Vegetation Differentiation of Arctic Patterned-ground Ecosystems
Abstract
Nonsorted circles, nonsorted polygons and earth hummocks are common ground surface features in arctic regions. They are caused by a variety of physical processes common to permafrost regions including frost- cracking and frost-heaving. Here we describe the vegetation of these frost features at 10 study sites along a N- S-transect from Ellef Ringnes Island, Canada (78° N) to the Arctic Foothills, Alaska (68° N) covering all five bioclimatic subzones of the Arctic. We established 192 relevés to analyze floristic and ecological differences of circles/intercircles, polgygons/interpolygons, and hummocks/interhummocks and classified the vegetation according to the Braun-Blanquet sorted-table method. Environmental factors were correlated with the vegetation data using various ordination techniques (nonmetric multidimensional scaling, detrended correspondence analysis). We identified 19 plant communities associated with the different permafrost features. Their floristic composition as well as their cover/abundance was strongly related to the main ecological gradients, i.e. bioclimate, soil moisture, disturbance, and pH. In general, frost-heave communities are dominated by lichens and forbs while adjacent communities have a greater moss, graminoid and dwarf-shrub cover. Frost-heave features also have greater thaw depth, more bare ground, thinner organic horizons, and lower soil moisture than the surrounding tundra. The morphology of the investigated patterned ground forms changes along the climatic gradient with nonsorted polygons dominating in the northern sites and nonsorted circles dominating in southern sites. Given the large contrast in floristic composition and ecological properties between nonsorted circles and intercircles we would expect to see climate-change induced vegetation dynamics to be most strongly manifested in these features as compared to tundra vegetation without frost-heave patterns.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.C44A..05K
- Keywords:
-
- 9315 Arctic region (0718;
- 4207)