18000 



MGMT 



PCA 

 PCI 



PCB 

 000 

 POO 



3000 



Figure 25 — Effect of thinning on total yield of Douglas-fir plantations (total cubic 

 feet), site index 90. 



25000 



MGMT 



000 

 POO 



PCB 



PCI 

 PCA 



10 ao 30 40 50 60 70 80 90 100 110 120 130 140 150 



AGE 



Figure 26 — Effect of thinning on total yield of Douglas-fir plantations (merchantable 

 board feet [Scribner]), site index 50. 



23 



