In wood production not only the quantity is important but also the quality of wood is of increasingly growing importance. Higher-quality wood has the higher utility value and price. Relatively great attention is paid to these issues in Slovakia. In the past models of tree and stand assortment tables were constructed for 8 commercially important tree species, namely for spruce, fir, pine, oak and beech (Petráš, Nociar 1990, 1991, and for larch, hornbeam and birch (Mecko et al. 1993). Together with the models of yield tables (Halaj et al. 1987; Halaj, Petráš 1998) they were also used for the construction of assortment yield tables (Petráš et al. 1996), and together with the prices of wood and costs of wood logging also for the construction of the models of value production (Halaj et al. 1990). After a short break research on the production of poplar clones Robusta and I-214 continued, Mecko (2001, 2005) elaborated the volume production of these clones in the form of models of yield tables. The research of these authors on the production quality started by the construction of tree assortment tables (Petráš et al. 2007) and continued by constructing stand assortment tables.The aim of the paper is the construction of the models of stand assortment tables for poplar clones Robusta and I-214. MATERIALS AND METHODSWe used the methodology of simulation by means of partial models, namely the following models: -Tree assortments tables, -Uniform height and volume curves, -Probability density function of diameters. Models of tree assortment tablesModels of Petráš et al. (2007) were used. They give the proportions of assortments in percent (quality and diameter classes of logs) in dependence on tree diameter d, stem quality qua and damage to stem dam according to the relation: The results obtained in research on the quality of raw timber by means of the structure of assortments for the stands of poplar clones Robusta and I-214 are presented in the paper. Models for an estimation of the structure of basic assortments of poplar stands were constructed separately for each clone in dependence on mean diameter, quality of stems, and damage to stems in the stand. The clone Robusta has higher proportions of higher-quality assortments than the clone I-214. The accuracy of models was determined on empirical material. It was confirmed by statistical tests that the models did not have a systematic error. The relative root mean-square error for main assortments of the clone I-214 is 15-27% and Robusta 13-24%.
Quality production of wood raw materials with maximal use of natural factors and minimum costs of human labour is the main aim of forest production with regulated management, it means forest cultivation in its whole production framework. Knowledge of the value production of forest stands exists on two levels according to known literary sources. The first level is the individual financial valuation of the stocks of concrete stands with their mensurational characteristics, and the second level represents knowledge in this field for the lifelong development of forest stands and their total production in the form of value yield tables. Gross and net financial yield may be expressed, similarly like traditional yield tables or assortment yield tables, in dependence on the age and site index of stands.In published works the knowledge of the value production on both levels is available. Schroeder and Seemann (1987) reviewed the production of Douglas fir, spruce and pine in timber reserve, proportion of assortments, and gross and net yield. They based their own value calculations on standing resources of the studied tree species, their dimensional sorting, financial valuation of assortments and costs of logging operations. Bartelheimer (1991) calculated the gross and net yield of quality oak stands using the average prices of timber and costs of logging operations in Bavaria. Brandl (1986) calculated net yield for beech stands tended by various methods. Brandl (1989) dealt with the issue of net yield again, but from the whole forest operations, when he analyzed the results of economic activities of selected forest enterprises. Based on their economic records he derived such a minimum height of total mean increment in m 3 that the net yield of the whole forest production, including wood production, is still positive. Bergel (1986) described the procedure of derivation of value yield tables for Douglas fir with various tending intensity, yield level and rotation period. He used yield and assortment tables for their construction. He used the costs of logging and other silvicultural operations, including overhead costs, from the data of forest enterprises. Bachmann (1967) The results of research on the value production of the stands of poplar clones Robusta and I-214 carried out in Slovakia are presented. Models of value yield tables were constructed separately for each clone. The models simulate gross and net financial yield of wood production in dependence on the site index and age of stand. They were constructed on the basis of the models of assortment yield tables, timber prices according to assortments and the models of own costs of timber felling and processing. The clone I-214 produces a faster and higher proportion of thicker assortments of average and below-average quality, and therefore it has the higher value production at a younger age only. Robusta produces smaller diameter but higher quality assortments and has the higher value production only at an older age. The site index of the stand is the most important ...
ABSTRACT:The results of research on the production of raw timber assortments for the stands of poplar clones Robusta and I-214 in Slovakia are presented in this paper. Models of assortment yield tables were constructed, separately for each clone, in dependence on the yield class and stand age. The construction was based on the models of yield tables, stand assortment tables, models of external quality and damage to stems. Robusta clone produces by about 15-20% higher proportions of the highest quality assortments than I-214 clone. I-214 clone produces faster and higher proportions of average-and below-average quality assortments. their knowledge we may state that the methodologies of the construction of assortment tables accept mostly only dimensional sorting, where individual logs are divided according to mean diameter into diameter classes with the diameter 5 cm or 10 cm. Only occasionally are very simplified criteria used for the quality of stems or the crown parts of trees or possibly for their damage by rot. Dimensional sorting is justified in the above-mentioned cases by the fact that coniferous tree species such as spruce, fir and pine, which prevail in many countries, show very small differences in the quality of stems and prevailing assortments, frequently almost 90% of their volume, are saw logs. In this case it is sufficient to classify them into diameter classes.In Slovakia relatively great attention is paid also to quality sorting when for logs quality characteristics of wood are also considered, for example knots, decays, false heartwood, curvature, twisted growth of wood fibres, etc. Based on the original material of empirical sorting models of tree and stand assortment tables for 8 commercially important tree species were constructed, namely for spruce, fir, pine, oak and beech Nociar (1990, 1991) and for larch, hornbeam and birch Mecko et al. (1993). By connection of the above-mentioned models with the models of yield tables (Halaj et al. 1987;Halaj, Petráš 1998) assortment yield tables (Petráš et al. 1996) were constructed. In the last years models of the production of poplar clones Robusta and I-214 were completed. Mecko (2001, 2005) processed their volume production into yield tables, and the quality of production started with the construction of tree and stand assortment tables (Petráš, Mecko 2007;Petráš et al. 2008) and resulted in assortment yield tables.The aim of the paper is to present the methodology and the results of the construction of the models of assortment yield tables for poplar clones Robusta and I-214. MATeRiAlS ANd MeThodSAssortment yield tables show the structure of assortments, particularly their volume in m 3 or the proportion in % of the whole standing volume S(m 3 ,%) in dependence on the stand site index si and age t according to the relation:Assortment yield tables of poplar clones were constructed by the method of simulation from the models of yield tables, stand assortment tables, models of the quality and damage to stands. Models of yield tablesThey show the d...
ABSTRACT:The construction of a continuous mathematical model of frequency distributions of the diameters of trees of poplar clones Robusta and I-214 in dependence on tree diameter and mean diameter of stand is presented. Empirical material consists of diameter measurements on research plots from poplar regions in Slovakia. There were 90 plots for I-214 clone and 142 plots for Robusta clone. There were about 10-250 trees with mean diameter 2-70 cm on the research plots. The model was derived according to the three-parameter Weibull function. Its parameters were estimated by maximum likelihood method of the logarithm of the probability density function. Smoothed sample probability densities were processed in continuous mathematical models where the probability density of trees in stands is a function of their diameters and mean diameter of the stand. The method of regression smoothing of the parameters of Weibull function from sample sets in dependence on their mean diameter was used. In the whole range of mean diameters both clones have slightly left-skewed distribution with a relatively small variation range.
The paper presents models of decennial thinning percents of spruce in mountain locations. They were derived by regression fitting from empirical material with 108 measurements on 93 research plots. Models were derived for untended and partially tended stands. They were compared with the models of thinning percents of spruce at mountain locations from yield tables, induction thinning percents of spruce at lower locations and planned decennial thinnings according to forest management plan. Type of thinnings was analysed by means of thinning indexes and thinning intervals were proposed.
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