Tree girth measurement

It is one of the most ancient, quickest, and simplest of foresters' measures of size and records of growth of living and standing trees.

[1][2] On a slope this is considered as halfway between the ground level at the upper and lower sides of the tree.

Other commonly used parameters, outlined in Tree measurement include height, crown spread, and volume.

In these older accounts the girths were often taken at ground level and incorporated considerable basal flare at the base of the tree.

[1][2][12] Separating data from single trunk and multi-trunk trees is critical to maintain a valid database of measurements.

In spite of the apparent simplicity of wrapping a tape around a tree trunk at breast height, errors in this measurement are common.

The Native Tree Society measurement guidelines[1][2] also generally follow the American Forests prescription, with some additional elaborations.

[citation needed] If the tree is leaning, measure the circumference at 4+1⁄2 feet (1.37 m) along the axis of the trunk.

Measuring on the upslope side if often easier, it is also higher on the tree and likely will include less of the flare at the base of the trunk, and when measuring extremely large trunk on a slope the upslope side of the girth loop will always be above ground level.

Consider, the tree started as a single sprout and grew upward and outward from that point.

In addition this is a reference point that is present and consistent in all trees no matter the height of the girth measurement.

Even if the girth is measured at a non-standard height because of low branching, a large burl, or even on the upslope side of a large girth tree on sloping ground, all heights can still be consistently referenced to this single point present on all trees.

[citation needed] Measuring tree girth directly is a common educational technique allowing students to learn about their local environment in a practical manner.

A monocular w/reticle is a telescope with a built in scale that can be used to accurately measure the width of objects such as the diameters of trees from a distance.

The farther away the object is from the surveyor, the smaller it will appear in the telescope and the width will read as fewer units on the scale.

The distance from the measured section of trunk multiplied by the reticle reading and divided by an optical factor results in the diameter of the target.

For best results the scaling factor should be tested and calculated for each individual device rather than just using the manufacturer's default value.

Photographs of trees can be used to determine girth or other measurements if there is a something of known size in the photo to provide a scale.

The method may be used to calculate the girth of trees in historical photographs where the true dimensions are unknown.

Assumptions would need to be made about the distances involved and the size of the people in the photograph, but reasonable estimates are possible.

[16] Preliminary tests are being conducted by the NTS to apply the photographic process to volume modeling of trees.

[17][18] A key consideration for many people is that only a minimal amount of equipment is needed to make these calculations: A laser rangefinder, a reference object (ruler), a digital camera, and Excel.

This process will be less accurate than measurements taken with a telescopic reticle, but will be able to generate meaningful close approximations of tree volume.

This occurs frequently in some species when the initial trunk has been damaged or broken and in its place two or more new shoots grow from the original root mass.

These trees should be documented even if the results are in the form of a written narrative rather than a collection of numerical measurements.

Banyan-like trees similarly consist of multiple trunks spread across a large area.

The Tule tree has a diameter of 38 feet 1.4 inches (1,161.8 cm) as measured by tape wrap, but because of its irregularity a cross-sectional wood area expressed as a circle gave an effective diameter of only 30 feet 9 inches (937 cm).

A series of measurements from the reference lines to the edge of the trunk mapping the irregularities of the tree surface and converted to Cartesian x-y coordinates.

Taylor[22][23] has been developing a cloud mapping process using optical parallax scanning technology whereby thousands of measurements are made around the trunk of a tree.

By contrast, the (roughly) 300-year-old Ice Glen pine in Stockbridge, Massachusetts shows approximately half the annual growth rate of trees in the 90- to 180-year age range, averaging just 5.8 cubic feet (0.16 m3) per year over a five-year monitoring period.