Circular 662

Before making a timber sale, you should know what you have to sell: how much you have and about what it is worth. A professional forester can advise you on which products you have and can also give you estimates regarding the amount. In most cases the forester’s experience with timber sales and his knowledge of the current markets can increase your revenues far in excess of his fees. If professional services are not available, however, you can follow a few basic techniques to roughly identify and estimate the forest products on your land.

Basic size criteria of trees are diameter at 4.5 feet above the ground (DBH) and height. The height, in feet, may be measured as total height in some instances. In others the merchantable height, or the distance to some specified top stem diameter, is needed. Both measurements can be taken with a scale stick, available from most forestry supplier companies, but there are other ways.

Simple calipers for measuring the diameters of trees can be made from a framing square and small wooden strips (Figure 1). Heights can be estimated by leaning an 8- or 16-foot pole or strip next to the tree and judging how many 8- or 16-foot lengths are in the tree.

Certain hardwood species in Florida may be sold for pulpwood, sawtimber, and veneer. Markets for pine include pulpwood, chip-n-saw, sawtimber, plylogs (or peelers) and poles (Table 1). The diameter limit for both hardwood and pine pulpwood is 4 inches at the smallest end.
Table 1. General standards for southern forest products

Product	Relative Value	Minimum Tree Characteristics
Product	Relative Value	DBH	Merchantable Height	Form
Pulpwood	Low	4"	16' to a 4" diameter	Relatively straight
Chip-n-saw	Intermediate	8"	16' to a 6" diameter	Straight, few large branches
Sawtimber	Intermediate	10"	16' to an 8" diameter	Straight, few large branches
Plylogs	Intermediate	12"	17' to an 8" diameter	Relatively straight, few large branches
Poles	High	10"	35' to a 7" diameter	Very straight, few branches, small branches

Pine chip-n-saw products are trees that will produce some dimension stock (generally 2 by 4s) by means of a special type saw. In the process the wood that is chipped away to make the dimension stock is used for pulp. Chip-n-saw trees must be 8-inch DBH with at least 16 feet of trunk before reaching a top diameter of 6 inches.

To qualify for sawtimber (either hardwood or pine) a tree must have a diameter greater than 10 inches and at least one 16-foot log, 8 inches or larger at the small end.

Although not common in Florida, there is a veneer market for yellow poplar and other mixed hardwoods. Diameters must always measure at least 12 inches DBH and the minimum log length is 16 feet. Pine peelers or plylogs are processed similar to hardwood veneer logs. Unlike hardwood veneer which is used in the furniture industry, the pine is used for the manufacture of plywood.

Pines furnish the bulk of the southern and eastern pole timber. To qualify as a pole, the tree must be very straight with only a few small branches. It must have at least a 10-inch DBH and 35 feet of relatively clear trunk to a 7-inch top diameter. Pole identification and valuation is difficult. Generally, a stand must consist of a good proportion of large, straight, well pruned trees to be considered for a pole cut.

SMALL SIZED PRODUCTS -- Cubic Feet or Cords

The volume of small trees, usually sold for pulpwood, is expressed in cords. A standard cord, or rough cord, is equivalent to a stack of wood measuring 4' x 4' x 8' or 128 cubic feet. However, much of a 4' x 4' x 8' stack is wood, bark, and air space. The actual wood contained in a 4' x 4' x 8' stack is approximately 90 cubic feet. Volume tables can be used to approximate the cubic foot content and, consequently through conversions, the cord content of an individual tree. The table figures can be general or specific regarding tree species and the size criteria used to develop it. In Table 2, the cubic foot volume is expressed in terms of diameter at breast height in inches, and total tree height in feet. This volume table was developed for use with slash pines in north Florida.

To use the table, locate the diameter of the tree in the column on the left. Read across until you reach the column that represents the total height of the tree. For example: an 8-inch DBH tree with a total height of 70 feet will yield 11.805 cubic feet. The cubic feet divided by 90 results in the volume in terms of cords.

Another, but less accurate, way to approximate the pulpwood yield in cords is by using Table 3 (Smiley, W.L. 1969).

Table 3. Number of trees of different diameters required to make a cord.

DBH in inches	# Trees / Cord
7	16
8	11
9	8
10	6
11	5
12	4
13	3

The volume of large trees for sawtimber, poles, or plylogs is expressed in board feet or the equivalent of 1" x 12" x 12" units of lumber that can be cut from a tree.

To estimate the number of board feet in logs of different sizes, log rules are used. A log rule is a statement, either in the form of a printed table or as marked on a measuring stick, of the estimated board feet of lumber that can be sawed from logs at various lengths and diameters.

Board foot products in Florida are normally estimated by the Scribner or the Doyle log rule. Scribner is the most commonly used for pine sawtimber, poles, and plylogs, while Doyle is more commonly used for hardwood sawtimber and veneer. The Scribner rule is probably fairest for buyer and seller of southern timber, where most of the timber cut would be logs smaller than 20 inches in diameter. Similar to the cubic feet volume tables, board foot tables have been developed for specific locations and tree species. Table 4 is a general Scribner board foot volume table constructed from diameter and usable 16-foot log size criteria. The table is used in the same manner as the cubic foot table previously discussed, with one exception. For exceptionally tall, slender trees, add 10 percent of the given volume and deduct 10 percent of the given volume for stocky, tapered trees.

WEIGHT

A more recent and quite common way of purchasing forest products is by weight. This measure tends to add another level of confusion for many landowners who are not familiar with the forest products industry.

As among people, the weights of similarly sized trees will vary. Consequently, the weights of cords and board feet will vary from species to species, seasons and location of harvest, differences in growth rates, and the length of time between harvesting and weighing in at the mill or scale site. Table 5 shows the differences in weights of cords among species and the difference between air-dried and green weight of a cord of the same species. Average weight conversions for the most common forest products are listed in Table 6.

Table 5. Average weights of a standard cord (128 cubic feet) of pine pulpwood for various species Table 5. Average weights of a standard cord of pine pulpwood for various species

Table 5. Average weights of a standard cord of pine pulpwood for various species

Table 6. Weight conversions for common forest products in the southeastern United States

Now that you know the basic concepts of measurements and yield units you can begin to think about your wooded areas in terms of what you have and how much there is of it.

STEP 1 -- Type Map

Prepare an inventory or type map of your land to define each general land-use category. The land-use categories or forest-types can be identified readily from an aerial photograph of your property.
In most cases your county Soil Conservation Service (SCS), Agricultural Stabilization and Conservation Service (ASCS), or the Florida Division of Forestry will provide services to help you construct the map similar to the one in Figure 2.

Figure 2. Forest type map taken from aerial photograph showing roads, property, and vegetation boundaries.

STEP 2 -- Determine Acreage

Determine the amount of acreage in each forest-type. A plastic template called a “dot grid” facilitates this calculation. In most cases the ASCS, SCS, or Division of Forestry Office will have instruments to help you calculate the acreage.

STEP 3 -- Select Sample Size

Decide how much of each type should be measured. The yield of a stand is usually impossible to calculate by measuring each tree. Typically, a portion of the stand is measured, and the results of the measured trees are expanded to represent the entire stand. The degree of sampling (the percentage of the stand to measure) depends on the size and uniformity of the area to be measured. When time is short or the forest large, the owner may have to judge the yield of his whole stand by the part he has time to measure. It is important to get a fair sampling, neither better nor worse than the rest of the forest. In general, the higher the value of the timber, the larger the sample should be.
For measurement purposes, pine stands may be classified into two categories -- planted stands (plantations) and natural stands, or those that were established by natural conditions.
Generally, young planted stands, less than 20 years old, are uniform in stocking (number of trees per acre), size (diameter and height), and site or soil characteristics. If great differences in any of the three characteristics are not obvious, the yield of the stand may be estimated by measuring several trees to calculate an average diameter and height.
As planted stands mature, obvious size differences among the individual trees begin to show. Because of competition for space, nutrients, moisture, and differences in growth rates of individual trees, an older planted stand may begin to take on characteristics of a natural stand.
The exact percentage of the stand that is needed for a sample will vary according to the precision that is required, the conditions of the stand, and the types of forest products that may be present. If a stand has many trees that could be sold for poles, a high value product, a higher percentage of the stand should be measured.
General guidelines for the percentage of natural stands to measure, or mature planted stands that are not uniform, are listed in Table 7.

Table 7. Approximate percent of stand that should be measured in relation to stand area

Stand Area (Acres)

Percent Measured

10 100

11 - 25 33

26 - 50 20

51 - 100 10

101 - 500 5

501 1

STEP 4 -- Select the Best Inventory Method

There are many different inventory methods that may be used to measure the sample areas. The appropriate method depends on the characteristics and conditions of the stand. An experienced professional forester is best qualified to judge the appropriate method; however, there are some general selection criteria.
A strip cruise method may be useful for a high percent cruise. To implement a strip cruise all the trees in a narrow strip are measured. The number of strips that are run through the stand depends on the width of the strip (usually determined by the stand boundary), and the number of acres that are to be measured.
For example, on 50 acres of mature pine with several different sized trees the recommended minimum area to sample is 20 percent or 10 acres. The equivalent of one strip 66-feet wide by 6,600-feet long must be measured. The property boundaries may not accommodate a strip 6,600-feet long; therefore, it will be necessary to run several strips on uniform spacing that will equal the distance needed. Strips should be located to run with the slope; that is, if the land slopes from north to south the lines should run from north to south.
In large stands composed of relatively small sized trees the fixed area plot is used. The fixed area may be circular or square, but the size of the plot, in terms of area, depends on the uniformity and age of the stand, and the amount of time it takes to locate plot centers. Obviously, the larger the plots, the fewer needed to measure a given area. The plot size that generally includes 8 to 15 measurement trees is the best size to use. Table 8 shows dimensions for different sized plots.
On 50 acres of planted pines that are relatively small and uniformly spaced the recommended sample area is 10 percent or five acres. Using 1/20-acre plots, 100 plots must be measured to equal five acres of sample area. These plots must be uniformly located across the entire 50 acres in order to get a fair sampling.

STEP 5 -- Tally the Plots

Two types of forms may be used to record the trees that are measured in the sample plots. Examples of these forms are shown in Figures 3 and 4.

The dot notation is a convenient way to record the number of trees measured. This system is illustrated in Figures 3 and 4. One dot represents one tree in a particular diameter and height category. Additional trees in the same category are represented by additional dots until a square is formed by the four dots -- this cluster represents four trees. The fifth tree is represented by one line connecting two of the four dots. The line connecting other dots in the cluster is used to record additional trees until a square is formed by the lines. The square, which is a result of four dots and four lines, represents eight trees in that category. Diagonal lines, forming an “X” in the box, represent 10 trees. Additional trees in that category are recorded using the same system to begin a new cluster.

STEP 6 -- Summarizing Sampling Records

To summarize the sample measurements a summary table is constructed from the information on the tally sheet and a volume table. A summary table must be made for each separate product that was measured in the sample plots. Figure 5 represents a summary table for the pulpwood tally sheet shown in Figure 3. A blank tally sheet, with the addition of a “sub-total” column, may be used.

Figure 5. A summary sheet indicating cubic feet volume for each size category of trees measured in the sample.

The number in the first size category (6-inches DBH and 20-feet total height) is a result of multiplying the number of trees in that category (2) by the number of cubic feet that a tree of that size can be expected to yield. The cubic foot estimate of one tree 20 feet tall and 6 inches in diameter (1.078) is found in Table 2. Therefore, the estimated volume of the trees in the sample that fell into the 6-inch DBH and 20-foot height category is:

Number of trees in size class
X Volume / tree
= Volume / size class

2 1.078 cu. ft. 2.156 cu. ft.

Each block in the table is calculated in the same manner until all volumes for all size classes or categories have been entered into the table. The cubic foot volumes are then summed across the page by DBH class, or down the page by height class. In this particular example the category volumes were summed across the page first and then down the sub-total column to give the total volume obtained from the sample.

STEP 7 -- Convert Sampling Estimate to Cords

The total cubic feet which resulted from the sample measurements should be converted to cords by dividing the total by 90 cubic feet. In this example the number of standard cords in the sample is:
3,490.87 cu. ft./ 90 cu. Ft./cord = 38.787 cords in sample.

STEP 8 -- Convert to Cords / Acre

Suppose the measurements represent a five percent cruise of a 30-acre stand of planted slash pine. Assuming this, the actual area measured was .05 X 30 acres or 1.5 acres. Therefore, the cords in sample (38.787) divided by the acres in sample (1.5) equals the estimated cords per acre (25.858 in this example).

STEP 9 -- Calculate a Market Value

As with any commodity the market value will vary considerably based on the amount of the product to be sold, the season, the accessibility of the forest, distance to the mill, and the terms of the individual sales contract. Monthly price and markets reports are published in the School of Forest Resources and Conservation Extension Update newsletter. Also, current and historical price information is available through the IFAS-VAX computer network system which can be accessed from many county extension offices. While the stumpage prices shown in these references do represent actual sales, keep in mind that individual sales may bring higher or lower prices.
To convert your estimated cords per acre to actual dollars, select a stumpage price that appears reasonable for your local area. Multiply the estimated cords per acre by the stumpage price. In this example $25.00 per cord price was selected; therefore the stumpage value (money paid to you as the trees are standing in the forest) is:
25.858 estimated cords/acre X $25.00 estimated price/cord = $646.47/acre

Now that you see the relative value of your forest crop keep in mind the following points:

The exercise you conducted was crude, at best, and it may not be an accurate assessment.
There may be other volume tables which you are not aware of that more closely represent the amount of wood on your property.
You may have selected an inappropriate sample size.
The terms of your individual sales contract and the conditions of your forest may prevent your selling price estimate from being realistic.

Because timber investments do involve considerably longer turnovers, as compared to other agricultural commodities, many individuals do not experience frequent sales. Consequently, many landowners may not be aware of the value of their forest.

The purpose of this exercise was to inform you of the complexities involved in trying to set values on your forestry investment. Forestry is a business and should be treated as such.