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



and Williams 1971). These aspects of microbial activities are best related 

 to inputs from primary production. 



Under aerobic conditions, microbes decomposing a substrate break 

 down complex organic molecules to end-products that are primarily inor- 

 ganic (carbon dioxide, water and minerals); under anaerobic conditions 

 the end-products assume a variety of organic and inorganic forms. The 

 breaking down is accompanied by a loss in weight and energy content of 

 the substrate as well as disintegration of its physical structure. An ob- 

 server of the decomposition phenomenon thus witnesses physical and 

 chemical as well as biological changes. Measures of decomposition incor- 

 porate varying features of these changes, and no one measure quantifies 

 decomposition perfectly. Belowground events are especially difficult to 

 decipher because of the simultaneous respiration of heterotrophic and 

 autotrophic organisms and the complex geometry of hundreds of sub- 

 strates and microorganisms showing vastly different responses. Soils of 

 the coastal tundra at Barrow are frozen for a large part of the year and 

 this further complicates examination of biological processes within them. 



Given the complex of physical, chemical and biological processes 

 comprised in decomposition, diverse methods have been employed to re- 

 late the findings of individual, specialized techniques to general con- 

 cepts. The concepts of decomposition used recognize that different mi- 

 crobes have different enzymatic potentials or capacities to utilize various 

 chemical constituents of naturally occurring substrates. Not only do 

 microbes have different capacities to exploit substrates, but their enzym- 

 atic potential, growth and respiration rates also respond differently to 

 the temperature, moisture, oxygen and pH in their environment. Thus 

 the capacity to decompose inherent in a particular microbial population 

 is at any time modified by the environment. 



Acknowledging this conceptual framework, our studies of decom- 

 position have examined the physiological potentials of different micro- 

 floral constituents to utilize particular chemical compounds as sub- 

 strates; the response of these potentials to environmental conditions; the 

 biomass, biomass yield per gram of substrate, and maintenance demands 

 of major microbial species; the response of rates of respiration and 

 growth to changes in important environmental variables such as temper- 

 ature, moisture, oxygen and dissolved nutrients; and the resultant loss 

 rates of particular chemical constituents, carbon, calories and net 

 weight. Measures of ability to utilize particular chemical compounds are 

 in vitro assessments of an organism's ability to exploit selected natural 

 substrates. Responses of respiration and growth to selected environ- 

 mental variables and measures of biomass yields and maintenance 

 demands are also evaluated, primarily by laboratory techniques, par- 

 ticularly Gilson respirometry. Laboratory measures are related to field 

 observations by simulation models (Flanagan and Bunnell 1976, Bunnell 



