CLIMATE-CHANGE DISEQUILIBRIUM OF BOREAL PERMAFROST PEATLANDS CAUSED BY LOCAL PROCESSES

Boreal forest and tundra are the biomes expected to experience the gre atest warming during the course of the next century. The transient res ponses of boreal peatlands to climate change could be more complex tha n a simple large release of carbon and rapid migrations of vegetation and permafrost. Here we used alternative models to demonstrate that lo cal processes typical of permafrost peatlands control carbon and veget ation dynamics in ways that strongly mediate effects of regional tempe rature gradients. Regional temperature affected stability and thaw rat e. Thaw rate increased with mean annual temperature, and rates have ac celerated within the last 50 yr. Local factors exerted a strong; influ ence on stability, the levels of which were highest in three of the fo ur temperature zones studied along the shaded south-southwest edges of collapse scars. The presence of Sphagnum fuscum cover increased stabi lity. In all zones, survey points with S. fuscum showed more than twic e the stability of points with feather moss, lichen, or no vegetation. In a direct model comparison between regional and local control, loca l factors were more important. Our results suggest that local processe s mediate the effects of regional climate, and an accurate representat ion of ecosystem dynamics benefits from both local and regional proces ses.