Apart from pure monetary values, there are many reasons to why it is a good idea to measure individual trees. You wish to measure your forest to know how well a particular tree is doing in a specific stand. How it competes with other trees and how well it grows in relation to other trees. To determine this, the method most commonly used is to measure the stem diameter. The diameter often correlates with the tree’s biomass or wood volume
Diameter at breast height, or DBH, is a standard measure when talking about trees. The DBH refers to the tree diameter measured at 4.5 feet or 1.3 meters above the ground. DBH is one of the most commonly used dendrometric measurement terms, to estimate the amount of timber volume in a single tree or stand of trees by using the allometric correlation between stem diameter, tree height and timber volume.
The measure for DBH can also be used to estimate tree age in very old tree individuals, since the increment of the diameter is constant and non-reversible feature in the growth.
Bark thickness and texture vary greatly between tree species and can have effects on the diameter measure. The bark can be several centimeters thick, and a measurement of stem diameter over bark can be much greater than of the wood below bark. If you are working with a computer caliper to measure tree diameters, a bark deduction can be set in the software. To check the thickness of bark, a simple bark gauge is recommended. The bark gauge consists of a shaft with a sharp point which is pushed through the bark until the underlying wood is felt. The sleeve around the shaft is then shifted to the surface of the bark and the bark thickness read from the calibrated shaft.
The height for DBH should be equal to the height of an adult’s breast. This measure can differ depending on situation and country. In many cases, the exact height makes little difference to the measured diameter, although it may influence your calculations of the forestry biomass. If the ground is sloping, the reference point may be taken as the highest point on the ground touching the trunk, or as an average between the highest and lowest points of ground. In other cases, the DBH will be at an anomalous place of the trunk, such as a swelling. The girth should then be measured below the swelling, where the diameter is smallest.
There are two dominant methods and tools to measure tree diameters: diameter tapes and diameter calipers. Which method and what instruments you select can depend on different things, such as common standards in your company, area or country, the accuracy demands and what type of vegetation you are working in. For any type of diameter measurement method that you choose to work with, it is important to not squeeze too firmly when getting the measure. For example, no pressure should be used when applying the caliper jaws around the stem.
The diameter tape will be small and easy to carry around with you in the forest. A diameter caliper will be more bulky and heavier to carry. On the other hand, the diameter caliper offers quicker results. As caliper manufacturers, we have put great efforts in lowering the weight and slimming all parts for our calipers, without compromising the product quality. Several Haglöf Sweden caliper models offer for example patented foldable jaws, that make transporting and storing of the caliper easier.
Diameter tapes will measure the average diameter corresponding to the girth of the tree, wheras calipers measure stems across one diameter of their cross-section. When using a caliper to measure the stem diameter, it is common to take two diameter measurements at right angles to each other. The square root of the product of the two diameters is then used as the measure of stem diameter.
With a diameter tape, you will measure the circumference of the trunk and divide this measure by 3 to get the diameter, since the tape is calibrated in divisions of π (Pi) centimeters (3.14159 cm). There are diameter tapes that offer a scale for the conversion from circumference to diameter. The measurement with a diameter tape will presuppose that the tree trunk has a circular cross-section, which is also typically accurate for many plantation trees. Our studies show that diameter tapes generally will over-estimate the diameter, if the tree diameter is irregular. The error when using a diameter caliper will, most often, be smaller compared to a tape and when performing 2x measuring.
Diameter tape versus Caliper
A caliper consists of two parallel arms or jaws. One jaw is fixed and the other can be slided along the graduated measuring scale. The caliper should be held at right-angles to the trunk, with the jaws on either side of the trunk. Precision can be improved on non-circular stems by averaging two caliper measurements taken at right-angles. If using electronic and/or computerized calipers, the diameter measurements are stored and processed, most often along with other information on the tree, the plot, the area and the forest, offering a fuller perspective and enabling further analysis based on factual field data.
Haglöf Sweden offers a big array of different caliper types, models, scale lengths and graduations. Some of the upsides when working with diameter calipers from Haglöf Sweden® are:
- You can select from the largest range of models, graduations and applications to have exactly the caliper you need.
- You will benefit from our continuous product development, based on your and other professional users’ experiences and opinions.
- Remember to ask for custom software and other tailor-made solutions that can be offered thanks to our self-owned and selfrun production facilities.
- You can expect timely and speedy deliveries also for large quantity orders.
- Make sure to accessorize your Haglöf Sweden calipers with unique products designed to improve work efficiency and add value to investments.
- If needed, Haglöf Sweden products can be serviced long after the product warranty is expired.
- Enjoy to work with tested, patented and proven reliable products that are fully adapted for tough and demanding professional use.
Haglöf Sweden products are manufactured according to our strict Quality Management System. We understand the true essence of quality for the professional user.