How are the felling of forests planned?
Stock survey are made to determine the quantity and quality of wood that can be obtained during forest clearance. The results of the measurements are necessary to develop a strategy for the acquisition and sale of wood for the next year.
The person responsible for setting the deadline for stock survey is the forest inspector, while the valuation itself should be carried out by a person with stocktaking qualifications.
There are several methods of assessing the value of timber:
- the “comparative” method – consists in determining the quantity and quality of assortments on the basis of comparing a group of trees with other similar ones, where the work was carried out in the past and its results are known
- “artificial” method – precise estimation of the quality of each tree by measuring their diameter at breast height and determining their height in relation to thickness classes. This method uses tools such as a caliper, commonly called a clup, and an altimeter. The thickness measurement is made at a height of 1.3 m from the ground surface. Trees growing on slopes are measured from the side of the hill. The result is always rounded down to full centimeters. Speaking of tree height, usually 20 to 30 trees of one species are measured at a distance of 20 m. All measurements, i.e. width, height and wood quality class, are entered into the field report and then entered into the system.
- “mass” method – a method that determines the value of wood on the basis of a forester’s experience
- the “border” method – classification based on the results from previous years for individual stands based on a computer system
During stock survey, signs indicating the quality class and assortment appear on the trees. The symbols used are:
A – sawmill wood of the highest quality class WA0
B – sawmill wood of the high quality WB0 class
F – wood intended for veneer class WA1
S – wood intended for plywood class WB1
Trees classified to other quality classes are marked with a diagonal line in green.
Stock survey is an activity that requires precision and accuracy, because the results are the basis for tenders, affecting the valuation, as well as payments for forest service companies.
In order to minimize the risk of errors, it is important to be meticulous when entering measurements in the record sheet, rounding numbers appropriately and correctly entering the results into the system.
Preparing accurate stock surveys should always be a priority.