Microflora Activities and Decomposition 325 



FIGURE 9-12. Cumulative COj release over a single 

 growing season, simulated for soil microbes, mi- 

 crobes plus roots and the whole system, and meas- 

 ured by KOH titrations in darkened lysimeters. Root 

 respiration includes that of microbes associated with 

 the rhizosphere. Whole-system CO2 evolution in- 

 cludes the flux from soil microbes, roots, above- 

 ground decomposers and respiration of aboveground 

 plant biomass. (After Bunnell and Scoullar 1975.) 



For the more advanced stages of decomposition, such as below- 

 ground substrates, the relationships of microbial activities to decomposi- 

 tion are not as well quantified. No data are available on the chemical 

 composition of belowground substrates. Furthermore, measures of mi- 

 crobial activity are confused by the activities of invertebrates and vascu- 

 lar plants. To evaluate the hypothesis concerning decomposition below 

 ground, a broader approach incorporating more ecosystem components 

 but less chemical detail has been employed. The model abisko ii (Bunnell 

 and Scoullar 1975) incorporates the temperature and moisture influences 

 expressed but also simulates contributions from dying roots and respira- 

 tion of vascular plants. 



Bunnell and Scoullar (1975) have evaluated the model abisko 11 for 

 the Biome research area comparing in situ measures of carbon dioxide 

 evolution with the cumulated totals of simulated respiration from rele- 

 vant components of the system (Figure 9-12). The whole-system respira- 

 tion of Figure 9-12 includes carbon dioxide evolution from soil microor- 

 ganisms, roots, aboveground decomposers, and the growth plus main- 

 tenance respiration of aboveground live material. 



Simulated microbial respiration follows a pattern very similar to 

 that of the field measures of respiration, but shows a greater depression 

 early in the season. The early season depression is most evident in the 



