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



synthetic view of decomposition. Tools of integration include correlative 

 analyses and computer simulation models. Although these tools are in 

 some instances novel and sophisticated, the conceptual framework 

 employed owes much to the seminal work of Douglas and Tedrow (1959) 

 (see Bunnell and Tait 1974). 



The approach in the following discussion moves through the con- 

 ceptual framework as it is presented above, first examining the potential 

 to exploit particular substrates that different microfloral constituents 

 possess. Then we examine the manner in which this potential and other 

 critical activities such as respiration are influenced by environmental var- 

 iables such as temperature, moisture and oxygen. The discussion in the 

 section on Decomposer activities and decomposition utilizes simulation 

 models to combine the responses of microbial respiration to individual 

 environmental variables and compares the predictions with integrative 

 measures such as weight loss. Measures of microbial biomass, yield and 

 efficiency are related to substrate availability and potentials for mineral 

 cycling and immobilization. 



POTENTIAL OF THE MICROFLORA 

 TO UTILIZE SUBSTRATES 



The decomposition of organic remains proceeds mainly through the 

 action of microorganisms that can use them as a source of energy and 

 nutrients. Most soil microbial populations are heterotrophic and the or- 

 ganisms compete for available substrates. In the coastal tundra at Bar- 

 row, microbial saprophytes are more competitive and abundant than are 

 parasites and the present discussion ignores the latter. Not all sapro- 

 phytic microorganisms utilize and compete for the same substrates. 

 Although an individual microorganism may be encouraged by the pres- 

 ence of a specific substrate that it can use, its potential to exploit that 

 substrate is further modified by environmental conditions and "competi- 

 tive saprophytic ability" (Garrett 1963). The composition of the micro- 

 bial population inhabiting a particular substrate and thus the decomposi- 

 tion rate of the substrate are therefore dependent upon the environ- 

 mental conditions and competitive ability of the microorganisms as well 

 as the measured potential to utilize specific substrates. The data pre- 

 sented here are based almost entirely on in vitro measurements. The dis- 

 cussion is biased towards treatment of the mycoflora rather than of the 

 total microbial population. 



Major substrates for decomposer organisms at Barrow can be divid- 

 ed into two main categories on the basis of their chemical composition, 

 pattern of dissolution and utilization by microorganisms. These categor- 

 ies are 1) low molecular weight, water- and/or 80%-ethanol-soluble frac- 



