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   The following table shows the relationship of age and average di-
 ameter of all plantations studied, and is a fair indication of what we
 may expect from most planted stands, if they are reasonably well
 stocked.
                                 TABLE V
     Table of Average Diameter and Age for White, Norway, and Scotch Pine
                  and Norway Spruce Plantations in Wiscessin
               White Pine     Norway Pine     Scotch Pine    Norway Spruce
               Average        Average         Average         Average
 Plantation    Diameter        Diameter        Diameter        Diameter
    Age       Breast High     Breast High     Breast High     Breast High
               (4% feet)      (4% feet)        (4% feet)       (4% Ifeet)
   Years        Inches          Inches          Inches          Inches
      5             0              0               0                0
      10           1.2            1.2              1.2             1.0
      16            8.8            8.4            8.2             2.0
      20           5.-1            5.8             5.2             8.4
      25           6.4            6.9             7.2             4.7
      80           7.4            8.4                             6.0
      5           8.2             9.7                             7.0
      40           8.                                              8.0
      45           9.5
      55          10.8
      60          10.7
  Note: Add two or three years for total age from seed for the pines and
three or
four years for spruce.
  Based on diameter measurements of 2.455 Norway pine in 11 plantations,
2.185
Scotch pine In 12 plantations, 2.861 white pine in nine plantations and five
wind-
breaks, and diameter measurements of 559 Norway spruce and a complete stem
analy-
sis of 69 Norway spruce. With the exception of two white pine plantations,
all were
growing on sandy soils, mostly Plainfield sand. At the age of 25 years, all
pine
plantations averaged six Inches or more in diameter. At 8o years ine plantations
in any section of the state should safely average over seven inches. Scotch
pine av-
erage about one and one-half inches greater in diameter than Norway, and
one inch
greater than white pine at 80 years of age.
  The last readings on Norway and Scotch pine were obtained by projecting
the
curve, as no plantations of over to years of age were obtainable for these
two species.
  The average spacing for white pine was 8 x 8 feet, or 64 square feet per
tree, for
Norway pine 6 x 6 feet. or 86 sque- feet, andy for Scotch pine 5 x 6 feet,
'or s0
square feet per tree. The exact spacing of the plantation of Norway spruce
is not
known but It was quite close, possibly 4 x 4 feet. mixed with Scotch pined
which has
died ot.
Volume Production and Yield per Acre
  The amount of merchantable material that a stand produces in a
given time is the chief basis for determining the value of a forest
plantation. Therefore, knowledge of what a few Wisconsin plantations
have produced is helpful in indicating future volume growth. This
volume is generally expressed either in cubic feet, cords, or board
feet. The most accurate method.of showing what a stand contains is
to determine its contents in cubic feet. Board foot measure is used for
large dimension stuff and saw logs, but does not show accurately the
true amount of material actually found in a log, especially in small-
sizes. However, a stand may contain a considerable volume in cubic
feet and yet not be merchantable because it has not yet reached suffi-
cient size to be taken as a merchantable product. It is iniportantthere-
fore to know what sizes, and especially the minimum       sizes, that ma-
terial for various uses are marketable.
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