IMPROVING THE CROP. 298 



confines the lateral growing space, and hence prevents the development of side branches and 

 forces the growth energy of the soil to expend itself in height growth 5 the crown is carried up, 

 and long, cylindrical shafts, clear of branches, are developed. A close stand thus secures desir- 

 able form and quality. Yet, since the quality of wood production or accretion (other things being 

 equal) is in direct proportion to the amount of foliage and the available light, and since an open 

 position promotes the development of a larger crown and of more foliage, an open stand tends to 

 secure a larger amount of wood accretion on each tree. On the other hand, a tree grown in the 

 open, besides producing more branches, deposits a larger proportion of wood at the base, so that 

 the shape of the bole becomes more conical, a form which in sawing proves unprofitable; whereas 

 a tree grown in the dense forest both lengthens its shaft at the expense of branch growth and 

 makes a more even deposit of wood over the whole trunk, thus attaining a more cylindrical form. 

 While, then, the total amount of wood production per acre may be as large m a close stand of 

 trees as in an opeu one (within limits), the distribution of this amount among a larger or smaller 

 number of individual trees produces different results in the quality of the crop. And since the 

 size of a tree or log is important in determining its usefulness and value, the sooner the individual 

 trees reach useful size, without suffering in other points of quality, the more profitable the whole 

 crop. 



NUMBER OF TREES PER ACRE. 



The care of the forester, then, should be to maintain the smallest number of individuals on 

 the ground which will secure the greatest amount of wood growth in the most desirable form of 

 which the soil and climate are capable, without deteriorating the soil conditions. He tries to 

 secure the most advantageous individual development of single trees without suffering the disad- 

 vantages resulting from too open stand. The solution of this problem requires the greatest skill 

 and judgment, and rules can hardly be formulated with precision, since for every species or combi- 

 nation of species and conditions these rules must be modified. 



In a well-established young crop the number of seedlings per acre varies greatly, from 3,000 

 to 100,000, according to soil, species, and the manner in which it originated, whether planted, sown, 

 or seeded naturally. 1 Left to themselves, the seedlings, as they develop, begin to crowd each 

 other. At first this crowding results only in increasing the height growth and in preventing the 

 spread and full development of side branches 5 by and by the lower brandies failing to receive 

 sufficient light finally die and break oft— the shaft u clears itself." Then a distinct development of 

 definite crowns takes place, and after some years a difference of height growth in different indi- 

 viduals becomes marked. Not a few trees fail to reach the general upper crown surface, and 

 being more or less overtopped, we can readily classify them according to height and development 

 of crown, the superior or "dominating" ones growing more and more vigorously, the inferior or 

 " dominated" trees falling more and more behind, and finally dying for lack of light, and thus a 

 natural reduction, in numbers, or thinning, takes place. This natural thinning goes on with vary- 

 ing rates at different ages, continuing through the entire life of the crop; so that, while only 4,000 

 trees per acre may be requii ed in the tenth year to make a dense crown cover or normally close 

 stand, untouched by man, in the fortieth year 1,200 would suffice to make the same dense cover, 

 in the eightietb year 330 would be a full stand, and in the one hundredth not more than U50, accord- 

 ing to soil and species, more or less. As we can discern three stages in the development of a 

 single tree — the juvenile, adolescent, and mature — so, in the development of a forest growth, we 

 may distinguish three coiresponding stages, namely, the u thicket" or brushwood, the u pole-wood ?? 

 or sapling, and the "timber" stage. During the thicket stage, in which the trees have a bushy 

 appearance, allowing hardly any distinction of stem and crown, the height growth is most rapid. 

 This period may last, according to conditions and species, from five or ten to thirty and even forty 

 years — longer on poor soils and with shade enduring species, shorter with light-needing species on 

 good soils — and, while it lasts, it is in the interest of the wood grower to maintain the close stand, 

 which produces the long shaft, clear of branches, on which at a later period the wood that makes 

 valuable clear timber may accumulate. Form development is now most important. The lower 

 branches are to die and break off before they become too large, With light-needing species and 



l If the crop does not, at 3 to 5 years of age, shade the ground well, with a complete crown coyer or canopy, it 

 can not he said to be well established and should he filled out by planting. 



