Dokładność sposobów określania miąższości dłużyc bez kory według normy PN-D-95000:2002 na przykładzie sosny zwyczajnej (Pinus sylvestris L.) z terenu Nadleśnictwa Płaska

The State Forests, National Forest Holding operates on the principle of financial independence, and the sale of wood is the primary source of income of the institution. Raw wood is sold with the bark, although the registry applies to the wood without bark. It was hypothesized that the method of bark volume reduction may have a significant impact on the registered volume. The material collected in the Płaska Forest District was used to assess the impact of method of bark volume reduction presented in the PN−D−95000:2002 standard on the volume of Scots pine logs in thinned and harvest stands growing on fresh coniferous forest habitat. Analysis of the accuracy and precision of each method were carried out on the basis of sectional measurements of 180 logs (90 per stand type). Four methods were compared: table deduction depending on the diameter of the stem (method 1), measurement of bark thickness with manual bark gauge (method 2a), mechanical removal of the bark using a spokeshave at the place of measurement (method 2b), and calculation of the log volume with Huber formula and subsequent subtraction of the bark volume determined based on special ratio (method 3). All methods caused negative systematic error, and thus have a constant tendency to underestimate the volume of Scots pine logs. At the same time, the underestimated log volume varies depending on the method used. To the greatest extent it is lowered using method 1, as it differs significantly from the other methods. Slightly smaller errors are characterized by the method 2a, for which the average error rate also differs from the other methods. The smallest errors are provided by methods 2b and 3, between which we found no significant differences. Analyses indicate that the preferred method of determining the volume inside bark is a mechanical removing of bark, measuring the diameter without bark and calculation of the volume with Huber formula. It is also noteworthy to take into account the deduction percentage of bark in the logs of large−sized wood.