New Mexico Envirothon Forestry Equipment & Measurements Study Guide Diameter/logger’s tape – A tape measure specially graduated so that diameter may be read directly when the tape is placed around a tree stem or log. Some may also measure length or distance. Clinometer – An instrument used for measuring the angle of an incline. It measures the vertical rise or fall from horizontal at a specified distance from the observer. They are used in forestry to measure grade angles (slope steepness) and tree height. GPS unit – This equipment works with satellites to give accurate map information. Laser Rangefinder - Used for distance and heights (total tree height, crown base height, defect height, etc.). Prism (wedge) – A point Basal Area Gauge - sampling instrument that is a same use as a prism and tapered wedge of glass. It is contains several BAFs in calibrated for different Basal one instrument. Area Factors (BAF). Hand compass – An instrument which indicates magnetic north. The essential parts of a compass are the magnet, usually in the form of a needle, which is balanced on a jeweled bearing or pivot, and a graduated circle with 360 degrees of azimuth or four 90 degree quadrants. The components are housed in a box or frame that has a sighting device with which to aim at the objective. It is used for orienting maps and determining direction. Increment borer – A tool used to take a small core from the bole of a tree to determine growth rate and age. Relaskop – An instrument that can be used to measure stand basal area and tree height and diameter at any point up a tree bole. The relaskop works as a rangefinder, a clinometer, a dendrometer, an angle gauge, and a slope correction device. Flagging – PVC vinyl or other material that is about an inch wide on rolls available in multiple colors and used in surveying, forestry, orienteering and landscaping. Tree marking gun – A paint applicator used with tree marking paint to mark trees on a plot of land indicate whether to cut or to leave on a thinning site. Chainsaw – A piece of equipment that is used to cut down trees, trim trees or cut downed trees into logs or firewood. Densiometer – This instrument estimates forest canopy coverage. It can measure forest overstory density from unobstructed sighting positions. The instrument uses a spherical­ shaped reflector mirror engraved with a cross­ shaped grid of 24 quarter inch squares. It is helpful when establishing spacing standards in forest thinning and determining light requirements for regeneration. Hand lens/field microscope – A small magnifying glass that can be carried in a pocket and used in the field to magnify an object. Tree caliper – An instrument used for determining tree and log diameters by measuring their rectangular projection on a straight graduated rule via two arms at right angles to the rule itself. One of them slides along the rule. Hip chain – This is a measuring tool that attaches to a belt. A thread is attached to an object and as the person walks the thread is drawn from a spool attached to a counter inside a case, and the distance traveled is displayed on the odometer­type counter Forestry – Measurements (From Maryland Envirothon website http://www.dnr.state.md.us/education/envirothon/forestry/measurements.html ) Pacing: The most basic forest measurement is pacing or counting your number of steps to determine how far you’ve traveled in the woods. A compass will help you determine which direction you are walking, but pacing allows you to estimate distance. In forestry, distance measurements are based on a chain, which equals 66 feet. Many years ago surveyors literally dragged a 66­foot­long chain around with them to measure properties, which were measured in chains and links. Today, foresters measure chains by knowing how many steps they take in 66 feet. To determine your pace, measure out 66 feet using a 100­foot measuring tape, and count every other step (for example, every time your right foot hits the ground). Most people have between 12 and 15 paces per chain. CHAIN FACTS: • 80 chains = 1 mile (1.61km) • 10 square chains = 1 acre (very helpful in determining the size of wildfires!) • Several forestry tools are calibrated to be accurate at one chain. Tree Diameter: Tree diameter is an important measure of tree growth, especially when combined with additional measurements such as the height and age of a tree (such as determining the volume or site index of a tree). Diameter is always measured on the uphill side of a tree at 4.5 feet up the trunk (Diameter at Breast Height, DBH) using a diameter tape (d­tape). The first thing you’ll notice about the d­tape is that the inches look a lot longer than usual (3.14 inches to be exact). This is because the d­tape is calibrated in “diameter equivalents of circumference by inches and tenths of inches” saving you the trouble of converting circumference into diameter. Remember that diameter measurements should be expressed to the nearest tenth of an inch (for example 11.7”). The reverse side of the tape shows feet calibrated in feet and tenths of feet. Measure DBH @ 4.5' from forest floor (the pictured individual is about 5' tall) Tree Height: Angle up - Angle down * (distance/scale) Tree height is measured using the principle of triangulation with a clinometer. Of all the forestry tools you will use, the clinometer requires the most practice and skill. Assuming that the tree grows at a right angle to the ground (even on a slope), we use the clinometer at a known distance from the tree using the following steps: • With both eyes open, aim the black crosshair of the clinometer level with the base of the tree at the soil. Using the (normally) left-hand scale you will read a “negative” number if the tree is on level ground or down slope. You will read a “positive” number if the tree is up slope. • With both eyes open, aim the black crosshair of the clinometer to the top of the tree. This is a tricky measurement because your view may be obscured by leaves or nearby tree branches. If the top of the tree were an open umbrella, you’d want to be aiming at the point on the top of the umbrella. Note: the left scale is often percent (1/100) and right either topos (1/66), or degrees (1/90). • Add or subtract the numbers: 1) If both top and bottom values are of the same sign (+ or -), the two numbers are added together.If the values are of different signs (one + and one -), the base reading must be subtracted from the top reading. Ex 1: Up = +50% Down = -20% 50 - (-20) = 50+20 = 70 Distance = 50' 50/100 = 0.5 70 * 0.5 = 35' Tall 2) Divide distance by 100 and multiply the sum from step 1 by this value. Note: if using a different scale, divide distance by that scale e.g. D/66 or D/90. Ex 2: Up = +46% Down = +13% 46 - 13 = 33 Distance = 100' 100/100 = 1 33 * 1 = 33' Tall Determining the volume of a tree: Once we know the diameter, height, and the number of logs a tree contains, we can determine the volume of the tree. This is an important number, especially when determining the value of the tree if it is sold for forest products. Just like in geometry, we are essentially determining the volume of a cylinder (tree trunk). In forestry, volume is expressed in board feet, which is an imaginary chunk of wood 12” X 12” X 1” thick. To make measurements easier, foresters often use volume tables to quickly compute volume. Many forests use the International ¼ inch rule volume table. Determining tree age: Another important measurement is tree age. Not only is counting the number of growth rings important to determine the tree’s age, but interpreting the spacing of growth rings can tell us much about its life. Examining the growth of a tree can tell us many things about the growing conditions about the site, or environment the tree is growing in. Because trees are many times older than we are, growth rings serve as a “history book” of the tree and its surrounding community. Droughts, wet seasons, injuries, and even forest fires can be reflected in tree growth rings. On standing trees, age is determined by using an increment borer, which is a threaded hollow drill that is turned by hand into a tree’s trunk until the borer reaches the center of the tree. The increment core, a pencil-thin sample of wood, is extracted from the trunk, showing the tree’s growth rings and ring spacing. Although this boring does not usually harm forest trees, it is not recommended for urban or other “specimen” trees. Annual growth includes early wood (light colored, less dense ring from active growing season) and late wood (dark, dense ring from late season/fall dormancy). Only count one or the other (early or late wood) to determine age. Starting from the outside (near bark), count late wood to the pith (inner-most ring). Note the boring in this picture is near ground level. This method provides an estimate closer to "true" age. (There should be more rings at ground level than breast height). It is more common; however, to bore at breast height. Many site indices (next page) are based on age at breast height. For this reason, age estimates should disclose method including "breast height age" or "total age".