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Criteria for Ranking Iowa's Big Trees Trees are ranked based on three measurements: circumference, height and crown spread. Ranking is determined by total points. Circumference: Measure around the tree trunk at 4.5 feet above the ground. If the tree forks at that point, the measurement is made below this where the circumference is least. Circumference counts one point for each inch. Height: This measurement can be difficult to make, but is important. An estimate of height can be made using a yardstick. First, measure 100 feet from the tree. Next, hold the yardstick vertically, 25" from the eye. Align the zero inch mark on the yardstick at the base of the tree and note the inch mark that aligns with the top of the tree. Every inch equals 4 feet of height. Height contributes 1 point for each foot. Crown spread: Measure from a point directly below branch tips on one side of the tree to a point directly below branch tips on the other side of the tree. Make a second measurement at right angles to the first. Average the two measurements. Crown spread counts for 1/4 point for each foot. |
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