Forest Sampling Random Pairs Method

Sampling Trees per Acre Follow a compass line of your choice Starting with where you are standing (point P), look for the nearest tree (Tree A) Only trees with a circumference of 18 in or more should be measured

Sampling Trees per Acre Face Tree A and hold your arms out to your side Find the tree closest to tree A that is behind the line formed by your arms. This is Tree B Do not select a tree in front of your line as Tree B

Sampling Trees per Acre Measure the distance between Tree A and B, record the species of each tree and circumference at breast height (DBH) Return to point P and move 50 feet along the compass line and repeat the process At least 10 pairs should be surveyed

Calculating Trees per Acre After sampling is complete, use the formula below to calculate the number of trees per acre Trees per acre= (AB)/(CD) A=Square feet per acre (43,560 ft2) B= number of pairs of trees randomly selected C= 0.8 (a constant used for forests in our area) D= Total area of the random pairs Found by adding the squared distance of all of the random pairs

Calculating Trees per Acre Sample problem:

Calculating Relative Density and Frequency Calculated for each species identified in forest Relative density= # of that tree/ total # of trees ID’d Example: You identified 5 sugar maples out of a total of twenty trees RD= 5/20 =25% Calculating Relative Frequency Relative Frequency= # of pairs species occurs in/ total # of pairs Example: Sugar maples were ID’d in 5 out of 10 pairs RF=5/10 =50%