LOBLOLLY OR NORTH CAROLINA PINE. 161 



sufficient density should be maintained to prevent the development of 

 limbs which would make knots of this size on the lower three logs on 

 Quality I and the lower two logs on Qualities II and III. The sup- 

 pressed trees need not be removed. They make small demand upon soil 

 moisture, yet serve a very useful purpose on account of their low crowns 

 in. shading the soil and lessening drying winds. This is particularly 

 applicable to very dry clay sites; less so to very sandy sites. When 

 the mature stand is fully developed, it can be removed in one cutting 

 or in several cuttings made at short intervals. 



Notwithstanding that the pure even-aged stands of loblolly pine offer 

 unexcelled inducements for thinnings made for the purpose of acceler- 

 ating the growth of the individual tree, no adequate data are available, 

 either as the result of experience in commercial forests or in experi- 

 mental plots which show the preferable manner in which thinnings 

 should be executed, their cost or their effects upon the yield of the stand. 

 It is believed that by proper thinning the rate of diameter growth of 

 all trees in a stand can be stimulated well beyond that given in Table 71 

 for dominant trees. There would not be as many trees per acre on such 

 thinned stands as there are in the dominant class of crowded stands 

 (Table 42), but the larger volume per tree and the larger amount of 

 saw timber would more than compensate for the smaller number of 

 trees. A stand containing 6,000 cubic feet per acre in 60 trees, each of 

 which will yield 560 board feet (Tables 19 and 21) or 36,000 feet per 

 acre is far more valuable than one containing 6,000 cubic feet formed 

 of 100 trees, each containing 300 board feet and yielding 31,000 feet per 

 acre. Not only .is the cost of operation less, there being 50 per cent 

 more logs to handle in the stand containing the larger number of trees, 

 but in addition to the larger yield per acre the stumpage of the larger 

 trees is intrinsically more valuable per unit on account of the larger 

 proportion of wide stock and high grades it will yield. (Pages 119 

 to 127.) 



It is possible however to determine approximately the results upon 

 yield of very intensive thinnings by means of data obtained from fully 

 stocked unthinned stands. Certain trees in such stands on account of 

 the fact that they are less crowded and have more growing space have 

 outstripped all others both in height and diameter. These are the pre- 

 dominant trees which constitute in the normal unthinned fully stocked 

 stand from one-fifth to one-fourth of the number of dominant trees. 

 Not only have they larger diameters than the other dominant trees but 

 they are also taller. The wide range of diameters of trees in interme- 

 diate and dominant crown classes which enter into the crown cover 

 is shown in Table 1. Had the density of the more crowded portions of 

 the stand been reduced so that the spacing of all the trees equaled that 

 of those of the favored predominant class there would have been fewer 



11 



