34 
B. YreLp TABLES 
From the data given in the preceding pages the yield tables 
below have been constructed. As has already been remarked, 
pure stands do not occur and, therefore, a percentage com- 
position is given in Figure 5, so that the yield in any mixed 
stand may be ascertained by calculation. It is also true that 
pure ash-oak stands do not occur, but the percentage of 
other trees in the stand will depend greatly on the manage- 
ment. Where the percentage of such trees as red maple and 
gray birch is large at the commencement of the life of the 
stand, the removal of these will form the greater part of the 
early periodic thinnings. 
For the purposes of this yield table, basswood, beech, and 
chestnut may be considered as oak in regard to number per 
acre. Chestnut, however, may now be considered a thing of 
the past owing to the ravages of the disease Endothea para- 
sitica. Both basswood and beech are space demanding like 
oak. Neither of these trees occurs at all freely in the mature 
forest, but it is probable that they were present in the original 
forest in a greater percentage than to-day. Sugar maple, 
black cherry, red maple, black birch, and yellow birch may be 
regarded as ash as regards number per acre. All of these trees 
are crowd enduring and all form clear boles like ash. The 
difference in the height growth of oak and ash at any period 
is small and neither tree is in any danger of being over- 
topped by the other. There is a rather remarkable difference 
in their growth at about the sixteenth year and onwards. 
The annual height increment of ash, which is more regular 
than is the case with oak, suddenly becomes slower, so that 
the general increment at about the seventieth year is only one 
or two inches, while in oak it is about four inches. This sud- 
den decline in the rate of growth also occurs in white pine and 
apparently the height above ground or age at which it takes 
place varies according to the site. 
