Forest Inventory

What is a forest inventory? Why should you inventory your property? What kinds of information do you need from an inventory? Whom do you ask for assistance in cruising your forest property? This section will help you to answer these important questions.

What is a Forest Inventory?

A forest inventory or cruise determines the location of timber and estimates its quantity by species, product potential, size, quality, or other characteristics. A cruise may be conducted for land acquisition or sale, a timber sale, or other objectives.

A cruise can also assist in assessing other forest values such as wildlife habitat (mast, crops, snags, wetlands, dens, nests, thickets, etc.), watershed, recreational opportunities, or other management opportunities that exist on the property.

Why Should You Cruise Your Property?

The reasons for conducting a cruise vary among landowners, and these reasons are dictated by the goals and objectives landowners have for their properties, financial or otherwise. Some common reasons why landowners cruise their forest lands are:

  • To provide a basis for evaluating present conditions
  • To provide a basis for future resource planning
  • To provide a basis for planning property insurance needs
  • It is a valuable aid in any property settlements and rental agreements
  • It is necessary in the preparation of a net worth statement
  • It is necessary to be sure that you are claiming the proper depreciation for income tax

Do any of these reasons apply to you? If so, a timber cruise may be the next order of business on your property.

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Forestry Services

Whatever the reason is for your decision to cruise your land, the next step is to decide who will conduct the cruise. Depending on your personal experience, you could conduct the cruise yourself. If you do it yourself, you should at least have experience with the following:

1. Land Measurements

  • chaining horizontal distances
  • pacing horizontal distances
  • using a compass
  • using topographic maps
  • a simple closed traverse

2. Measuring Standing Trees

  • tree diameters
  • tree heights (merchantable vs. total)
  • tree age
  • tree form expressions

3. Volume Calculations

  • using yield and volume tables

4. Sampling and Estimation

  • statistical concepts
  • common sampling designs

5. Estimating Site Stocking and Density

consulting foresterIf you don't have experience with these, you should probably use the services of a forestry professional. One of the most important forestry professionals is the consulting forester. Before choosing a consulting forester, do some research on the consultants in your area. Talk to other clients and people who have known the consultants from long business experience. Managing forest land is a highly technical and long-range endeavor. You need the best possible assistance.

Resources

These useful Extension publications providing detailed information on the types of forestry professionals available. Some information on assistance programs is also given.

See the Consulting Foresters page in the Directory for contact information.

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Before the Cruise

Whether you decide to use the services of a professional forester or to do it yourself, there are some things that you should do before the cruise to make sure all the background information is in order.

Get a Map

If you don't already own a map of your property, get one. Your county courthouse, library, or a surveyor's office are good places to find the information needed to obtain the appropriate map which shows your property. If your property is small, the section of the map showing your property can be blown up to a more convenient scale.

Do Some Walking

Dig out your deed and make sure that the location and size of your property is clearly specified. Walk the boundaries as they are described in the deed and be certain that they are clearly marked. This will prevent accidental trespass and potential conflicts with adjacent landowners.

While you are out walking the boundaries, take some time to become familiar with your land if you haven't done so already. This can be a very rewarding experience, especially if the family is involved. Going out and learning about the forest firsthand may be the beginning of a growing interest in forest management and stewardship for you and your family.

pineTake a few days to go trekking around your land with the map of your property, a compass, and some field guides on the plants and animals of your region. Note any specific details such as water bodies, large trees, wildlife habitat, hazards, or any other sites of significance on the map. After a thorough informal survey of your land, write a brief description of your findings. Forest landowners who know their land well are equipped to take an active role in formulating goals and objectives for their land, and in developing and carrying out forest management plans.

Compartmentalize the Land

If your forest property is large (over 300 acres) and contains several different forest types based on site characteristics, species, and stage of tree growth, it may be necessary to organize your property into specific compartments or management units. Why would this be necessary?

  • Some stands require specific management activities.
  • Some stands have greater timber-producing potential than others.
  • This makes it easier to keep financial and work-progress records.
  • It may be necessary to keep records for tax purposes.

Aerial Photographs

An aerial photograph of your land will help you determine the types of forest communities you have and to organize your property into compartments if necessary. A professional forester can assist you in obtaining and analyzing aerial photographs.

If it is necessary to organize your property into compartments, each compartment should be cruised separately. This will promote more uniform data from the cruises, thereby making the analysis less difficult. Also, more accurate and specific information will be provided for each compartment.

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The Cruise

Sample Size

The purpose of the cruise is to find out what you own. This could be done by measuring every tree on your property, but it is often more economical to measure an adequate sample of the trees. What is important for you as the landowner is to be sure that the sampling percentage is large enough to give you a reasonable estimate of what you own.

The size of the sample will depend on the total area, the purpose of the inventory, and the species, size, distribution, and value of the timber. In general, a comprehensive inventory requires a 20% sample for areas under 300 acres, and a 10% sample for areas larger than 300 acres.

For example, if you own 100 acres of timberland, it would be necessary to measure every tree on 20 acres. If the area is 500 acres in size, it would be necessary to measure every tree on 50 acres.

A professional forester will be able to plan an efficient sampling system for your property. See our Directory for a list of consulting foresters.

Information

Once the sampling system is determined, it is necessary to decide how much information to gather. In other words, what do you want to know about your land?

For example, if you want to determine how much pulpwood and sawtimber is on your property, the cruise must show volumes by products, species, or groups of species, and dbh (diameter at breast height (4.5 feet above ground)) classes.

For this information, 2 measurements are needed on each tree sampled:

  1. the dbh
  2. the merchantable height (small end diameter 6-7 inches)

If you wanted to know how many stems of pine regeneration or a particular wildlife food plant there are per acre, the cruise must show how many stems of the plant there are at each plot sampled. For this type of measurement, it is often helpful to divide each plot into quadrants and sample smaller vegetation in terms of percent cover. This information can be used to describe the overall structure of the understory vegetation, which can be translated into wildlife habitat conditions.

Growth Projections

Another important part of some cruises is an evaluation of growth rates for projection of future tree sizes and volume. Growth rates can be determined by using an increment borer. A few trees in each diameter class should be sampled by counting the number of growth rings in the outside inch of the borer sample for each sampled tree.

For example, if there are two rings in the outside inch of a borer sample, it took two years for that tree to acquire an inch of radial growth.

See our Growth & Yield page for more information.

Soil

An important part of the cruise is an evaluation on the soil on your property. The productive capacity among different soil types is variable. Some acres may produce twice as much wood volume as others, and recognizing this could offer you excellent opportunities. The measure of soil capacity used by foresters is called site index. Site index is the total height (in feet) to which the dominant trees in a timber stand will grow in 25 or 50 years.

For example, an acre with a site index of 90, base age 50, will grow a stand of trees in which the dominant ones will be 90 feet tall at age 50. Terms and ages vary with species and geography but the principle is always the same.

See our Soils page in the Forest Resources section for more information.

The USDA Natural Resources Conservation Service has prepared soil surveys by counties for most of the nation. These surveys include detailed descriptions of the soils of the county and a discussion of their suitability for crops, tree farms, pasture, engineering applications, and wildlife habitat. The USDA Service Center in your area can provide you with a survey summary for your county and a consulting forester, county forester, or extension agent can help you understand what the information means to you.

Contacts

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After the Cruise

When the cruise is complete you need to make sure that the information is complete according to your objectives.

The following records should be at hand:

  • a description of the sampling system (technique, sample size, parameters)
  • a copy of all field measurements
  • a summary of tables, by compartment, of tree sizes and stocking
  • a resource analysis report including a map
  • estimates of resource value
  • cost estimates for all phases of the inventory

The storage of this information is as important as the information itself. Make sure you have all computer files backed up and all hard copies duplicated and filed in a safe place.

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Concluding Remarks

Private landowners are a diverse group with many types of goals and objectives for their lands. Regardless of your plans, the sooner you take inventory of what you own, the better prepared you will be to implement or further develop your original ideas.

Keep in mind that a cruise will be most helpful if:

  • it yields enough information for you to make sound decisions about the long-term management of your forest land;
  • it is accurate;
  • the information from the cruise is accompanied by descriptive, qualitative information;
  • the information is available for future reference.

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Resources & References

  • Resources

    References

  • Avery, T.E. and H.E. Burkhart. 1983. Forest Measurements. McGraw-Hill Publishing Co., N.Y. 329 pp.

  • Fazio, James R. 1987. The Woodland Steward. The Woodland Press, Moscow, ID. 211 p.

  • Goff, Gary R. 1994. Timber Management for Small Woodlands. Inf. Bull. 147IB180rev. N.Y.S. Coll. of Agr. and Life Sci., Cornell University, Ithaca, N.Y. 57 pp.

  • Vaardman, James M. 1978. Tree Farm Business Management. John Wiley & Sons, Inc., New York. 213 pp.

  • Vaardman, James M. 1989. How to Make Money Growing Trees. John Wiley & Sons, Inc., New York. 296 pp.

  • Wenger, K.F., (ed). 1984. Forestry Handbook. John Wiley & Sons, Inc., New York. 1,335 pp.

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