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Open access

Rudolf Petráš, Julian Mecko and Ladislav Kulla

Abstract

Tree maturity of the four main tree species that are most frequent in the uneven-aged forests of the Western Carpathians was analysed. The maturity was determined on the base of the economic value production in relation to tree diameter. We derived mean timber values of spruce, fir, pine, and beech trees (€ m−3) depending on their diameters, quality and stem damage, and in the case of beech also depending on tree age. The assortment structure was calculated using the models of tree assortment tables that account for the stated tree parameters. The assortment prices were taken from the price list of logs in assortment and diameter classes of the Forests of the Slovak Republic, state enterprise, for the year 2016. Trees are mature when their mean timber monetary value is at maximum. Results show, that the highest mean value production of the majority of beech trees of average and above-average stem quality is 70 - 80 € m−3 for trees with diameters between 45 and 55 cm. Monetary values of spruce and fir trees with diameters above 60 to 90 cm are 80 - 95 € m−3, while the monetary values of pine trees with the same diameters are approximately 70 - 115 € m−3. The value production of trees is reduced if the stems are of worse quality or damaged, but in the case of beech it also decreases with greater diameter or tree age.

Open access

Rudolf Petráš, Julian Mecko and Viera Petrášová

Abstract

Calorific value production from the above-ground biomass of stands was derived from its volume production. The mathematical models of growth tables of I-214 and Robusta poplar clones, biomass density values and calorific values of biomass dry matter were used for its calculation. At the stands aged 35 years and site indices of 20, 30 and 40, the calorific value has approximately 2.700, 6.000 and 9.300 GJ.ha-1 respectively. The I-214 clone has higher production than Robusta in the first half of its growth, albeit with minimum differences. The annual increments of calorific value culminate about the age of 9-13 years with values of 450-115 GJ.ha-1. Mean annual production of both clones culminates at the age of 17-26 years with values of 320-80 GJ.ha-1. Lowland forest locations with high level of ground water in Slovakia with the total area of 25.600 ha are most suitable for poplars production. On this area, we can assume the mean annual production of 3.566 TJ of gross calorific value obtained from above-ground biomass in the future. From that, about 64% is in wood, 14% in bark and 22% in small-wood. Up to 85% of this production potential is situated in the area of The Danube Lowland and the rest is mainly in southern areas of the Central and Eastern Slovakia.

Open access

Rudolf Petráš, Julian Mecko and Viera Petrášová

Abstract

Poplar clones reach a big advantage over other forest tree species in the production of large amounts of above-ground biomass in a relatively short time. To increase the efficiency of production during their short life cycle, it is necessary to optimize age of their felling maturity. It should be carried out in the stands age when its average production is highest. Mathematical models of yield tables were used to derive this production. Above-ground biomass production was expressed in natural units, volume (m3 ha−1) and the capacity of calorific value (GJ ha−1), but also in financial yield (€ ha−1) from the sale of timber assortments including energy chips from smallwood. In terms of financial yield, Robusta stands are mature between 23 and 35 years and I-214 stands between 18 and 32 years. Main financial yield per year, on average 200–1900 € ha−1, is expected from the production of assortments designed for classic industrial processing. Its increase by 50 to 100 € ha−1 is expected to be achieved by supplemental smallwood processing to energy chips. In terms of volume production and capacity of combustion heat, stands are mature about 5–7 years earlier.

Open access

Rudolf Petráš, Julián Mecko, Michal Bošeľa and Vladimír Šebeň

Abstract

Stem quality and damage was evaluated in mixed spruce-fir-beech stands. Moreover, an assortments structure was determined with their financial value. Results were compared with pure spruce (Picea abies [L.] Karst.), fir (Abies alba Mill.) and beech (Fagus sylvatica L.) stands. Repeated measurements on 31 long-term research plots, stand assortment models, assortment yield models and value yield models were used. Stem quality of fir and spruce was only slightly lower in mixed stands compared to pure stands but beech stem quality was considerably worse in mixed stands. Fir and spruce had slightly lower proportions of better IIIA quality logs and higher proportions of IIIB quality in mixed stands. Beech had worse assortment structure than spruce and fir, in general. Pure beech stands had higher proportions of better I–IIIA quality assortments than mixed stands by 1–7%. Fir and spruce average value production (€ m−3) culminated at about 56 and 62 cm mean diameters. Almost the same value production was found in pure stands. In these stands it culminated at the mean diameter of 58 and 60 cm. Beech produced substantially less value on the same sites. In mixed stands, its value production culminated at the mean diameter of 40 cm. In pure stands, it culminated at the mean diameter of 36 cm. Although the production was found to be similar in both mixed and pure forests, higher damage intensity and less stem quality in mixed forests suggest that the pure forests can be more profitable.

Open access

Rudolf Petráš, Michal Bošeľa, Julian Mecko, Julius Oszlányi and Ionel Popa

Abstract

Height-diameter models define the general relationship between the tree height and diameter at each growth stage of the forest stand. This paper presents generalized height-diameter models for mixed-species forest stands consisting of Norway spruce (Picea abies Karst.), Silver fir (Abies alba L.), and European beech (Fagus sylvatica L.) from Slovakia. The models were derived using two growth functions from the exponential family: the two-parameter Michailoff and three-parameter Korf functions. Generalized height-diameter functions must normally be constrained to pass through the mean stand diameter and height, and then the final growth model has only one or two parameters to be estimated. These “free” parameters are then expressed over the quadratic mean diameter, height and stand age and the final mathematical form of the model is obtained. The study material included 50 long-term experimental plots located in the Western Carpathians. The plots were established 40-50 years ago and have been repeatedly measured at 5 to 10-year intervals. The dataset includes 7,950 height measurements of spruce, 21,661 of fir and 5,794 of beech. As many as 9 regression models were derived for each species. Although the “goodness of fit” of all models showed that they were generally well suited for the data, the best results were obtained for silver fir. The coefficient of determination ranged from 0.946 to 0.948, RMSE (m) was in the interval 1.94-1.97 and the bias (m) was -0.031 to 0.063. Although slightly imprecise parameter estimation was established for spruce, the estimations of the regression parameters obtained for beech were quite less precise. The coefficient of determination for beech was 0.854-0.860, RMSE (m) 2.67-2.72, and the bias (m) ranged from -0.144 to -0.056. The majority of models using Korf’s formula produced slightly better estimations than Michailoff’s, and it proved immaterial which estimated parameter was fixed and which parameters were free

Open access

Tomáš Klouček, Igor Štefančík, Rudolf Petráš, Julian Mecko and Martin Slávik

Abstract

The models of height curves were derived from repeated measurements at six permanent research plots in the experimental object of Komárnik situated in the Eastern Carpathians. During more than 50 years of investigation, the heights of 1,346 beech and 1,208 fir trees were measured. Tree heights had a great variability, but the stage-shift of height curves was not confirmed. The non-linear regression models of height curves for beech and fir were derived, where tree height is a function of tree diameter and model height for a selected diameter class. They are based on the Korf growth curve with three parameters. The models explained 90% and 94% of beech and fir height variability, respectively. The models confirmed the actual knowledge that fir had higher tree height increment than beech especially for trees with greater diameters. The comparison of our models to those developed by other authors showed that the shape of height curves slightly differed. Beech curve was characterised by greater, while fir curve by lesser curvature in comparison with other published models. Our models have only local validity due to the limited scope of experimental data. They can be applied under the local conditions in order to perform valuation and simulation of growing stock development and increments of uneven-aged and multistoried fir-beech stands.