32 



Tin; wiiiii; pine. 



to luiilco as good an annual lieight growth as its more- favored neighbors, and can continue the 

 same to the second century. From the table of lici-ihts at various ages it is learned that the 

 success in the Juvenile stages after all tells on the total height growth. 



Tablk IV. — I'triodic hviijht growth, hij decades, of dominant, codominani, and oppressed pine. 



Uffect of rnmjMKition of forest iipoti Iwii/ht (innrlh. 



The height development of \\'hit(' I'ine seems to progress niort^ rapidly when it grows mixed 

 with other species. A striking instance showing how the height growth of White i'ine is bene- 

 fited by the presence of other species is given in the diagram (fig. 2), which represents the height 

 growth of White Pine taken from two sites {a and h) in Presque Isle ('ounty, jVIich. The sites 



were about •"> or <! miles distant from each other. 



/OO 



On site "a " 



titt^-. 



40 60 

 AGE. 



100 



The soil and the moisture conditions on both 

 sites wert^ a])parently identical (fresh sand), as 

 were the total number of trees to the acre (the 

 sample area on site a contained 181 trees and 

 that on site h 18!) trees) and the age of the trees 

 and their distribution over the gruun<l (density 

 of crown cover). The only difference found be- 

 tween the sample areas staked off on both sites 

 was the composition of the forest. Site a con- 

 sisted of a mixed growth of Norway and White 

 Pine, while site h represented practically a pure 

 growth of White Pine save a few small Uemloclc 

 and an occasional Norway Pine. The diagram 

 shows that the \Miite Pine on site n was exceed- 

 ingly stimulated in its height growtli by the 

 preseiK-e of the Norway Pine. 



Tlie associated si)ecies entering into the 

 struggle for light with the White Pine naturally 

 attect the iirogress of the height growth of the 

 pine. The effects of the associated species upon 

 the height growth of White Pine and the period of their influence depend upon the capacity of 

 the associated species to grow in height as well as upon the time when the associated species are 

 either introduced among the pine or received it under their shelter. In (;asc, for instance, hard- 

 woods accomi)any White Pine from the very start the inlluence of the hardwood upon the lieiglit 

 growth of the i)iiic will last only for the first sixty or seventy years, that is, up to the age at which 

 most of the hardwoods practi(^ally reach their maximum height. In case the Norway Pine or the 

 Ilemlock starts simultaneously with the White Pine, the height growth of the White 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 happens to start on ground 

 already covered with other species in siicli a manner as not to be interfere<l with in its growth the 

 associated 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- 

 panying diagram (fig. 3), representing the height growth of White Pine taken from three sites 

 (/, A-, and i) of identically the same coiulitious except as to comi)osition of the forest and thedilfer- 

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

 claj'ey loam underlaid by a laminated shale of indefinite depth. The White Pine on site/ (Clear- 

 field County, Pa.) was mixed with Ilemlock of a large size; the pine on this site had started 



Fig. 'J. — Dia^ftiu showing Ii,-i;;lit ;:iuw11i of White V'ww in PriM^iM' 

 Isk" County, Mich. : Site a, in mixt'd growth: site 6, in jmre growth. 



