VBAR Tables

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VBAR Tables
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VBAR Tables
Point sample calculations need VBARS, not just
volume Any volume table can be converted to a
VBAR table (It doesnt have to be volume, but
its still called a VBAR) VBAR
Volume is from a table or equation Basal area (sq
ft) .005454xDBH2
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Example International ¼ Bd Ft FC 78 volume
VBAR
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VBAR Calculation
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VBARs more similar within height than diameter
Similarity within height depends on amount of
tree not used. Board foot measure doesnt use
most of the tree top.
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If trees were cones Ratio of volume to basal
area for a cone is H/3 regardless of radius
H
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Trees are almost cones, BUT

• We use DBH for basal area instead of stump
  diameter.
• We dont usually use total height or want total
  volume.
• The tree cone is truncated at the top, like a 6
  inch top diameter and basal area is measured 4 ½
  feet up the stem
• So, volume to basal area ratio for a tree is not
  quite H/3
• but its close!

H
DBH
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VBARs by Height
Appendix 3, pages 36 in text
Some change within a height class, but more
difference between heights than between
diameters. As DBH increases, very little change
in VBAR within a height class.
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VBARs by Height
Appendix 5, page 38 in text
As DBH gets bigger the intercept becomes smaller
and less important. VBAR depends on height since
most of the tree is included.
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So What?
An error in height is more important than an
error in DBH. 10 inch, 1 log tree VBAR 66
compared to 12 inch, 1 log VBAR
71 Difference of 5 bd ft 15 inch, 1 log VBAR
75 Difference of 9 bd ft 10 inch, 1½ log
VBAR 88 Difference of 22 bd ft 10 inch, 2 log
VBAR 108 Difference of 42 bd ft Missing a
DBH hardly matters. Missing Height is bad.
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VBARs from volume equations
Cord volume 4 inch top for volume and
height VBAR
As DBH increases, VBAR depends more on height
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Equation without Intercept
Every VBAR within a height class is the
same Dont even have to measure DBH
H is total height