36 



\the white pine. 



ARKA ACCRETION. 



VVliile the diametej; accretion decreases in rate contiiiiionsly after the juvenile .stage, the 

 growtli of tlio areas or layer of wood correspoiidinf;? lo tin- diaiiietcr increments follows by no 

 means the sanu; cour.se. 



After the Juvenile stage, which is determined by the formation of a definite crown, and when 

 the diameter has attained at least (! inches the ero.ss section area bcfrins to increase in arithmetical 

 ]irogression; a constantly increasing rate prevails until a maximum is attained, wliicli conies 

 between the sixtieth and one hundred and twentieth year, and then continues remarkably uniform 

 for a long period. No decline is noticeable until after the .second century has begun. In codominant 

 and ojipresscd trees the area as well as th(^ diameter accn^tion mov(! somewhat ditlerentiy, the 

 maximum rate coming later and lasting a shorter time, the decline following soon alter the 

 maximum. 



FORM 1«K\ KI.OI'MKNT, OK TAl'KH. 



Since size of crown and light conditions regulate the amount of diameter growth, it is evident 

 that trees with well developed free crowns form more wood than those crowded, the dominant more 

 than the oppressed, and those on lawns more than those in the deii.se forest. Moreover, in these 

 latter the wood is differently disposed along the trunk than in tlie former. Not only do trees 

 grown in the open throw thc'w energy into braiuih growth, but the accretion on the bole is laid on 

 in layers, increasing in width from top to base. Tiie result is a more rai)i<l tai)cr than in foiest- 

 grown trees, in which each annual layer is wider at the top than at the base of the tree, jirodueing 

 thereby a more cylindrical form. 



The following table exhibits in the measurements of six trees this variation in the width of 

 the same annual rings at ditl'eient heights, and also in general tiie mode of diameter growth in 

 these trees. More elaborate tables, showing the diameter growth of White Pine at various heights 

 iTom the ground for dominant, codominant, and opiiressed trees in various parts of its range, 

 together with diagrams, will be found in the Appendix: 



Diameter growth i}//oreft-groini Irica at nirioiis heights from ground. 



From such tabulations the taper, factor of .shape, or form factor, may 1)0 derived (see Tables 

 II and V in Api)endixj, which denotes the deviation of the shape of the tree from a cylinder. 

 This lactor varies between 0.10 for the older trees and larger diameters to 0.50 for younger and 



