Changes in vegetation properties in permafrost affected peatland ecosystem in northern Norway undergoing rapid permafrost degradation

Permafrost degradation is expected to release large amounts of greenhouse gasses to the atmosphere, creating positive feedback to climate warming. The greenhouse balance is largely dominated by microbial decomposition of soil organic matter, however, as permafrost thaws the vegetation composition and growth rate changes and increases the potential to fix carbon in the ecosystem. The aspect of vegetation change, therefore, is worth noting independent of greenhouse emissions from soils under permafrost thawing and climate warming. We investigate how vegetation properties change with permafrost thawing and artificial warming at a natural gradient of permafrost thawing and natural succession and using open top chambers following the International Tundra Experiment (ITEX) protocol at a permafrost affected peatland palsa-mire ecosystem in northern Norway undergoing rapid permafrost degradation followed by natural succession knowns as the Iškoras site. The permafrost affected peat plateau called ‘palsa’ is dominated by evergreen dwarf shrubs such as Empetrum nigrum. As permafrost thaws and palsa collapses, the wet soil conditions promote vegetation shift from E. nigrum to more hydrophilic deciduous shrubs such as Rubus chamaemorus. Eventually, the waterlogged mires will undergo natural succession dominated by non-vascular vegetation such as mosses and lichen as well as sedges. This vegetation transition corresponds to a shift in functional traits from conservative to resource acquisitive. Warming primarily led to an increase in size related traits. Furthermore, vegetation greenness (NDVI) showed a different development over the growing season in response to permafrost thaw and warming. The total biomass and composition have high implications for understanding ecosystem carbon balance as well as CH₄ emissions in this ecosystem under rapid permafrost degradation.