Carbon flux in Icelandic heathlands; a contribution to LULUCF Tier 2 emission factors

Climate change due to anthropogenic factors is of global concern. Monitoring and reporting all potential carbon sinks and sources are therefore important. Iceland adopted the Paris Agreement in 2016 and decided in 2019 to participate jointly with the EU in meeting the Paris Agreement commitments. This requires compiling and reporting emission data for the whole country. Land use, land use change and forestry (LULUCF) is the main contributing factor of GHG emissions in Iceland. However, heathlands are the spatially largest of the LULUCF grassland category although not the largest contributor to CO₂ emissions, as that is the wetland converted to grassland subcategory. Emission from the heathlands subcategory is currently uncertain and still rely on the IPCC default Tier 1 emission factors. In this ongoing research the aim is to improve the understanding of the carbon processes in Icelandic heathlands and to push the national accounting for grasslands to a higher tier. Since 2022 CO₂ emissions have been measured weekly at different heathland sites during the summer months; May to September. Currently, around 50 plots are active. Each plot is comprised of 9 to 12 hollow 12 cm cylinders driven roughly 10 cm into the ground in clusters of 3. EGM-5 portable CO₂ gas analyzer with a CPY-5 transparent chamber is used for field measurements, first with the chamber uncovered then covered. Other measurements include soil temperature, soil moisture, air temperature and PAR. Preliminary results show a seasonal trend of sequestration increase later in the summer. There is a high variability in the data but an overall higher sequestration rate than emission rate is detected. Cloud cover and weather conditions have a clear effect on the carbon flux. This variability underlines the importance of long-term series for such datasets.