Introduction

The professional forester who manages forests for a timber crop must often conduct a volume cruise. The volume cruise is used by loggers who wish to bid on a forest tract that is ready to be cut and taken to the saw mill. A volume cruise tells the logger how much available wood there is in the forest. The logger then decides how much he is willing to pay for the right to cut the trees, and gives the dollar amount to the forester on a piece of paper in a sealed envelope. More than one logging company bids on the forest tract, so the forester has several sealed envelopes with 'bids' inside. After the deadline, the forester opens all the envelopes and looks for the highest bid. The forester notifies the highest bidder that their logging company has won the logging rights to the specified forest tract. After the logging company has cut down the trees, it will sell the logs to a saw mill, who then cuts the logs into planks and boards.

The volume cruise is a very important task performed by the forester. If the volume cruise is not done properly, the logger may end up bidding too much and lose money. If it is underestimated, then the forester loses money. The forester must be accurate in all measurements to reduce the amount of error.

1. Now that you know how to calculate the board footage in one tree, can you perform a volume cruise to estimate how many board feet of lumber are there per acre? (how many thousands of board feet)?

Hypothesis
    Students should make their own before continuing.

Materials

100 foot tape	Plot sheets
Clinometer	20 BAF prism
DBH tape	Compass
Map of forest	Plastic flagging

Data Gathering
As a class, you will decide what data to gather and develop a data table to use.

Procedure

1. Look at a map of the area you are about to 'cruise'. You will be told where the starting point for the transect will be. Mark it down on the map. Your teacher will tell you what compass reading the transect will follow. Write this down. You will be told how many plots will be located along the transect and how many feet are between each plot. Write these numbers down. See figure A.
2. Walk to your starting point and tie some flagging on a tree branch, sapling or a stick driven into the ground. Set your compass to the predetermined azimuth. Stand directly over the starting point and sight along the compass arrow. Pace the predetermined distance along the compass route until you come to the first plot center. Drive a stick into the ground at plot center and tie a flag on it.
3. Standing over the plot center stake, and going clockwise from 0 degrees north, use the 20 BAF prism to determine which trees are 'in' the first plot. See figure B. For each tree that is 'in', measure its diameter and determine how many 'usable' or 'merchantable' (straight and unforked) 16 foot logs are in the tree. See figure C.
4. Standing over the first plot center, sight again along the compass arrow (same azimuth as before) and pace the predetermined distance to the second plot center. Follow the same procedure as you did in #3. Record the results on the second plot sheet.
5. Transfer your information from the plot sheets to the Horizontal Point Sampling Cumulative Tally Sheet. To understand how to do this, look at the example Cumulative Tally Sheet. f = the prism number. You will put 20 in this blank. N = the number of plots used. Look at the point count / tree tally at point box. The 4 next to the 1 means 4 trees were ' in' at plot #1; 10 trees were 'in' at plot #2, etc. Altogether there were 37 trees measured in this example cruise. Note that there are 37 slashes in the DBH/Log grid. If there were 23 trees measured in your cruise, then there will be 23 slashes in your tally sheet. Look at the 12 inch DBH class row. There are zero slashes in the 0.5 column which means there were no trees measured in the entire cruise that had a DBH of 12 with an 8 foot log. In the 1 log column for the 12 inch class, there are 2 slashes which means there were 2 trees in the entire cruise that had a 12 inch DBH and a 16 foot log of merchantable timber. In the 1.5 log (16 ft) column, there is 1 slash which means there was just one tree that had a 12 inch DBH and 1.5 16 foot logs. Altogether in the example cruise, 3 trees out of the 37 had a 12 inch DBH. Now read all the way across the 12 DBH row to the Sum column. The example number is 206 which is the result of adding together the Highest number slashed out from each of the 8 log columns. In this case, 122 was the highest number slashed out from the 1 log column and 84 was the highest number slashed out in the 1.5 log column. 122 + 84 = 206.

The next column to the right is labeled Volume per Acre. In the 12 DBH row, the number is 404. 404 is acquired by multiplying 206 by 1.96. 1.96 results from dividing the BAF number by the number of plots measured. The figure 9,707 at the lower right hand corner of the tally sheet is the board footage per acre that would be expected in any random acre of this particular forest stand.

Blowouts

1. Try to find out how many acres are in your forest tract and multiply the number of acres times the Volume Per Acre total from the tally sheet.
2. Remember that a ranch style house with 3 bedrooms (1000 square foot) would need 3000 board feet of lumber. How many houses could be built from your forest tract?

Plot Sheet

Name ________________________ Group__________________________

Type of Survey	xx	.	Subunit	x	.
Forest	x	.	Stand	x	.
Block	x	.	Elevation	xx	.
Compartment	xx	.	Slope Position	x	.
Subcompartment	x	.	Logged	x	.

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Transect No.

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Point No.

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Tree No.

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Azimuth

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No. of Trees

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Tree History

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Species

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DBH

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#16-ft logs

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Age

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Height

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Crown Ratio

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Crown Class

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Defect Indicators

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Damage

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Tree/Crown Class

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Mgt. Tree

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GST

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Down Tree

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6.8' Plot

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Branch intersect

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Duff

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Second duff

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27.2' Plot

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Rotten 3"+

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Rotten 3"+

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Slope

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Aspect

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Habitat type

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Background Information
A volume cruise is one of the most important activities of the forester. The Forest Service is a branch of the USDA (United States Department of Agriculture). Since trees are considered a crop which can be harvested, foresters are therefore, the caretakers of the crop before it's harvested. Loggers are the harvesters of forest trees. When a forester decides a tract of forest is ready for harvest, it is put up for bid. Loggers make a bid for the forest tract where the highest bidder wins the right to cut and haul off the trees. However, before a logger can make an accurate bid, he must know approximately how much lumber is on the stump within the forest tract. It is the responsibility of the forester, to conduct a volume cruise to determine the amount of lumber the logger can expect. The volume cruise gives an estimated amount of lumber, expressed as board footage. The volume cruise also gives the logger an idea of what kind of tree species are on the tract, as certain trees are more desirable than others for lumber production.

Target Group
Sixth through eighth grade.

Timeline
This could be a culminating experience for the group where several days could be allotted for completing the volume cruise.

Student Learning Objectives
Students will be able to:

1. Understand the purpose of a volume cruise.
2. Locate a forest tract and determine a compass azimuth for a transect of sample plots within the forest tract.
3. Pace a determined distance to locate random sample plot centers.
4. Use a BAF prism to determine trees that are 'in' the plot.
5. Use a clinometer and DBH tape to calculate the BF (board footage) of 'in' trees.

Preparation and Teaching Tips
The teacher decides what data each class has the ability to successfully collect and build a data table accordingly. A copy of The Horizontal Point Sampling Cumulative Volume Tally Sheet is included.

Procedure
Obtain a map of a forest or forest preserve. Draw a circle around a distinct forest segment. Mark a point on the circle that would be the easiest place to use for a starting point. With a compass and the map, determine a direction (compass degrees) that would go through the middle of the forest tract from the starting point. Decide how many plots should be used, and how far apart the sample plots should be. Two hundred feet is a reasonable distance between plots, but the distance can be shorter if the forest is small. Two to three plots would certainly give the students a "taste" of what a volume cruise is like. Four to five plots would take approximately four hours.

Next, walk to the starting point. Randomly select a tree branch or sapling and tie a ribbon on it. The ribbon will represent the actual starting point. From the ribbon, students will pace out 200 feet along the predetermined compass reading. It would be helpful for students to have already developed a pace of their own. To do this, lay out a 100 foot tape on the ground for students to walk (pace) from 0 to 100 feet and count their steps in between. Have them do this several times till they come up with a consistent number. (Developing contests is a fun activity while students develop pacing accuracy. The teacher picks out landmarks for the students to pace to and then measures the distances to see which student was most accurate.)

When the student reaches 200 feet at the compass reading, the student places a stick at the 200 foot mark and ties a ribbon to the stick. This designates the plot center. Turning clockwise, from zero degrees north, use the BAF prism to designate the number of trees that are 'in' the sample plot. For each tree that is 'in' the sample plot, measure its diameter at breast height (DBH) and its total height. Record these measurements. Trees less than 5 inches DBH are not counted, neither are dead trees. If 4-5 students can be grouped together, the heights and diameters can be done simultaneously, or measurements can be double checked.

Have students calculate the board footage for each tree or choose tree #1 in each plot. If you are really energetic and enthusiastic, use the Horizontal Point Sampling Cumulative Volume Tally Sheet to determine the total board footage per acre in your forest. Try to estimate the number of acres in your forest. Instead of total tree height, you need to determine how many merchantable (usable) 16 foot logs are in each tree that is 'in' the plot. The example given on the Tally Sheet is 5 plots with a 9.8 factor prism, each diameter class Sum would be multiplied by 1.96 (see student procedure). So if your students used 3 plots with a 20 factor prizm, each diameter class SUM would be multiplied by 6.67.

Record the location of your starting point and compass reading for a follow up cruise the next year.

Blowouts

1. There is no way of ever calculating the exact board footage in a given forest because of the sheer numbers of trees and lack of time. Sample plots therefore become an efficient means to "estimate" a calculation. Sample plots are random measurements which are intended to accurately "represent" the whole. The more sample plots, the better the representation. Have the students randomly select another starting point and compass reading to record another set of sample plots (same number) and compare the board footage to the first transect line.
2. Have the students select another starting point and do just one sample plot to compare board footage to a 3 plot transect. Was the one plot a good representation?

Glossary
forest harvest: the periodic removal of usable trees for the purpose of paper, lumber, poles or wood derivatives.

azimuth: a compass direction such as 120 degrees southeast.

transect: a straight line that predominately bisects a given unit.

forest tract: a distinguishable forest area noted for its uniform distribution of tree species and spatiality of trees.

References

1. Manual Of Forest Mensuration. Beers, T. and Miller, C. T & C Enterprises, West Lafayette, Indiana. 1993.
2. A Long Range Plan for Illinois Forest Resources. Illinois Council on Forestry Development. Sept. 1990.
3. Even-Aged Silviculture for Upland Central Hardwoods. Agriculture Handbook 355. USDA Forest Service. Dec. 1968.
4. Stand Examination Procedures. USDA Forest Service Intermountain Region.