322 REINERS 



1965 rate until it reaches a limit of 10 X 10 9 people. This in no way is meant to 

 be a prediction for population. It simply terminates the model. 



Detritus-pool dynamics were computed according to this model by a 

 difference-equation procedure iterated every year until all parameters reached 

 limits dictated by the model. I wish to emphasize that Fig. 1 is not meant to 

 represent reality in a quantitative sense but only to portray some essential 

 features of pool dynamics and a possible pattern of change in this compartment 

 of the carbon cycle. We do not know the rates of change in either litterfall or 

 decay and can only guess at possible limits on input and output since these will 

 be products of a future, unpredictable civilization. It is a testimony to our 

 present state of knowledge of the carbon cycle that, of all the parameters in the 

 model, only initial detritus-pool size and litter input are based on data and that, 

 among these, pool-size estimates range from 700 to 9000 X 10 tons/year. 



Clearly, better measurements of pools and processes are required to 

 construct a realistic model for the carbon cycle. 



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