Chance and Hannah work together to measure a tree in the T.A. Forest.
The Biltmore stick has multiple uses in the woods and is an important tool for any forester cruising a woodlot in an effort to estimate stand value. The stick is calibrated to help students first estimate diameter at breast height, or DBH. This is the diameter of the tree at 4.5 feet above the ground. To do this, the stick must be held 25 inches from the eye and lined up so that the left end of the stick lines up with the left edge of the trunk. Then, without moving their head, students peer over and observe where the right side of the trunk intersects with the stick. The Biltmore stick is calibrated based upon laws of trigonometry to give a very accurate estimate of diameter when used correctly.
Proper alignment of a Biltmore stick on a tree with a DBH of 14".
Ares flashing perfect form while measuring DBH.
Once the DBH has been determined, students step back 66 feet, or 1 "chain", from the tree and hold the stick vertically with the base of the stick lined up at what would be the stump height. The stick is again marked at intervals based upon trigonometry to show how many 16 foot sawlogs are present in a given tree. Here, students must be able to judge where a tree goes from a merchantable log to firewood.
A red maple with one merchantable sawlog. Everything above the number one could be used for firewood.
Seth works to determine the number of sawlogs in a tree after stepping back 66 feet.
Finally, the Biltmore stick has a table printed on it that indicates the rough volume of wood present in a tree based upon its DBH and the number of sawlogs. These numbers are given in board feet, the common unit of volume for lumber. One board foot is 12"x12"x1".
A look the markings on a Biltmore Stick.
Students in Trees and the Maine Forest recently worked to complete an assignment in which they determine the value of ten trees flagged in the TA forest. They must first determine the DBH and number of logs in each tree, then utilize the table on the Biltmore stick to calculate how many board feet of lumber are in that tree. Once the volume of lumber from each tree is determined, they utilize the most recent timber values available for our area to estimate monetary value of each tree. When all ten tree values are combined, students are often impressed with the value of our forest resources on campus. This leads to great conversations on woodlot management to maximize commercial value as well as wildlife habitat. When done correctly, both wildlife and property owners can benefit from thoughtful harvest. Learning to use the Biltmore stick is not only a cool skill for my students, it also helps to change their frame of reference when walking through the forest or even their neighborhood. I love hearing stories about high value trees that students have observed around town, there is no better sign that concepts from class are truly sticking.
Special thanks to Allie Gross for her photography in this post.
