THE NORTHERN HARDWOOD FOREST. 



21 



within its geographical range. Substantially pure, even-aged yellow 

 birch stands are especially abundant in the eastern mountains from 

 Maine to Pennsylvania. (PI. X, fig. 1.) Pure, even-aged stands of 

 sugar maple or of beech are uncommon (PI. X, fig. 2), and basswood 

 and elm hardly ever predominate in the second-growth except in 

 small groups among other species. 



The following measurements of second-growth hardwood stands 

 made in the course of the study illustrate the growth and composition 

 of young forests of various ages and species. The measurements were 

 made in small sample plots, the sizes of which are given; and the vol- 

 umes and ages were determined by means of sample trees represent- 

 ing arbitrarily fixed diameter groups. 1 The volumes are on an acre 

 basis. As a matter of fact, the composition represented by a sample 

 plot was in most cases less than an acre in extent, the plot repre- 

 senting that portion of the second-growth stand in which the desired 

 species was most abundant. The stands were selected at random 

 and show about the average growth, in cubic feet and cords, for the 

 mountain lands. 2 The volume measurements were of merchantable 

 fuel wood material in trees 3 inches and over in breast-high diameter 

 to a minimum diameter limit of about 2 inches. The cubic-foot vol- 

 umes were reduced to cords by dividing by 85. The crown density 

 is shown in tenths, perfect density being 1. The crown density of 

 birch stands, however, is rarely greater than 0.9, which may be con- 

 sidered perfect. 



BIRCH PLOTS. 



New Hampshire. 

 Plot No. 1.— Age, 43 years; yield, 24.2 cords per acre; height of dominant trees, 55 to 60 feet. 



Species. 



Propor- 

 tion 

 based on 

 volume. 



Number 

 of trees 

 per acre. 



Diameter breast- 

 high. 



Volume 

 per acre. 



Average 

 annual 



Average. 



Ex- 

 tremes. 



growth 

 per acre. 





Per cent. 

 88.0 

 8.0 

 2.2 



1.8 



496 

 40 

 24 

 16 



Inches. 

 5.8 

 6.1 

 4.2 

 4.5 



Inches. 



2 to 10 



3 to 10 



2 to 5 



3 to 5 



Cubicfeet. 



1,806 



166 



46 



38 



Cubicfeet. 

 45.15 





4.15 





1.15 





.95 







Total 



100.0 



576 







2,056 



51.40 











Benton township, Grafton County, N. H., near GlenclifT; western slope of Mount Moosilauke; altitude 

 1,500 feet; slope 25 per cent west by north; soil rather shallow, loamy sand with 3 inches of humus; plot 

 one-eighth acre, representing one-fourth acre stand surrounded by uneven-aged growth; density 0.8; 

 reproduction, sugar and red maple, abundant. 



i This method is described in H. S. Graves's "Forest mensuration," pp. 229-231, 1906. 

 2 The yield of mixed second-growth hardwood stands in Vermont is given in Vermont Agricultural 

 Experiment Station Bulletin 176, "The management of second-growth hardwoods in Vermont." 



