The Vegetation: Pattern and Succession 191 



Webber et al. 1976) and other tundra studies (Gjaerevoll 1956, Bliss 

 1963, Scott and Billings 1964), snow cover does not emerge as a major 

 controlling factor from these analyses. The variations in microrelief 

 among most of the sampled locations are insufficient to produce a pro- 

 nounced variation in snow cover. However, where ravines, creek banks, 

 beach ridges and snow fences occur, snow cover becomes an important 

 factor influencing vegetation distribution. 



Vegetation Turnover Patterns 



As discussed in Chapter 1 (Table 1-4), eight major vegetation types 

 or noda were distinguished in the vegetation of the coastal tundra at Bar- 

 row. Most species occur in more than one vegetation type, but the types 

 are distinguished by the presence of certain indicator species and the con- 

 sistent importance of other species. Each vegetation type has a reason- 

 ably distinct standing crop composition at the period of peak above- 

 ground biomass (Table 3-2). The Cochlearia meadow is a rudimentary 

 vegetation restricted to recent alluvium and disturbed sites; it is therefore 

 not included in the discussion. 



Each vegetation type has a unique distribution within the three axes 

 of the ordination (Figure 6-4). The vegetation types are numbered from 

 Luzula heaths to Arctophila pond margins, following the primary con- 

 trolling gradient of increasing soil moisture which is associated with in- 

 creasing snow cover. Along a gradient of increasing hydrogen sulfide, 

 the sequence of vegetation types is from Luzula heath, Salix heath, and 

 Carex-Poa meadow, all found on well-drained sites, to Carex and Du- 

 pontia meadows, Arctophila pond margin, and Carex-Oncophorus mea- 

 dow, all found on poorly drained sites with still or stagnant water. Along 



moisture 



H/ LO soluble phosphate hi lo 



moisture 



HI 



FIGURE 6-4. The distribution of seven mature vegetation types within 

 the ordination. I) Luzula heath, II) Salix heath. III) Carex-Poa meadow, 

 /K> Carex-Oncophorus mead/ow, V)Y)\ix>oni\3. meadow, K/y Carex-Erio- 

 phorum meadow, VII) Arctophila pond margin. (From Webber 1978.) 



