DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
| ŠUMARSKI LIST 9-10/2023 str. 40 <-- 40 --> PDF |
applying Smalian’s formula. The real merchantable wood volume of the tree (vr) is obtained by summing the volume of the trunk and large branches. vr = vtrunk + vlarge branches vtrunk = – Smalian’s formula/trunk subdivides into n sections (wood + bark) – Smalian’s formula vlarge branches vlarge branch (wood + bark) vlarge branch = g1/2 ˙ vlarge branch – Huber’s formula Note: g0, g1, g2… gn is a cross-sectional area at the lower and upper end (m2); g1/2 is cross-sectional area at the midpoint; 0.0033 is a cross-sectional area for a diameter of 7 cm (m2); l is a section length (l = 1 m); lt is the length of top section; vr is the real merchantable wood volume of tree (m3); vtrunk is the volume of the trunk (m3); vt is the volume of top section (m3) and vlarge branches is the volume of part of the branches (m3). Before processing the data, a detailed analysis of the sample was undertaken, checking each tree individually. The trees without visible damage are considered for modeling volume tables. The trees with severely deformed trunks and forked trees are not considered for modeling. In addition to logical control of data, visual control based on the photos of trees and the methods of statistical analysis were also used. After the first stage of sample control, the data was entered into the created database in Excel. Logical control of the entered measurement data was carried out and the necessary corrections were made. In the end, a final sample of 2,413 trees was obtained for the development of regression models. Model trees for the creation of regression models were felled in the following forest management areas: „Posavsko“, „Dobojsko-derventsko“, „Usorsko-ukrinsko“ and „Gornje-drinsko“. In the aforementioned forest management areas, the trees were felled in 19 stands or sub-compartments, which were distributed in 7 forest management units (Figure 1). With a focus on the distribution of oak forests, it is evident that the sample is representative in terms of the spatial distribution of model trees. When it comes to management classes or types of forests, there are three types of forests in the aforementioned areas (Table 1): – Forest type A: High sessile oak and European beech forests on deep acidic brown and ilimerised soils on acidic silicate and silicate-carbonate rocks, – Forest type B: High sessile oak forests on deep soils on peridotite and serpentinite, and – Forest type C: High sessile oak forests on predominantly deep distric brown soils on limestone and dolomite. According to the chemical composition of the bedrock and the reaction of the soil, there are both acidophilic and basophilic sessile oak forests in the aforementioned areas. It can be concluded that the sample is not completely representative when the data is compared with the typological classification of forests in Bosnia and Herzegovina (Stefanović et al. 1977), because trees from mixed sessile oak and Scots pine forests are missing. Table 1 also shows the distribution of the number of model trees by altitude. The distribution of model trees by altitude coincides with the distribution of high forest areas by altitude according to the data of the state forest inventory in the period from 2006 to 2009, according to Dukić (2014). According to Laar and Akca (2007), the standard volume table uses both diameter at breast height and tree height as table entries. Several studies, however, indicate that the addition of a third predictor variable, such as a height above the ground of the base of the live crown (Nåsslund 1947) or stem diameter at 30% of the tree height (Pollanschütz 1965) or at a height of 7m (Winzeler 1986) reduces the amount of unexplained variation and makes it possible to estimate the tree volume more accurately. A larger number of independent variables ensures greater accuracy of the data in the tables, but also complicates their practical application. A large number of models have been tested that has a wide application for equalizing the merchantable tree wood volume as a dependent variable in terms of a diameter at breast height and height of the tree as independent variables [1-6]. In addition to the two-entry models, three three-entry models were tested, namely the model [7] for equalization of the merchantable oak wood volume depending on diameter at breast height, tree height, and diameter at seven meters high used in Switzerland, and two models [8-9] for equalization of the merchantable wood volume of trees depending on diameter at breast height, the height of the tree, and a height above ground at the base of the live crown |