296 P. W. Flanagan and F. L. Bunnell 



TABLE 9-1 Percentage of 



Bacterial Types at 

 Barrow Capable of 

 Utilizing Specific 

 Carbon Sources 



Note: Based on 200 randomly selected aer- 

 obic types isolated from the 0- to 2-cm soil 

 depth in wet meadows and tested at 15 °C. 

 Source: Benoit (unpubl.)- 



matic ring of humic materials require the presence of oxygen. Thus, as 

 humic materials move from the surface into the less aerobic subsurface 

 layers of the soils, the probability of their decomposition is markedly 

 reduced. The differential capacities of bacteria and fungi to survive low 

 amounts of oxygen and to exploit humic material are instrumental in the 

 accumulation of organic matter in the soil horizon. 



The strictly anaerobic portion of the microflora remains the least 

 known in terms of physiology and in situ activity. Rapid development 

 and intense activity of anaerobes on the soil plots heated to 15 to 20 °C il- 

 lustrates the potential of this group. Enrichment cultures of strictly an- 

 aerobic cellulose-decomposers and methane-producers were obtained 

 from anaerobic soils on these plots. There is no evidence that anaerobic 

 bacteria can degrade humic materials; therefore the activity of the anaer- 

 obes becomes limited when the pool of rapidly decomposable material 

 originating from the death of belowground parts is exhausted. Contin- 

 ued decomposition requires the action of other microorganisms and a 

 change of abiotic conditions. 



