlands to watercourses cause emissions of  carbon dioxide (CO₂) due to degradation of DOC, as well as enhances the brownification of surface waters, altering the ecological networks of the aquatic ecosystems. Managed peatland forests are hotspots for DOC export into downstream water bodies due to forestry practices such as harvesting and drainage. Water table, soil oxygen availability and vegetation control the release and transport of DOC.

Drainage of peatlands also alters the physical characteristics of peat (Word et al., 2022). However, the role of these peat characteristics in the processes and release of DOC, as well as their influence on the lateral fluxes of carbon from forested peatlands, remains unknown.

In this contribution, we present results from a laboratory experiment where the physical properties of peat and their relationship to peat decomposition are studied in a minerotrophic, nutrient-rich peatland forest that has been drained for ~80 years. The peat for the study was collected from the field site, located in southern Finland, into 50 cm columns along three transects. The transects  extend from 1 to 30 meter distance from the  ditch. In laboratory, the bulk density and water retention characteristics of the peat will first be determined in relation to distance to the ditch. The CO₂ emission potential is then defined as the function of these peat properties. This is done by measuring the CO₂ fluxes of the peat with a chamber enclosure method, using a Li-7810 online CH₄-CO₂-H₂O analyser.

The results of this experiment will increase the process-level understanding of the mechanisms that drive the export of DOC from peatlands. The produced data will be further utilized in an ecosystem model, to be used in assessing and evaluating environmental impacts of forest management practises.

 

References

Word CS, McLaughlin DL, Strahm BD, Stewart RD, Varner JM, Wurster FC, Amestoy TJ, Link NT. 2022. Peatland drainage alters soil structure and water retention properties: Implications for ecosystem function and management. Hydrological Processes 36: e14533.