cruise summaries
DESCRIPTION
Cruise Summaries. Zigzag Transect Method. Used by NRCS foresters Simple and Quick way to determine Average tree diameter Range of tree diameters Trees per acre Stand composition Stand Condition. Main Stand. Zigzag Transect Method. 1. Select Main Stand - PowerPoint PPT PresentationTRANSCRIPT
CRUISE SUMMARIES
Zigzag Transect Method
Used by NRCS foresters Simple and Quick way to determine
Average tree diameter Range of tree diameters Trees per acre Stand composition Stand Condition
Main Stand
Zigzag Transect Method
1. Select Main Stand 2. Choose a Route (X-section of stand) 3. Select a Starter Tree (unmeasured) 4. Choose a Direction 5. Locate Closest Tree of main stand 6. Determine Distance, Species, and
Diameter 7. Rate Tree Condition 8. Repeat until at least 20 sampled
Zigzag Transect Sequence
Zigzag Summaries + Calculations
Average Stand Diameter = sum of DBHs/# of trees
Range of Diameters – smallest tree to largest tree
Average Tree Spacing = total distance/# of trees
Trees per acre = 43560/spacing2
Percent of each species of all sampled trees
Stand condition = percent of each grade of total
Thinning Recommendations
D + x Rule of Thumb X usually equals 6, smaller for western
pines Example
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
COMPARINGFixed plot vs. Variable point
Cruises
Basal Area by tree size
Volume per acre by diameter
Summary of Major Points
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
Expanding Measurements
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
Trees per Acre
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?
Trees per acre
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.
Crop tree release
Accelerated growthprovided byremovingcompetitors
Cost vs. benefit?
DBH
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)
Average logs per tree
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 (more specific than standing tree grading)
Basal Area per Acre
DBH is used to calculate BA, cruise summaries should include this
BA can be used to calculate QMD
Area per area index.
60 ft2 of BA per acre by tree size
Volume per Acre
Takes your measurements to the 3rd dimension
Along with grade and species, used to assign value to stand
Stand Valuation = next topic