344 BOTKIN, JANAK, AND WALLIS 



photosynthesis to C0 2 is anywhere from 50 to 100% as great as increase in 

 percentage ambient C0 2 . Such response was measured in September, May, and 

 June for shoots in the canopy, below the canopy, and on seedlings on days 

 ranging from full light to 25% full light. Response to C0 2 enhancement in 

 increments, up to a maximum concentration of over 500 ppM, appears linear to 

 400 ppM and curvilinear to 500 ppM. Relative responses of different species 

 varied considerably, with oaks advantaged more than pine. 



