STEPPE VEGETATION ON SOUTH-FACING SLOPES OF PINGOS, CENTRAL ARCTIC COASTAL-PLAIN, ALASKA, USA

The hypothesized presence of large regions of grass and forb-dominated "steppe tundra" across Alaska and Siberia during the Pleistocene glacial epochs has led to a search for modern analogs. Evidence is presented for the presence of steppe vegetation on south-facing slopes and summits of pingos within the central Arctic Coastal Plain of Alaska. Vegetation, floristics, soils, and climatic factors are each considered, and together support the idea of an ecologically-physiognomically defined steppe on these sites. Grasses and forbs dominate this vegetation, and Dryas integrifolia, which is dominant in most dry sites regionally, is absent or has only minimal cover. Although the floristic evidence indicates that the pingo vegetation is most strongly related to the circumpolar arctic vegetation, the steppe-like vegetation has more North American-Asian and low arctic taxa than do other sites. Soils are Pergelic Cryoborolls, and the microclimates on south slopes have greater daily and annual fluctuations than do other microsites. Other pingo vegetation is related to fellfield and snowbeds. These communities represent the northernmost known examples of steppe in North America, and help explain the complex relationships that can exist within the vegetation of well-drained arctic sites.