Climate change disequilibrium of boreal permafrost peatlands caused by local processes

Boreal forest and tundra are the biomes expected to experience the greatest warming during the course of the next century. The transient responses of boreal peatlands to climate change could be more complex than a simple large release of carbon and rapid migrations of vegetation and permafrost. Here we used alternative models to demonstrate that local processes typical of permafrost peatlands control carbon and vegetation dynamics in ways that strongly mediate effects of regional temperature gradients. Regional temperature affected stability and thaw rate. Thaw rate increased with mean annual temperature, and rates have accelerated within the last 50 yr. Local factors exerted a strong influence on stability, the levels of which were highest in three of the four temperature zones studied along the shaded south-southwest edges of collapse scars. The presence of Sphagnum fuscum cover increased stability. In all zones, survey points with S. fuscum showed more than twice the stability of points with feather moss, lichen, or no vegetation. In a direct model comparison between regional and local control, local factors were more important. Our results suggest that local processes mediate the effects of regional climate, and an accurate representation of ecosystem dynamics benefits from both local and regional processes.