You measure trunk size by determining its circumference at a specific height, typically 4.5 feet (48 inches) above the ground, and then often calculate the diameter from that measurement.
Measuring Trunk Size: A Step-by-Step Guide
Measuring the trunk size of a tree, often referred to as Diameter at Breast Height (DBH), is a standard practice in forestry and arboriculture. Here's how it's done:
-
Gather your tools: You will need a measuring tape (preferably a diameter tape or a flexible tape measure) and possibly a helper for larger trees.
-
Identify the breast height: This is typically 4.5 feet (approximately 1.4 meters) above the ground on the uphill side of the tree. Mark this point.
-
Measure the circumference: Wrap the tape measure around the trunk at the breast height mark, ensuring the tape is perpendicular to the trunk's axis. The reference video mentions measuring the circumference at the 48-inch mark.
-
Record the circumference: Note the measurement in inches or centimeters, depending on your preference and the units of your tape measure. For example, the reference video states "The circumference of this tree is 32 inches."
-
Calculate the diameter (optional): While the circumference is a useful measurement in itself, you can calculate the diameter by dividing the circumference by pi (approximately 3.14). The reference video explicitly mentions this calculation: "we're going to divide that by PI. Or 3.14." So, Diameter = Circumference / π. In our example, 32 inches / 3.14 ≈ 10.19 inches.
Considerations for Accurate Measurement
- Sloping ground: On slopes, measure 4.5 feet from the ground on both the uphill and downhill sides of the tree and take the average of the two points as your measurement height.
- Multiple stems: If the tree splits into multiple stems below breast height, measure each stem separately at breast height and record each measurement. If the split occurs at or above breast height, treat it as a single tree.
- Abnormalities: If there's a bulge or deformity at breast height, measure above or below it at the nearest representative diameter and note the location.
- Diameter Tape: Using a diameter tape simplifies the process as it directly displays the diameter when wrapped around the tree, eliminating the need for calculation.
