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A NATIONAL PLAN FOR AMERICAN FORESTRY 



TABLE 9. Number of trees, volume and growth in average stocked virgin stand oj 

 ponderosa pine in eastern Oregon 



1 No deduction has been made for tree mortality or losses from wood rotting fungi, etc. Net growth per 

 acre may be as great as 85 percent of amount shown or insect and other losses may entirely wipe out the 

 current growth in mature stands. 



Studies of the growth of ponderosa pine by Dr. Walter N. Meyer, 

 of the Pacific Northwest Forest Experiment Station (20\ have shown 

 that where sufficient growing stock is preserved after each cut the rate 

 of growth is fairly satisfactory. Where a stocking of 2,000 cubic feet 

 per acre is preserved 690 cubic feet is added to the volume in the next 

 30 years. Where a growing stock of only 200 cubic feet is preserved 

 only 220 cubic feet of growth is obtained in that period. These 

 results are from all-aged stands. 



In terms of saw timber 11.6 inches or more in diameter, a stocking of 

 10,000 board feet produces 4,000 board feet of added growth in 30 

 years, whereas a stocking of 1,000 board feet produces only 1,300 

 board feet in the same time. Owing to greater risk of insect attack 

 on older trees it may be undesirable to leave fully stocked stands after 

 the first cutting in virgin timber. If understocked stands are left the 

 growing stock should be built up with younger trees during further 

 management operations. 



It should be noted that while Meyer shows only 15 board feet per 

 year mortality loss in selectively cut stands, he cites Bureau of 

 Entomology studies made under the direction of F. P. Keen in virgin 

 stands in southern Oregon and northern California showing insect 

 losses amounting to from 103 to 1,082 board feet per acre per year in 

 1927, the year of heaviest recorded loss. On the 17,400 acres covered 



