THE RED SPRUCE. 29 



possiDie. Since the mature living timber is the most subject to attack, 

 the cutting over of the remaining virgin tracts, using an approximate 

 diameter limit of 14 inches at breast height, will greatly reduce the 

 danger of subsequent serious damage arising from this source. 



GROWTH. 



Spruce varies more or less widely in growth, form, and development 

 with the character of the stand, the density of the stocking, and the 

 exposure and quality of the soil. Virgin or old-growth stands present 

 a distinctly different set of conditions from the second-growth stands. 



The virgin stands are, without exception, of the natural selection 

 form, in which each tree or small group of trees develops individually; 

 all ages and sizes are represented, from seedlings to overmature 

 veterans, but the older age classes generally predominate. The 

 second-growth stands, on the other hand, are in a large measure of 

 even-aged form, either in groups or over whole areas; the trees all 

 start at approximately the same time and develop as a unit rather 

 than as distinct individuals. The conditions surrounding these two 

 modes of development give rise to differences not only in the rate 

 of growth in volume, height, and diameter, but in the form of bole 

 of the individual tree. 



HEIGHT GROWTH. 



In the virgin forest or in one managed under the selection system, the 

 height growth of spruce bears no definite relation to its age. It is the 

 soil quality, or site quality, whose influence is particularly manifested 

 in height growth. Mature spruce in the virgin-forest types in which 

 it characteristically occurs shows the same relative height develop- 

 ment in Maine and the Adirondacks for the corresponding soil types. 

 The " spruce swamp" shows the least development in height, aver- 

 aging for the tallest trees about 60 feet in Maine and 72 in the 

 Adirondacks, followed by the "spruce flats" and "spruce slopes," on 

 which the heights are nearly the same, namely, 70 feet in Maine and 

 75 feet in the Adirondacks. Spruce reaches its best development on 

 the "spruce and hardwood lands," with heights of 75 feet for Maine 

 and 80 feet for the Adirondacks. The differences in average height 

 for similar types in Maine and the Adirondacks are in large measure 

 accounted for by the fact that the averages for the Adirondacks 

 include a large percentage of virgin growth, while those for Maine are 

 based almost entirely on figures from cull forests, which are lacking 

 in the larger sizes. The inferior height growth in the "spruce swamp" 

 and, "spruce slope" situations is attributed to the fact that not only 

 the growth in these situations is slower, but also that the timber in 

 many cases is second growth. Stands in these situations are par- 

 ticularly likely to be overturned by the wind on attaining a certain 



