Variable Plot Sampling Flashcards
What is variable plot sampling?
A method of sampling based on a trees size rather than its frequency
Who founded variable plot sampling?
Walter Bitterlicke
In variable plot sampling, what is the probability of tallyin a rtree dependent on?
Cross sectional area of tree
Sighting angle used
What did Bitterlicke call variable plot sampling?
Angle count sampling
What is BUF?
Blow up factor - artificially increase basal area to make for easier counting
What is the critical angle?
Angle that defines the blow up factor for a tree.
What is the difference between prism plots and angle plots?
In angle plots, the tree is the center of the plot, eye is the focal point
In prism plots, the prism is the center of the plot. Prism is focal point. Important to hold prism over the center of the plot.
How do you determine a tree’s plot size?
BA x BUF
What is a general rule regarding angle size and BAF?
The smaller the angle, the smaller the BAF, the more trees included in the sample.
Difference between Fixed Area and Variable Plot sampling
Fixed Area - Each Tree has an Equal Chance of getting selected
Variable Plot - Probability of a tree being sampled is proportional to its size. Each tree represents a potentially different number of trees/ha.
BAF
Basal Area Factor - how much BA each tree represents
BAF = 2500 (DBH/Rmax)^2
VBAR
Volume to Basal Area Ratio - Obtained by measuring trees
Tree volume/Tree BA = VBAR
expressed as a number
Stand basal area =
Avg Tree Count/Blowup factor x units for desired area
ex. 10,000 m2/1000 x 10,000m2 per ha = 60m2/ha
Stand volume =
Basal Area x Avg VBAR
PRF
Plot radius factor - determines maximum distance a tree of a given diameter can be from the point to be counted.
PRF = (Rmax(m)/DBH(cm)) or PRF = (0.5/Sqrt BAF)
