SHORTLEAP PINE: IMPORTANCE AND MANAGEMENT. 37 



Table 19. — Trees per acre in unthinned and thinned stands of various ages. 1 



Age. 



Trees per acre. 



Age. 



Trees per acre. 



Better situations. 



Poorer situations. 



Better situations. 



Poorer situations. 



Un- 

 thinned 

 stands. 



After 

 thin- 

 ning. 



Un- 

 thinned 

 stands. 



After 

 thin- 

 ning. 



Un- 

 thinned 

 stands. 



After 

 thin- 

 ning. 



Un- 

 thinned 

 stands. 



After 

 thin- 

 ning. 



Years. 

 20 



Number. 

 1,400 

 680 

 480 

 340 

 270 



Number. 

 990 

 525 

 380 

 280 

 230 



Number. 

 2,120 

 990 

 680 

 460 

 340 



Number. 

 1,460 

 820 

 540 

 380 

 290 



Years. 

 70 



Number. 

 225 

 200 

 185 

 175 



Number. 

 195 

 175 

 165 

 160 



Number. 

 260 

 200 

 185 

 180 



Number. 

 230 

 190 

 180 

 175 



30 



80 .. 



40 



90 



50 



100 



60 







1 Represents about an average number based on measurements in 128 well-stocked stands in various 

 portions of the range. 



TREES TO BE REMOVED. 



For convenience in thinning, trees may be divided into four groups 

 of " dominant," " codominant," " intermediate," and " suppressed." 

 These groups are termed " crown classes," and represent the relative 

 importance of the trees in the composition of the stand. The domi- 

 nant and codominant trees compose the bulk of the stand, forming 

 the general level of the forest canopy. They receive full light from 

 overhead, and the dominant ones some from the sides also. The co- 

 dominant trees are somewhat crowded on the sides. The intermedi- 

 ate trees have smaller crowns and are generally below the main 

 level of the stand, where they receive only a small amount of light 

 from above. They clearly belong to the class of trees which is be- 

 ing gradually crowded out. The suppressed trees are the smaller 

 sickly ones completely below the general forest canopy. 



Athough there are certain more or less essential rules for thinning 

 average shortleaf pine stands, they will not fit all cases, and the removal 

 of the trees is largely a matter of individual judgment. In general, 

 thinnings should be made primarily for the better development of 

 the dominant and codominant classes. This is accomplished through 

 the removal of the more crowded intermediate and suppressed trees 

 on the lower side and the exceptionally large, overshading or " wolf " 

 trees on the upper side. In the crowded groups it is often necessary 

 to remove as many as one-half, or occasionally two-thirds, of the 

 intermediate trees, together with a few trees of the codominant class. 

 Figure 3 represents an overstocked 30-year-old shortleaf stand and 

 several subsequent thinnings. In ordinary early thinnings the num- 

 ber of trees removed is about one-third of the total stand. The sup- 

 pressed trees are making exceedingly small growth and exert no ap- 

 preciable influence upon tin; stand. Their removal, however, is 

 beneficial in decreasing the fire menace. Large openings should al- 



