304 



REINERS 



TABLE 1 



ESTIMATED CARBON IN MAJOR COMPARTMENTS 

 OF THE BIOSPHERE* 



*Based on B. Bolin, The Carbon Cycle, Scientific American, 223: 124—132 

 (1970). 



Workers have modeled detritus pools as subsystems with inputs (litter) and 

 outputs (decomposition), each coming into balance when the detritus pool 

 reaches a steady-state level dictated by climate, soil, and organic factors. ' 

 Although there are some difficulties in the details of this view, 6 ' 7 it forms the 

 theoretical basis for numerous studies on specific dynamics in a wide variety of 

 ecosystem types. 



Output from detritus is principally to the atmosphere as C0 2 , where a large 

 fraction may be quickly fixed again by plants. 8 Some carbon is lost to the 

 atmosphere in such other gaseous forms as methane and ethanol, especially from 

 anaerobic sites, and some is lost to groundwater solution via carbonate 

 equilibrium reactions and as soluble organic acids, polyphenols, and various 

 other compounds. 1 Some of this organic carbon, reaching streams via 

 groundwater, overland flow, and erosion, is consumed by aquatic heterotrophs 

 in streams, 1 1 and the remainder enters marine systems. Dissolved inorganic 

 carbon may be released to the atmosphere when groundwater moves into surface 

 waters, or it may be fixed in various forms and carried to the oceans. 



To the extent that man is influencing terrestrial detritus pools through 

 cultivation, fertilization, erosion, fire, and lumbering, he is altering rates of 



