factory means of estimating stocking are by total volume or by 
basal area. Of these two, the basal-area method requires much 
less computation and for practical purposes is as accurate. By 
this method the relation between the actual total basal area per 
acre and the corresponding table values for the particular site 
and age establishes the percentage of normality of the stand. 
No quicker or more satisfactory method of judging normality 
than the basal-area method has as yet been found. Attempting 
to establish normality on the basis of completeness of crown 
cover, total number of trees, number of dominant trees, average 
diameter, or any other easily obtained criterion is for many 
reasons far from satisfactory. 
If the stand is normal to-day, its yield 10 or 20 years in the 
future (but hardly longer) may be predicted from the yield 
tables simply by adding the 10 or 20 years to the present age 
of the stand and reading from the table the yield at that age on 
the site as identified. 
Prediction of yield from an abnormal or understocked stand 
is not quite so reliable. It is possible that a stand not now 
normal tends to become normal as it grows older, but the rate 
of progress toward normality, if any, awaits investigation and 
at present can not be safely predicted. For this reason the 
future yield of a stand known to be understocked at present can 
only be conservatively predicted from the tables by assuming 
that its present percentage of understocking will remain con- 
stant. If a sample plot has but 50 per cent of the basal area of 
a normal plot, all that may be counted upon 10 or 20 years 
hence is 50 per cent of the yield shown in the tables for that 
species and site at the ages then attained. 
For example, if it be assumed that a tract of 50-year-old 
loblolly pine of 750 acres, variously stocked, is to be cut at three 
Si eaae periods in the future, the situation might shape up as 
ollows: 
| 
i Cutting 
Number of acres Site Normal- 
index ity (y a 
Pi, A ae Se Ty Vane See er eS ee SOR eae ae 110 90 60 
AS Uae a her pins tio! ag Mins Fh Sia thaale Selatde e SamOaR ye eerie Sige ay 90 85 7 
DAR | its eae Noh 8 Wa ge ul ae eS ay nn ee a 70 80 80 
_ According to the yield tables, an acre of normal loblolly pine, 
site index 110, will yield at 60 years of age 63,000 board feet, 
international rule. As this particular tract is only 90 per cent 
normal the standard yield must be reduced by 10 per cent, 
which brings it down to 56,700 feet. Similarly the yield for the 
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