31 



A proper mixture of species and subsequent thinning will give a 

 shelter belt which is both rapid growing and long-lived. The mix- 

 ture should consist of a fast-growing, light-demanding species for 



6' 



P P P 



Fig. 2. Diagram of pare and mixed plantations. 



the temporary tree ; and a slower-growing, shade-enduring species 

 for the permanent tree. These requirements are met by a mixture 

 of silver maple and sugar maple. The trees should be planted 7 feet 

 apart and in squares. In the following diagram, which 'shows the 



[Cir. 81] 



