270 



F. L. Bunnell et al. 



TABLE 8-2 



Patterns of Bacterial Biomass with Depth 

 and Time as Estimated by Plate and Direct 

 Counts from Soils in Wet Meadows for 

 1971 



corrected for bulk density, basins and rims of low-centered polygons still 

 support the least bacterial biomass while polygon troughs and wet mea- 

 dows support significantly more (Table 8-1). 



The plate to direct count ratios observed for soil bacteria in the 

 Biome research area commonly range from 1 : 1000 to 1 :8000 in the upper 

 2 cm and become somewhat broader with depth (Table 8-2). These values 

 are higher than many reported by Parinkina (1974) for tundra soils but 

 do not exceed the range she reported.- Parinkina also noted that com- 

 parison of data from amended soils of the tundra region and from soils 

 of temperate and southern regions shows that the difference between 

 direct and plate counts decreases both with cuhivation and decreasing 

 latitude. Two explanations for these trends may be offered. First, the 

 trends may testify to greater availability of nutrients in cultivated or 

 southern soils; second, they may document higher rates of decomposi- 

 tion and a smaller content of dead cells in those soils. 



Seasonal averages of the plate counts for yeasts in the upper 1 to 2 

 cm of soil range from 4.5 x 10' colonies (gdw soil)"' in basins to 2.7 x 10' 

 colonies (gdw soil)"' in rims of low-centered polygons (Table 8-1). The 

 technique used for isolation of yeasts probably cultures a limited portion 



