28 J. Brown et al. 



tic species include Luzula confusa. Potent ilia hyparctica, Alectoria nigri- 

 cans and Pogonatum alpinum. 



Salix heath (Type II) is characteristic of the sloping creek banks and 

 the centers of some low-centered polygons which drain readily. It occu- 

 pies 1% of the research area. Salix rotundifolia, a prostrate deciduous 

 shrub, Arctagrostis latifolia and Saxifraga nelsoniana characterize this 

 type. The Salix heath has the highest number of forbs (22) and the high- 

 est overall number of species (70) of any of the vegetation types. The 

 sandy soil associated with Salix heath is usually well drained and has the 

 greatest seasonal depth of thaw. 



Carex-Poa meadow (Type III) is the most extensive vegetation type, 

 covering 41% of the research area. Bryophytes, primarily mosses, and 

 lichens cover relatively larger areas than do the graminoids. The mosses 

 Pogonatum alpinum and Dicranum elongatum and the lichens Cetraria 

 richardsonii and Dactylina arctica are characteristic species. The Carex- 

 Oncophorus meadow, Dupontia meadow, and Carex-Eriophorum mea- 

 dow all have the same superficial meadow physiognomy. The Carex-Poa 

 meadow is separated from the other meadow vegetation types by the 

 abundance of Poa arctica, which is prominent when in flower, and by the 

 presence of a high lichen diversity. Carex-Poa meadow is best developed 

 in the drier parts of the polygonized sedge meadow complex where large, 

 flat, and sometimes slightly raised low-centered polygons with barely dis- 

 cernible troughs occur. The Carex-Poa meadow is also common on 

 hummocky rims of low-centered polygons in wetter areas and in areas 

 with pronounced polygon development. 



Carex-Oncophorus meadow (Type IV), the second most extensive 

 vegetation type, occupying 2\% of the map area, develops on moister 

 sites than the Carex-Poa meadow. It occurs on flat polygon centers and 

 in drained, shallow polygon troughs. It is distinguished from Carex-Poa 

 meadow on the basis of reduced lichen cover and the presence of mosses 

 such as Calliergon sarmentosum, Oncophorus wahlenbergii, and Aula- 

 comnium turgidum, and of Dupontia fisheri and Peltigera aphthosa. The 

 Carex-Oncophorus meadow has the greatest number of graminoid 

 species and was the vegetation type most intensively studied during the 

 Tundra Biome program. 



Dupontia meadow (Type V) occupies l^o of the mapped area. It is 

 characteristic of flat, slowly draining sites and wet polygon troughs. Eri- 

 ophorum russeolum is also common in this type, but the low cover of 

 Carex and the greater abundance of Dupontia and Eriophorum angusti- 

 folium distinguish it from the other meadow types. Woody dicotyledons 

 are essentially absent but several forbs occur. Cerastium Jenisejense, 

 Stellaria edwardsii and S. laeta may form distinctive mats, and Saxifraga 

 cernua is a common erect forb. 



The vegetation that composes the Carex-Eriophorum meadow 



