CONDITIONS OF DEVELOPMENT. 



43 



LIGHT UEljUIREMENTS. 



The capacity of the White Pine to keep its i)lace in mixture with tlie liardwoods is probably 

 mainly due to its shade endurance. In this respect it excels all pines with which we are acriuainted. 

 Pines are, as a rule, rather light-needing species, and are usually at a disadvantage in the mixed 

 forest, unless compensating inriuences 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- 

 sequence of its shade endurance, it does not clean itself of its branches as readily as other pines; 

 not only do the lower branches remain green for a long period in spite of the shade of the superior 

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



As this shade endurance is, however, only relative, and as many of the associates possess it 

 in greater degree, the additional advantage of rapid height growth alone saves the pine 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 Pine is scanty. 



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

 shadier comi>auions, for, as a rule, the best quality, cleaner boles, and absence of black knots, 

 which denotes earlier cleaning, are found iii such association. Yet, in these mixtures the trees are 

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

 height growth ceases sooner, lu 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 are less clean and less free of knots. 



Its shade endurance is decidedly less than that of the Spruce, 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, beiBg less on the 

 drier than on the fresher soils. 



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

 cial!}^ where the hardwoods have been thinned out to some extent, or wliere, 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 first, 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 freriueutly does the reproduction take place in groups, 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 gregariousuess 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 repi'oduction, as is apparent from the following table of acre yields of young growth taken 

 at various places in Xew England : 



Taulk VII. — Acre yield of ijOHUij pine groves. 



