WESTERN YELLOW PINE IN OREGON. 



27 



Table 11. — Average merdiantahle volume in hoard feet of yellow-pine trees at various 

 ages for 10 typical localities in Oregon. 



Age, 

 years. 



Whit- 

 ney and 

 Austin. 



Look- 

 ing- 

 glass 

 Creek. 



Wia- 

 lock's 

 MiU. 



Ochoco 

 Creek. 



Sisters 

 (1). 



Lapine 

 (1). 



Fort 

 Kla- 

 math. 



Odessa. 



Mead- 

 ow 

 Lake. 



Em- 

 body. 



Aver- 

 age. I 



Volume of tree, in board feet. 



20 

 40 

 60 

 80 

 100 

 120 

 140 

 160 

 180 

 200 

 220 

 ^0 

 260 

 280 

 300 

 320 

 340 

 360 

 380 

 400 

 420 

 440 

 460 

 480 

 500 

 1 































































20 



50 



95 



160 



250 



360 



490 



630 



780 



920 



1,050 



1,170 



1,290 



1,400 



1,510 



1,610 



1,700 



1,790 



1,870 



1,940 



2,010 



2,080 



2.150 



10 



115 



180 



250 



320 



400 



480 



570 



670 



770 



880 



990 



1,110 



1,230 



1,340 



1,440 



1,540 



1,640 



1,730 



1,820 



55 



92 



140 



172 



279 



407 



644 



688 



835 



982 



1,130 



1,279 



1,430 



1,431 



1,564 



1,702 



1,838 



1,955 



2,017 



2,123 



2,155 



2,240 



2,322 















80 



230 



400 



600 



800 



1,000 



1,190 



1,370 



1,550 



1,730 



1,910 



2,090 



2,260 



2,430 



2,600 



2,770 



2,940 



20 



90 



180 



300 



440 



580 



710 



830 



950 



1,060 



1,170 



1,280 



1,380 



1,480 



1,580 



1, 680 



1,770 



50 



150 



205 



275 



350 



430 



510 



690 



670 



750 



835 



925 



1,020 



1,110 



1,210 



1.300 



1.390 



1.480 



1.570 



1.660 



1,750 



150 



260 



380 



500 



605 



705 



810 



935 



1,070 



1,230 



1,430 







20 



105 



195 



290 



390 



500 



610 



730 



860 



980 



1.110 



1,240 



1,370 



1,500 



1,600 



1,790 



1,930 



2,070 



2,210 



2,350 



2,490 



80 



210 



370 



540 



730 



920 



1,110 



1,300 



1,480 



1,660 



1,820 



1,980 



2,120 



2,260 



2,400 



2,540 



2,680 



2,820 



2,960 



20 



75 



140 



205 



280 



365 



470 



590 



740 



900 



1,090 



1,270 



70 



165 



265 



375 



480 



600 



720 



840 



960 



1,070 



1,170 



1,260 



1,320 



1,370 



1,420 



1,450 



1,470 



1,490 



1,500 



1,510 























































I The average of 20 separate stands ia Oregon, the data for only 10 of which are given in the above table. 

 FACTORS AFFECTING GROWTH. 



The most important single factor that affects growth is the amount 

 of available soil moisture. Provided that climate and drainage are 

 satisfactory, the most rapid growth is found in well-watered situa- 

 tions — ^in coves, on moist north and south slopes, and on benches. 

 Heat also tends to promote the vigor of growth, provided soil and 

 moisture conditions are satisfactory; hence at the higher, colder ele- 

 vations and in cold situations growth is slower. 



Another factor which materially affects the rate of growth of indi- 

 vidual trees is the density of the stand. In the study of the crown 

 space needed by trees of various sizes (see Table 6) it was found that 

 trees make their maximum growth when they have more space than 

 they do in the average virgin forest, open as it is. Beyond a certain 

 point increase in available crown space apparently does not cause an 

 increase in the growth rate. In some situations an excess of room 

 seems to inhibit growth, perhaps because it subjects the tree to 

 excessive exposure to wind and evaporation. It is natural to expect 

 that selection cuttings such as are practiced on the National Forests 

 (described in the chapter on "Management") will stimulate the 

 reserved trees to more rapid growth, and such is found to be the case. 



In a detailed study* of several areas in the Blue Mountains, partially 

 logged over several years ago, the increase in the basal area growth of 



1 Manu-script reiwrt by K. II. Weitknecht, a,Sii,stant forest ranger. 



