260 F. L. Bunnell et al. 



should not significantly modify the soil environment. However, where 

 compaction by traffic impeded aeration and mixed plant and soil mate- 

 rials, sulfide evolution was evident and associated with rates of soil res- 

 piration four to six times greater than in adjacent, undisturbed areas. In 

 such areas, the environment was likely made less favorable for vascular 

 plant nutrition. 



Iron bacteria are rarely found in tundra. In their review of Interna- 

 tional Tundra Biome research sites, Dunican and Rosswall (1974) re- 

 ported iron bacteria only from Hardangervidda, a Norwegian subarctic 

 site where they were abundant at only one sampling location. The high 

 concentrations of iron in ponds and soils at Barrow certainly provide 

 potential habitats for iron bacteria. Despite the availability of substrate, 

 chemoautotrophs that can oxidize ferrous iron were not detected, 

 although several heterotrophic species, which incorporate ferric iron into 

 their cell envelopes, were isolated from surface soils. 



In general, the available taxonomic information for tundra bacteria 

 suggests that they have more limited diversity than bacterial flora from 

 soils of temperate regions. However, there appear to be at least some 

 bacterial species present that are capable of decomposing or mineralizing 

 most of the major organic and inorganic substrates. Under laboratory 

 conditions, at temperatures of to 5 °C, many pure cultures of both tun- 

 dra bacteria and fungi are capable of rapid metabolism. Experimental 

 studies such as those with heated soils or sulfate enrichment demonstrate 

 that in situ decomposition can increase dramatically under some field 

 conditions (Benoit, pers. comm.). Together these observations suggest 

 that existing rates of decomposition in tundra soils cannot be attributed 

 to the absence of specific organisms. 



Fungi and Yeasts 



As with bacteria, the number of species of fungi in tundra is consid- 

 erably less than in other Biomes, with the possible exception of the 

 Desert Biome (Laursen 1975, Laursen and Miller 1977). Nevertheless the 

 major classes of fungi are represented at Barrow. Proportions of Bas- 

 idiomycetes in sterile hyphal counts with clamp connections generally 

 range from 5 to 50%. Among the fungi in the vegetative, litter and soil 

 layers, the sterile forms and/or Basidiomycetes not revealing clamp con- 

 nections also show the greatest species diversity; the Fungi Imperfecti are 

 next, followed by the Ascomycetes, including yeasts. In the relatively wet 

 areas, including the ponds, there is a diverse and at times abundant flora 

 of aquatic fungi. 



Few endemics are present and the specific characteristics of the my- 

 coflora lie in the relative importance of a given species or in the rarity of 



