Microflora Activities and Decomposition 329 



TABLE 9-5. Standing Crops and Annual Weight Loss of Five 

 Organic Matter Pools 



'Average values from data collected over 4 years at three sites. 



'The losses are due primarily to the downward translocation of materials to roots in fall 



and to leaching in spring by meitwater. 



'Estimated from decay rates of roots and cellulose paper in litter bags inserted in the soil, 



1972-1977 (inclusive). 



lated maintenance demands are 0.0166 g m~^ hr"' or approximately 48 g 

 m"^ for the period of microbial activity, which is about 100 days. 



The annual primary productivity of the Carex-Oncophorus meadow 

 both above and below ground, including phanerogams and cryptogams, 

 is estimated to be approximately 200 g m"^ If 48 g of organic matter m"^ 

 yr"' is necessary to maintain the average standing crop of microorgan- 

 isms, 152 g m'^ yr"' remains to be removed by microbial and invertebrate 

 activity or organic matter will accumulate. 



Litter-bag estimates of annual rates of decomposition for major 

 substrates in the upper 7 cm of soil (Table 9-5) indicate that 222 g m"^ is 

 decomposed annually. This is approximately one-half the rate for an 

 ungrazed short-grass prairie (Van Dyne et al. 1978). Minimal annual 

 maintenance requirements of microbes (48 g m"^) and invertebrates (7 g 

 m"^ Chapter 1 1) could be met easily and would leave about 167 g m"^ an- 

 nually for production of microbial and invertebrate tissue. Ignoring in- 

 vertebrates, the potential number of microbial generations possible can 

 be estimated using the equation of Gray and Williams (1971): 



Yis + Nx) = Nx 



where s = total substrate available to microorganisms (total minus 

 maintenance) 

 TV = number of generations of average microbial biomass 

 Y and x are as in the two previous equations. 



Allowance is made for recycling of microbial tissue towards its own pro- 



