32 



TIIK Wlllli; I'lXE. 



to iiiiike as j;(Mi(l Mil iiiiiiUiil liciylit giowtli as its inoro-favored neighbors, and can continue tlie 

 Hivnio to till) second century. From tlie tabic oC licifihts at various ages it is learned that the 

 success in the Juvenilo stages aftei' all tolls on tlie total heiylit };n)\vth. 



'I'ahi.K IV. — I'rriudio hrii/hl tjrowlhy hy UecadcHf of ilinitiintnt, rtKlomiimnI, and (ipjirrnni'd pine. 



KlTect of vompoxition of forent ii/ion hcifiht growth. 



The lifi;;lit dcvelopiiiciit oC \\'liite Pine seems to progress more rajiidly wlieii it grows mixed 

 witli other species. A striking instance showing how the height growth of White Pine is bciie- 

 fite<l l)y the jiresenee of other si)ecies is given in the diagram (fig. 2), which r(!]>rescnts the lieight 

 growth of White Pine taken from two sites (d and />) in J'resijue Isle (!ouiity, Mich. The sites 



were about •"> or (i miles distant from each other. 

 lOOr" i . .1 , ., .1.. :: 1, ;ii"illllllliiiULiu.l The soil and the moisture conditions on both 



sites were api)arently identical (Iresli sand), as 

 were the total number of trees to tlie acre (the 

 sample area on site a contained LSI trees and 

 that on site h IS!) trees) and the age of the trec^s 

 and their distribution over the ground (density 

 of crown cover). The only difference found be- 

 tween the sample areas staked off on lioth sites 

 was the comiiosition of the forest. Site a con- 

 .sisted of a mixed growth of Norway and White • 

 Pine, while site h represented practically a jmre 

 growth of White Pine save a few small Ilciiilock 

 and an occasional Norway Pine. The diagram 

 shows that the White Pine on site a was exceed- 

 ingly stimulated in its lieight growth by the 

 ^rj presence of the Norway Pino. 



The associated species entering into the 

 struggle for light with the White Pino naturally 

 afloct the progress of the height growth of the 

 pine. The eflects of the associated species upon 

 the height growth of White Pine and the i>eriod of tlieir influence depend upon the capacity of 

 till" associated species to glow in lieight as well as ujioii tlu< time when the associated 8]iecies are 

 either introduced among the pine or i-eceived it under their shelter. In case, for instance, hard- 

 woods aeeompany White Tine from the very start the iutlueuce of the hardwood upon the height 

 growth of the pine will last only for tlni first sixty or seventy years, that is, u]) to tlm ago at which 

 most ol' the hardwoods practically reach their maximum height. In case the Norway Pine or the 

 Hemlock starts simultaneously with the White Pine, the height growth of the ^Vhite Pine will be 

 stimulated to a considerably later age, because the Hemlock or Norway Pine continues to grow in 

 height at a similar rate for a longer time. When the White Pine hapiiens to start on ground 

 already coven^l with other speities in such a manner as not to be interfered with in its growth the 

 a.ssociated species, if capable of growing in height to a later age, will stimulate the height growth 

 of the White Pine for a considerably longer period. All this is clearly demonstrated in the accom- 

 Itanying diagram (fig. .'!), representing the height growth of White Pine taken from three sites 

 (_/', /.', and /) of identically the same conditions except as to composition of the forest and thtuliHer- 

 eiice in the ages between the pine and associated species. All three sites had a well drained 

 clayey loam underlaid by a laminated shah; of indefinite dciitli. TheWhite Pine on sitey"(01oar- 

 lield County, Pa.j was mixed with lleuilock of a large size; the pine ou this site had started 



40 60 

 RGB. 



Kni. 'J. -l>iagrimi Bhowiu;; }ifii;hl ;;iowlli *)f Wliilt- I'iiiu in PnH<iin 

 IhUi County, AficU.: Site a, iu mixed yirowtli; site 6, in imre growth 



