Effects of ice-wedge degradation and warming on Arctic tundra vegetation across a climatic gradient using a nitrogen-based model

Ice-wedge polygons in Arctic tundra landscapes influence hydrology, nutrients, thermal regimes, and vegetation. Ice-wedges are particularly vulnerable to warming events, and widespread degradation has been observed in recent decades. While increased vegetation growth is predicted to offset some of the nutrient losses from thawing Arctic soils, evolving Arctic vegetation carbon and nitrogen stocks are poorly understood. To explore effects of warming and ice-wedge degradation on Arctic vegetation, we used aboveground plant biomass data from stages of ice-wedge degradation at two northern Arctic tundra sites (Jago River and Prudhoe Bay, AK) to parameterize and test a nutrient-based, plant community and ecosystem model (ArcVeg) incorporating ice-wedges within a landscape for different Arctic tundra locations. Warming increased both aboveground and belowground biomass but introducing ice-wedge degradation led to shrub loss and a shift from terrestrial moss and shrub-dominated communities to aquatic moss and graminoid-dominated communities. In northern locations, degradation reduced vegetation C and N stocks due to biomass loss, whereas at the southern location, total plant C and N increased substantially due to moss proliferation. Model predictions suggest that ice-wedge degradation effects are accentuated under warming, and southern Arctic tundra aquatic moss proliferation may offset or even exceed biomass lost.