264 F. L. Bunnell et al. 



(1961) stated that desmids constitute about 75% of the freshwater algal 

 flora in the Arctic. Previous reviews of the arctic algal flora from fresh 

 water and soil suggest that both Prasiola spp. and Nostoc spp. contribute 

 importantly to the subaerial algal biomass or biomass in the surface soils 

 (Ross 1956, Taylor 1956). Nostoc commune was commonly encountered 

 in the field, although it was not common in culture. Prasiola spp. were 

 not collected from any of the sampled microtopographic units. However, 

 Prasiola spp. did form an observable cover over owl casts found in the 

 Biome research area (E.A. Schofield, pers. comm.) and Prasiola crispa 

 formed extensive green mats over caribou carcasses in the vicinity of 

 Prudhoe Bay (Atlas et al. 1976). 



Heterogeneity Within the Microflora 



Given the extreme variability of the soils of the coastal tundra both 

 laterally and with depth, dramatic changes in the taxonomic structure 

 and biomass of the microflora can be expected over lateral distances of a 

 meter and depths of a few centimeters. It is pertinent to document the 

 magnitude of this heterogeneity, and to determine the degree to which 

 the microflora constitutes groups that can be associated with specific mi- 

 crotopographic units. The variability in both taxonomic structure and 

 amounts of biomass is important. Taxonomic heterogeneity is evaluated 

 in the two broad groups for which the most taxonomic information is 

 available, higher fungi (Basidiomycetes and Discomycetes) and algae. 



Five microtopographic units are considered: wet meadows, polygon 

 troughs, the rims of low-centered polygons, basins, and the tops of high- 

 centered polygons. Beach ridges are treated together with the tops of 

 high-centered polygons because of the similarity of the resident vascular 

 plants and mosses present. Of the 33 fungal species collected, the highest 

 numbers are present in the relatively well aerated soils of polygon rims 

 and polygon tops (Figure 8-1). In contrast, fruiting higher fungi are 

 strongly reduced and often absent in basins of low-centered polygons. 

 Samples from basins revealed only three species (Aleuria aphanodictyon. 



Troughs (16),,..— -^^^^—^ i ms (16) 



FIGURE 8-1. The distribution of 

 numbers of species of higher fungi in four 

 microtopographic units. No fungal 

 species were restricted to the basins of 

 low-centered polygons. (Data of Laursen 

 Meadows (13) ^"~~^Tops(l9) and Miller.) 



