Why are there 12 kinds of forests growing in the province? The short answer has three parts: 1) there are a lot of climates in BC, 2) each favors a different assortment of plants, 3) botanists have decided where it is reasonable to draw lines, .... The longer story is one of heat and cold, and mountains towering up for a mile or two. Huge weather systems with storm clouds carry tons of water from the ocean, fall to Earth, and dry air carries away more tons of water from the land. © 1996. Edwards, Y. British Columbia. In R. Kirk (Ed.), The Enduring Forests. Seattle: The Mountaineers, p. 113.

So How Big Are Those Old Growth Trees Anyway?
This photo was taken before the invention of the chainsaw. The ax, the double-bladed ax, and the two-man saw were used to fell these giants. After all the limbs were sawn off by hand, the fallen trunk had to be cut again and again into manageable sections to be moved out of the forest, either by teams of up to 16 oxen or later by "skid roads," or small-gauge railroad cars. Photo: Special Collections Division, Univeristy of Washington Libraries. Negative # UW 13052. Not to be copied or downloaded without permission.

If you have never seen old-growth trees, you may have a difficult time visualizing just how big they are. Even this historic photo of an old-growth tree may not help. The activities below should give you a new perspective on the enormous size of these trees. These activities should provide an awareness of why these trees, containing thousands of board feet of lumber, are so important to the logging industry.

Activities
Most people can easily estimate the length or width of a room, but what about an old-growth tree? Look at the measurements in the table below and mentally test your perception of just how big these old-growth trees actually are. At two hundred fifty-five feet (the height shown for a Douglas fir), would you estimate it to be approximately equal to

• the longest single (straight) hallway in your school?
• the length of the gym or cafeteria?
• or perhaps the distance between goal lines on the football field?

Now, consider the circumference. Could a cross-sectional piece of an old-growth tree fit

• on the stage in your school?
• inside your classroom or cafeteria?
• how many ten-yard lines would it cover on the football field?

Do any of these trees have a diameter wider than a school bus? Is the whale really the largest living thing on Earth?

Data adapted from Olympic National Park Field Guide; The National Park Service; and Redwood National & State Parks

Get a 100-foot or 50-meter measuring tape, and using numbers from Table 1, mark off on your school grounds an area equal in circumference to one of the old-growth trees. Perhaps masking tape could be used on the classroom floor for this purpose. You might use sticks or poles of some kind on a football field or baseball court to mark off the tree's height.

Activity 2
What are the tallest species of tree where you live? Can you figure out their heights? How do the trees in your neighborhood compare in size to the old-growth trees?

Take a walk around your neighborhood, find the tallest tree, and measure its height. Lumber companies and forestry agencies use special equipment such as clinometers, altimeters, or hysometers to measure the heights of standing trees. It is possible, however, to estimate (with a high degree of accuracy) the height of a tree without expensive equipment.

The method of measuring the height of a tree described below is taken from a 1948 Handbook for Boys published by the Boy Scouts of America. Although this method requires no special equipment, you will need a partner, a marker, and a tall pole, perhaps a broom or lawn rake.

Inch-to-foot Method. -Starting from tree, walk eleven steps (or measure eleven stick lengths, or eleven of any other units). Push a stick in the ground at that point. Then measure one "unit" more (step or other unit). Mark that point. Next place your eye as close to that point as possible and sight across the stick to the top of the tree. Note where your line of vision crosses the stick. The distance from the ground to the point where your line of vision crosses the stick, in inches, equals the height of the tree in feet (p. 272).

graphic created using images from www.arttoday.com

NIH Image provides another method to determine the height of standing trees. This photograph is of one of the largest maple trees in a neighborhood in Wheeling, West Virginia. It was scanned and saved as a TIFF file that can be opened in NIH Image.

Considering that most of the homes in that neighborhood were built in the early 1900s, it would be safe to say that it has taken this maple tree approximately 90 years to reach its current stature. How does it compare in height, circumference, and age to that of old-growth trees?

Download TIFF on to your hard drive and open it in NIH Image. NIH Image has a wide selection of measurement options, but before you actually begin making measurements, you will need to: set the scale of the image, and then select the measurement options you want to use. (If you have forgotten how to set scale or make linear measurements, visit beautiful Honolulu and refresh your memory!)

Use the young man standing along side the tree as a scale. He is 6 feet tall. To measure the height of the tree, place the cursor at the bottom of the tree. While clicking and holding down the mouse button, drag the cursor to the top of the tree, and release the mouse button. The line of "marching ants" will appear between the starting and ending points. Select Analyze/Measure and then Analyze/Show Results. A data window will appear showing your distance measurement.

You can also use this image to determine the number of board feet contained in this tree. Again using the young man as a scale, measure the diameter of the tree at breast height, and follow the procedure in Activity 3, below.

If you have access to a scanner, you may want to take a photograph of the tallest tree in your neighborhood to use in this activity. Remember to include someone or something of known height in the picture as a scale reference.

What Is The Economic Value Of An Old-Growth Tree?
It might be interesting to find out what variables determine the price per board foot of lumber, then calculate the economic value of an old-growth tree and compare it to that of commercially grown trees.

Activity 3
An Ohio State University Extension web site provides two tables from which you can estimate the gross number of board feet contained in a given tree. In order to use the tables, you need to know the tree's diameter at breast (Dbh) height and how many 16-foot logs (or 8-foot half-logs) are contained in the tree's trunk. Since you only want a ball-park figure, assume the heights in Table 1 represent "merchantable" heights. Divide the merchantable height by 16 to determine the number of 16-foot logs in a given tree. Note that the tree circumference given in the table is in feet not inches. You will first need to convert the circumference to inches and then divide by 3.14 to determine Dbh.

Now, refer to either of the tables at the Ohio State University Extension web site to find the gross number of board feet contained in a given tree. Information in their web site indicates that the International 1/4-inch rule (Table 2) is used by the U.S. Forest Service and more accurately estimates the yield of lumber than does the Doyle rule (Table 1).

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