TOTAL YIELD OF PHOTOSYNTHESIS ON E.\RTH 7 



multiplied by their area (361 X lO*' sq. km.) and corrected for 15% 

 respiration losses, the result is 15.5 X 10^° tons, or eight times the yield 

 of carlion fixation on land as calculated by Schroeder! Even a deduction 

 of 10 or 20% for the Polar Sea, and generally less fertile waters, would 

 not change this result significantly. Thus, the most probable value of 

 the rate of carbon fixation on earth is 15-20 X 10^° tons annually, with 

 at least four-fifths (and perhaps nine-tenths) of this amount contributed 

 by the oceans. 



Table l.III 



It is interesting to compare this rate of carbon transformation by the 

 plants with the total quantity of carbon available on earth. Table LlV 



T.\BLE l.IV 

 Carbon Reserves of the Earth 



Region of earth or atmosphere 



Total amount 

 of carbon, tons 



Lithosphei-e (earth's crust 16 km. deep) 

 Hj'drosphere (oceans and seas) 

 Troposphere (air up to 11 km. height) 



2-8 X 10'6 



5 X 10" 



6 X lO'i 



lists some geochemical data (cf., for example, Vernadsky 1930). The 

 large amount of carbon in the carbonate rocks is almost unavailal)le to 

 the plants. The large reservoir of dissolved carbonates and bicarbonates, 

 on the other hand, is fully available to aquatic plants, and stands in a 

 continuous exchange with the gaseous carlion dioxide in the atmosphere, 

 thus helping to maintain the concentration of the latter on a constant 

 level, and contributing indirectly to the food supply of land plants. Ac- 

 cording to the figures given in Table l.III, the land plants assimilate a 

 quantity of carbon equivalent to the total amount of carbon dioxide in 

 the air above the continents, in less than ten years. An approximate 

 confirmation of this estimate Avas provided by (Jut (1938). who measured 

 the carbon dioxide concentration of the air at different heights above a 

 pine forest and calculated that each day the trees consume all carbon 

 dioxide from an air column 50 meters high. Since the atmosphere corre- 



