APPENDIX 379 



TABLE 2 



SUBDIVISION OF ORGANIC CARBON INTO 

 MATERIALS WITH SHORT OR LONG RESIDENCE 



TIMES 



*Mean residence of carbon in the atmosphere: 8.8 years. 

 Note: The numbers shown here are not data but intelligent 

 guesses of the way the estimates from Table 1 can be subdivided. 

 Definitions of "short" and "long" residence times are given in 

 the text. 



comparison with estimates of change in decay rates perpetrated by man. 

 Man-caused changes in decay rates are generally in a positive direction and are 

 effected through drainage, tilling, fertilization, burning, and erosion. Because of 

 their variation in type and intensity in space, it will be extremely difficult to 

 produce worldwide net estimates, not to mention the difficulties in measure- 

 ment itself. Nevertheless, a thorough examination of many fields of literature 

 would produce more information on the subject than we now have — which is 

 virtually none — and the most useful field operations would undoubtedly 

 become plainer as such a review and analysis proceeded. 



Influences of Land Use on Biotnass 



The lack of certainty of man's effects on biomass was a major source of 

 discussion at the Brookhaven Symposium. Whittaker and Likens and several 

 others felt that forest harvesting at frequent intervals, conversion of forests to 

 agriculture, and general toxification of environment must all be causing an 

 accelerating decrease in world biomass and thus a decrease in the size of the 

 pool. Others maintained that the effect of forest harvesting results in increased 

 rates of carbon uptake through higher rates of biomass accumulation, thus 

 mitigating higher C0 2 levels in the atmosphere. This dichotomy presents a 

 challenge to a true evaluation of man's impact on the biota. If, indeed, biomass 

 is declining, the rate at which it is declining should be of vital concern. 



