CONDITIONS OF DEVELOPMENT. 



43 



I.IlillT KEqUIKEMENTS. 



The capiicity of the White Pine to keei) its phxco in mixture with the hardwood.s is probably 

 niaiuly due to its shade cntbirauce. In tliis respect it excels all pines with which we are a(!riuainted. 

 IMnes are, as a rule, rather light-needing s])ec,ies, and are usually at a disadvantage in the mixed 

 forest, unless compensating mlluences are in their favor. The White Pine is an exception. As a 

 consequence, it is capable of forming dense thickets, supporting a larger number of trees per acre 

 and producing a larger amount of material than the more light-needing species. Also, as a con- 

 se(|uence of its shade endurance, it does not (dean itself of its branches as readily as otherpines; 

 not oiil^-do the lower branches remain green for a long period in spite of tlie shade of the superior 

 tiers of foliage, but they persist after they are dead for many years. 



As this .sliatb; cndnrance is, however, only relative, and as many of the associates possess it 

 iu greater degree, the additional advantage of rapid hoiglit growth alone saves the iiine from 

 being after all suppressed by its shadier companions. Yet, these succeed in keeping the young 

 progeny of the pine subdued, and hence the observation that in the dense virgin forest of hard- 

 woods the reproduction of White I'iiie is scanty. 



The ditticulty of cleaning itself of dead branches seems to be overcome by association with 

 shadier companions, for, as a rule, the best quality, (deaner boles, and absence of black knots, 

 which denotes earlier cleaning, are found in such as.sociation. Yet, in these mixtures the trees are 

 apt to be shorter bodied, since tlie hardwood compaiuons are shorter bodied and the stimulus to 

 height growth ceases .sooner. In the pinery proper the; stimulus to height growth exerted by the 

 neighbors continues longer; hence, longer shafts are found here, other conditions being the same, 

 although the boles ;ire less clean and less free of knots. 



Its shade endurance is decidedly less than that of the Si)ruce, which maintains itself, but 

 not thriving under the dense shade of Maple, Birch, and Beech, where White Pine seedlings and 

 saplings are not to be found, although they sustain perfectly the shade of oaks. To be sure, this 

 shade endurance is to some extent dependent on moisture conditions of soil, being less on the 

 drier than on the fresher soils. 



This relatively high .shade endurance permits ready natural reproduction of the pine, espe- 

 cially where the hardwoods have been thinned out to some extent, or where, after clearing, all 

 species start their race for reoccupation of the soil with equal chance. The pine then appears in 

 the young hardwood growth in single individuals at tirst, somewhat behind in height, but finally, 

 when it enters upon the period of rapid height growth, it outgrows its competitors and is assured 

 of its place. 



More frequently does the reproduction take place in grouiJS, smaller or larger, the many areas 

 of "second growth" of several acres in extent, which are found throughout the hardwood coppice 

 of Massachusetts, showing that tendency toward gregariousness so characteristic of the conifers. 

 A further discussion of the conditions of reproduction and the yield occurs in the portion devoted 

 to the discussion of forest management and of forest yield. 



In these natural reproductions the trees grow close together, that is, close for unaided nat- 

 ural reproduction, as is apparent from the following table of acre yields of young growth taken 

 at various places in New Knglaud: 



Tahlk VII. — Acre yield of ijoiing inne groves. 



