Microflora Activities and Decomposition 321 



Several important points emerge from their analyses. The coefficients 

 associated with the volatile and lignin components were occasionally neg- 

 ative, implying negative respiration. Analyses yielding negative coeffici- 

 ents for respiration usually had a disproportionately large number of 

 Dryas substrates. The observations imply 1) that respiration rates of total 

 substrates from any botanical taxon cannot be predicted consistently 

 from independent consideration of the five substrate components men- 

 tioned above, and 2) that some substrate components may have an inhib- 

 itory effect on the respiration rate of other components. 



In addition to generating inhibitory effects, specific substrate com- 

 ponents also may provide energy for the degradation of more recalcitrant 

 components. For example, the observed rates of weight loss from pure 

 cellulose filter papers placed in the field are lower than rates of loss of 

 cellulose from natural substrates. 



As well as indicating the failure of the five selected chemical constit- 

 uents to contribute independently to microbial respiration, the analyses 

 of Bunnell et al. (1977b) indicate that the predictabihty of regression 

 equations within temperature-moisture classes is little altered by ignor- 

 ing amounts of pectin, starch and volatiles in the substrate being re- 

 spired. When broader chemical groups (e.g. percent ethanol-soluble and 

 percent ethanol-insoluble) are employed, and Dryas substrates are omit- 

 ted, regression coefficients for the two substrate components are consis- 

 tently different and significantly greater than (a < 0.(X)1). Rates of 

 respiration of ethanol-soluble components are about 5 to 10 times 

 greater, depending on temperature, than the rates associated with other 

 chemical constituents. It is noteworthy that ethanol-soluble compounds 

 make a greater contribution to total respiration at higher temperatures. 



The discussion of microfioral potential to utilize substrates noted 

 that several fungal isolates show higher temperature optima for utiUz- 

 ation of substances of lower molecular weight than they do for utiliza- 

 tion of the more recalcitrant substances such as cellulose. The analyses 

 associated with the last equation suggest that the phenomenon is general 

 within the mycoflora of the coastal tundra at Barrow and applies to asso- 

 ciated rates of respiration as well as to the physiological potential to de- 

 grade these substrates (Bunnell et al. 1977b). At lower temperatures tun- 

 dra fungi not only maintain their competence to degrade more recalci- 

 trant chemical constituents (Figure 9-1), but also have a greater propor- 

 tion of their respiration associated with these constituents. 



Microbial Respiration as a Measure of Weight Loss 



Implicit in the preceding discussion is the assumption that the gener- 

 al form of the response surface for microbial respiration against temper- 



