Bark Thickness Along Stems of Pine. Functions for Determination of Diameter Under Bark

1990

41 S.

19 Abb., 9 Tab., 8 Lit. Ang.

Unselbständiges Werk

200034015

For the use of bucking algoritms in modern shortwood harvesters or at stemterminals the diameter on bark is measured. To get the diameter under bark, which is required, functions of bark thickness are applied. The logs are delivered to sawmills after bucking. When scaling of sawtimber the diameters on bark are automatically scanned. Also at the sawmill a function of bark thickness is applied to get the diameter under bark as this is the measurement on which the prices are based. The uncertainly as regards precision and accuracy in applied bark functions is the background for this work. Four stands in the region Uppland - Vaestmanland were selected in cooperation with Maelarskog, the local forest owners association. In each of these stands 50 pine trees, Pinus silvestris, were measured with respect to bark thickness along the stem. The functions found to give the best description of the taper of the bark were: (Formel). The literature indicates that it is very difficult to acquire general functions of the bark taper along a pine stem. The problem is mainly varia- tions in distance to where the transition of rough to smooth bark occurs. The aim of this study were primary to derive a function of bark thickness when only knowing the distance from root and diameter on bark. It was assumed that these variables automatically could be registrated in a harvester. For three of the stands the best functions were almost the same while the fourth stand gave quite different constants. The fourth stand was especially significant in site. The acquired function can be applied today in the region Vaestmanland - Uppland when harvesting. Before using the function in other regions more studies have to be carried out. As the place were the transition of rough to smooth bark occurs is shown to be so important for the application functions it might perhaps be wise to approach the problem in another way as has been done in this investigation. It might be best trying to find functions for estimation of height to bark point. After that, other functions could be applied in the different sections. For example a constant could be applied for smooth bark. Finally it has to be pointed out that it must be important in the future to use the same functions for bark thickness in bucking and in scaling timber at sawmills. The price value is based on the scaling at sawmills.