What is a 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 article will help you to answer these important questions.
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
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Forestry Services
1 – Land Measurements
- chaining horizontal distances
- pacing horizontal distances
- using a compass
- using topographic maps
- a simple closed traverse
- tree diameters
- tree heights (merchantable vs. total)
- tree age
- tree form expressions
- using yield and volume tables
- statistical concepts
- common sampling designs
5 – Estimating Site Stocking and Density
Before the Cruise
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 Recce
Dig out your records and make sure that the location and size of your area are clearly specified. Walk the boundaries as they are described on the map and be certain that they are clearly marked.
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.
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.
Sample Size
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.
Information
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.
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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.
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An important part of the cruise is an evaluation of the soil. 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 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.
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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.
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The cruise should include a written report on stand conditions, particularly for areas that need cultural treatments or are ready for harvest. These areas should be shown on the map.
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The information gathered in your cruise may shape the goals and objectives you formulate for your forest land. The broader the range of information you get in your cruise, the richer an understanding you will have of the conditions on your property. This understanding will help you make sound decisions about the long-term management of your land.
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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.
Concluding Remarks
- 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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For correction and improvements please use the comments section below.
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