Forest inventory

Forest inventory is the systematic collection of data and forest information for assessment or analysis. It is also commonly known as timber cruising. It is important for owners to "cruise" the timber to get an estimate of the value and possible uses of the timber. When taking forest inventory the following are important things to measure and note: species, diameter at breast height (DBH), height, site quality, age, and defects. From the data collected one can calculate the number of trees per acre, the basal area, the volume of trees in an area, and the value of the timber. Inventories can be done for other reasons than just calculating the value. The timber can be cruised to determine potential fire hazards and the risk of fire. The results of this type of inventory can be used in preventative actions and also awareness. Wildlife surveys or inventories can be taken to determine the number and type of wildlife within a forest.

History

Surveying and taking inventory of trees originated in Europe in the late 18th century out of a fear that wood (the main source of fuel) would run out. The first information was organized into maps used to plan out usage. In the early 19th century foresters estimated the volume and stocking of smaller forests with their eyes. Larger forests were divided into smaller sections that were individually estimated by visual inspection. The estimates were added together to figure out the entire forest’s resources. As the 19th century progressed so did the measurement techniques. New relationships between diameter, height, and volume were discovered. These newfound relationships allowed for a quicker assessment of much larger forests. By 1891, the surveys were conducted through sample-based methods involving statistics. In the 20th century, the statistical method of sampling had become well established and commonly used, and better methods, such as unequal probability sampling, arose. As the 20th century progressed and the new technology of computers and computer data-basing became available, sampling and assessment became more efficient.

Stand Examination

Today, the most common type of inventory is one that uses a random sampling technique which groups similar forests into one category based on age, stand structure, species, and location. The next step would be to begin from a random place and measure circular plots that are equally distanced. When taking inventory, a decision has to be made about which types of plots to measure. There are several different types of plots. Yet, there are two common types: "fixed radius" and "variable radius" also known as "prism radius". In a fixed radius a plot, the forester finds the center of a plot and every tree within a certain distance away from that point is measured. Variable radius plots are used more for inventory of volume. During this method, a angle is created and projected from the plot center and all trees that are larger than the projected angle are measured.

References

[http://fennerschool-associated.anu.edu.au//mensuration/history.htm] Brack, Cris L. “A Brief History of Forest Inventory.” History of Inventory. 27 Mar. 2008]

[http://www.cnr.berkeley.edu/departments/espm/extension/INVENTOR.HTM] Leblanc, John W. "What Do We Own: Understanding Forest Inventory." Working in the Woods. University of California Cooperative Extension. 28 Mar. 2008]