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Used by NRCS foresters
Simple and Quick way to determine
Average tree diameter
 Range of tree diameters
 Trees per acre
 Stand composition
 Stand Condition
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Select Main Stand
Choose a Route (X-section of stand)
Select a Starter Tree (unmeasured)
Choose a Direction
Locate Closest Tree of main stand
Determine Distance, Species, and Diameter
Rate Tree Condition
Repeat until at least 20 sampled
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Average Stand Diameter = sum of DBHs/# of trees
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Range of Diameters – smallest tree to largest tree
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Average Tree Spacing = total distance/# of trees
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Trees per acre = 43560/spacing2
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Percent of each species of all sampled trees
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Stand condition = percent of each grade of total
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D + x Rule of Thumb
X usually equals 6, smaller for western pines
Example
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If you determined that the average tree spacing was
12 feet, then trees per acre was estimated as
43560/122 = 303
If average tree diameter was 9 inches, 9 + 6 = 15
Ideal trees per acre = 43560/152 = 194
Thus 303 – 194 = 109 trees per acre need to be
removed to provide adequate spacing
Fixed plot vs. Variable point Cruises
Fixed Plot
Variable Point
Sampling based on
Frequency of occurrence
Tree size
Expansion Factor
Same for all trees
Varies by tree
Best for
Total stems and number
of small trees
Number of large trees
Best for
Long term and repeated
measuring
Temporary plots
Best for
Distribution of DBHs
Basal area and volume
estimation
Tally determined
Distance from plot
center
Angle device over point
Misc
Slope correction harder
than angling prism
Missing large distant
trees, Missing hidden
trees in dense stands
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Number of tallied stems for the tract by species
Average DBH, DBH range, QMD
Merchantable Height (average number of logs)
Basal Area Estimates
Board Foot Volume Estimates
Cull Deductions
Tree Grades
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Number of trees measured can be expanded to
express number of stems per acre for each
species. There is no index of tree size.
Generally more stems = smaller stems. Are
they too crowded to grow well?
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A young natural stand of hardwood trees starts
with 4000 to 6000 stems per acre. At maturity,
when they measure about 20 inches in
diameter, less than 100 trees per acre will
survive. This is a natural selection process and
it is slow, requiring 150 to 200 years or more to
complete.
Mechanical thinning allows ‘crop’ trees room
to grow at a faster rate, obtaining mature size
in fewer years.
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Accelerated growth
provided by
removing
competitors
Cost vs. benefit?
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Could summarize and report average DBH of
stems. If population isn’t normally distributed,
this could lead to false conclusions. Adding an
indicator of variance sheds more light.
Could use other measures of central tendency
like median or mode.
Merchantability depends on that local mills are
buying. (species, size, grade)
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Merchantable height indicator of stand age and
quality
When dominant trees harvested, most will
have similar heights (total and merchantable)
Bucked into manageable sizes for hauling (16’
or less)
Each log graded for lumber yield estimate
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(more specific than standing tree grading)
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DBH is used to calculate BA, cruise summaries
should include this
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BA can be used to calculate QMD
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Area per area index.
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Takes your measurements to the 3rd dimension
Along with grade and species, used to assign
value to stand
Stand Valuation = next topic