722 A NATIONAL PLAN FOR AMERICAN FORESTRY 



the tourist will find it most convenient to park his car, build his fire, 

 and do his walking where any damage that may result will be at a 

 minimum. In such special cases as the giant sequoia parks of Cali- 

 fornia, special measures are taken to protect the soil from the com- 

 pacting that would otherwise ultimately result in the death of the 

 absorbing roots and kill the trees. The fundamentals of tree physi- 

 ology and root parasitism need further study before the best procedure 

 can be outlined for the different situations that are encountered. In 

 forests in which both timber production and recreation are important, 

 a balanced program of preventive practices needs to be worked out 

 with consideration of both kinds of use. 



No disease-control measures are known to have been applied in 

 forests maintained purely for watershed protection, except in the 

 course of the white pine blister rust work in the Northeast, and no 

 other disease is known at the present time to justify direct control 

 activity in such forests. 



