The Microflora 267 



Meadows 



Basins 



Troughs 



Rims 



Standing Dead ■-[ 

 Litter plus Moss "^ 



nmiwiinnnnii/iimi ' 



Soil z 



3 



(cm depth) 4 



5 



6 



7 



..algae . 



"■ fung 



3 



ii»i/)//niffiiii/!iin»mi?)iiiiiimi 



;? 



bacteria 



:i 



yjffm? 



Biomass, g ni" cm 



"■ 1 1 r 



10 1 2 



FIGURE 8-4. Depth profiles of the average biomass of algae and fungi in 

 1973 and bacteria (direct count) in 1971. Direct counts for bacteria are 

 only available for wet meadows. (Benoit, Cameron, Flanagan, Knox, 

 Miller and Webber, unpubl., and Laursen 1975.) 



both. Green filamentous forms dominate in polygon troughs (25*^0 of the 

 species present); green coccoids are particularly dominant, in terms of 

 number of species represented, in basins of low-centered polygons; and 

 euglenoids are totally missing from troughs (Figure 8-3). 



Even the relatively cosmopolitan algae differ in species composition 

 among the microtopographic units considered. These differences are 

 more marked among the soil fungi, which exhibit considerable taxono- 

 mic specificity (Figure 8-1) as well as broad trophic differences (Figure 

 8-2) among these units. 



Differences in taxonomic structure are associated with differences in 

 biomass. Among the algae the number of species represented and total 

 biomass show positive correlations among microtopographic units (cf. 

 Figure 8-3 and Figure 8-4). The most precise data available, however, are 

 those for the soil fungi. When all samples of fungal biomass from 1 to 2 

 cm depth collected during the summer of 1973 are subjected to two-way 

 analysis of variance, significant differences are found among microtopo- 

 graphic units for biomass levels of the soil-inhabiting mycelia. Recog- 

 nition of different fungal habitats is justified on the basis of broad tro- 

 phic differences and average biomass levels. 



Functional Implications of Taxonomic Structure 



Although the influences of an extreme environment are evident in 

 the reduced diversity, the capacity to degrade all major organic and inor- 

 ganic substrates is present (see also Chapter 9). The im.pact of low tem- 

 peratures and the rigorous freeze-thaw cycle is evident in the relative 

 sparsity of such taxa as Bacillus and common groups among the Mucor- 

 ales. The influence of substrate is most evident in the marked reduction 



