342 BOTKIN, JANAK, AND WALLIS 



mately 50% above normal, changes in the structure or productivity of the forest 

 as measured by basal area would probably not be observable. Changes in net 

 forest productivity would occur at this or higher levels for early stages in 

 succession. The major long-term effects of such extreme fertilization would be 

 on the standing crop, and this change is much less than that which a linear 

 extrapolation would suggest. A 100% increase in the annual growth rate of every 

 tree for every year produces a standing crop increase of approximately 40%. 



The important and unexpected effect of such fertilization is to weight the 

 environment in favor of shade-tolerant, long-lived species and against shade- 

 intolerant, short-lived ones. As a result, the process of succession is hastened. 

 However, the final relative importance of each species is changed only to a small 

 degree. 



We find these results reasonable yet intriguing. They point out the need for 

 better data regarding the fundamental population characteristics of major tree 

 species. Probably of most significance, the simulator suggests ways in which a 

 community of interacting species has characteristics different in kind from 

 carefully controlled and manipulated monocultures. 



ACKNOWLEDGMENTS 



This work was partially supported by grants from the Office of Water 

 Resources Research and the National Science Foundation. This is contribution 

 No. 37 of the Hubbard Brook Ecosystem Study. 



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