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



duction at a rate governed also by the yield coefficient Y, in the term 

 Y(Nx). Solving for N, the total number of average microbial standing 

 crops possible per year, gives 5.0 and 4.3 generations based on measures 

 of total decay and primary production respectively. Observed rates of 

 turnover for fungi in Carex-Oncophorus meadows were markedly lower, 

 1.5 to 3.3 times, varying with depth (Table 8-3). In the troughs, however, 

 observed turnover rates were similar to those calculated, 3.6 to 6.2 times, 

 but fungal biomass was significantly lower. Only in the most productive 

 areas do fungi exhibit values comparable to calculations based on labora- 

 tory measurements. In these areas the accumulation of organic matter is 

 lowest (Chapter 7). The observation that litter bags in meadows estimate 

 an annual rate of decomposition greater than annual input from primary 

 production may result from overestimation of the decay rates of untested 

 but apparently more recalcitrant material at depth. The observations do 

 suggest that in the most favorable microhabitats decomposition can ap- 

 proximate primary production. Douglas and Tedrow (1959) observed 

 similar variability in rates of decomposition of organic matter from tun- 

 dra soils. Highest rates of decomposition were observed from the half- 

 bog soil (Dupontia meadows and polygon troughs, Table 1-4). Those 

 rates, 190 g m■^ are comparable to the most rapid rates we have esti- 

 mated and again suggest no accumulation of organic matter in sites most 

 favorable for decomposition. 



If all 222 g m"^ yr"' of decomposable tissue undergoes dissolution to 

 carbon dioxide, water and minerals through microbial processes, then, 

 based on an average carbon content of 0.45 g g"' organic matter, decom- 

 posers should release carbon dioxide to the atmosphere at an average rate 

 of about 152 mg m'^ hr"'. If annual primary production is matched by 

 decomposition the estimate of average carbon dioxide evolution is 144 

 mg m"^ hr"'. 



Root and Microbial Respiration 



The annual weight loss from belowground substrates plus surface 

 litter is about 190 g m"^ yr"' (Table 9-5). If all of this matter, or an equiv- 

 alent amount minus the average standing crop of microbial biomass 

 below ground (190-17.5 = 172.5 g m"^ yr"'), is consumed annually by 

 microbial metabolism, maintenance and growth, it is possible to calcu- 

 late an average release of CO2 m"^ hr"' from Barrow soils that does not 

 include the CO2 emission of roots. 



The average carbon concentration of the soil organic matter in the 

 top 10 cm is about 45% so 172.5 g of organic matter could release 78 g C 

 or 286 g CO2. The amount of carbon dioxide released annually (100 days) 

 by microbes would be equivalent to an average respiration rate of 1 19 mg 

 CO2 m"^ hr-'. 



