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Advances Made in Improving Timber Inventory Assessments

Accurate and precise timber inventory assessments are critical to good harvesting management and an important part in the process of a forest owner having confidence that he is extracting the maximum possible value from his forest. For stumpage sales, a robust and reliable timber inventory is the means by which the purchaser can offer a fixed price for the forest without having to factor in a big discount for the risk associated with log grade mix and total timber yield.

Since timber inventory assessments are based on sampling a forest (or more correctly a stand) with plots, the inventory will only be accurate if the plots are located such that the trees they include are truly representative of the whole stand. Forests grow differently at their edges due to more exposure to wind and light; this is known as stand edge effect. Stands have highly variable proportions of edges depending on their shape and size and frequency of gaps.

Trees grow very differently within a stand compared to on the stand edge where branches and stem diameter are larger. New sampling design at PF Olsen is ensuring representative sampling of stands and more accurate timber inventory assessments.

Experience has shown that the standard industry practice of systematic-random sampling can result in an inappropriate representation of the stand edge and an inaccurate inventory assessment.

PF Olsen has addressed this issue in its inventory sampling design (i.e. plot locations). Rather than FIPS-GIS (the computer-based crop management system) "laying" different grid orientations over a stand until the desired number of plots is generated, the system is now programmed to measure the amount of stand edge and ensure that it gets the correct proportion representation of plots. This way we gain a higher level of confidence that the inventory assessment will be truly representative of the stand as a whole.

This new innovation will mean forest owners, harvesting managers and log marketers, and forest and stumpage purchasers will have better information on which to base their decisions, and this will assist in extracting the maximum possible value from the forest investment.

Dave Crawley (pictured left), PF Olsen's Resources and Inventory Manager has been involved in the new stand edge sampling process.