DIGITALNA ARHIVA ŠUMARSKOG LISTA
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|ŠUMARSKI LIST 3-4/2012 str. 53 <-- 53 --> PDF|
For the determination of calorific values of wood of the young plants the specimens were increment cores (Pressler’s increment borer) taken at breast height (1.30 m) of sample trees (Pollanschutz 1963). For the older plants the specimens were 5 cm thick disks taken at breast height. The specimens were dried at room temperature until moisture content was 8–10 %, and after that the samples were ground into wood flour suitable for pellet pressing. The calorific value was determined for ground air-dried samples. Pellets were made by a special device producing pellets ranging from 0.60 g to 0.85 g. Samples were combusted in C200 IKA Werke calorimeter. There were three replications for each sample.
The heat which could be produced by full combustion of the aboveground biomass (without leaves) per hectare was calculated based on the calorific value of wood of individual clones.
For the determination of moisture content, wood samples were oven dried at 104 °C to a constant weight. All analyses were done in duplicate and the results were expressed on a dry weight basis.
Wood density was determined on the basis of oven-dry weight per green volume of an individual wood specimen. Green volumes were obtained by soaking specimens in water until constant volume was achieved. Excess moisture was removed from the surface of the sample, and each sample’s water displacement (volume) was measured. The sample was then oven-dried to constant weight at 104 °C and weighed to determine the dry weight.
The data were subjected to various statistical analyses including: means, calculation of parameter coefficient of variation, analysis of variance (ANOVA) and LSD test.
Results and discussion
Growth elements – elementi rasta
Growth elements, and values of wood densities for examined poplar clones were determined within first and second years (Table 2 and 2a), and after seventh growing season (Tables 3, 4).
After first year of shoot growth, average height varied between 2.0 m and 2.8 m, and average diameter was from 1.2 cm to 2.5 cm. Volume, i.e. volume increment, calculated based on the average value of plant diameters and heights ranged from 4.32 m3ha–1 (cl. ‘Pannonia’) to 14.87 m3ha–1 (cl. ‘B81’). Average wood volume of all clones amounted to 9.65 m3ha–1.
After the second year (cumulative, for two-year old plant), average height ranged between 6.1 m and 7.7 m, and average diameter varied between 3.5 cm and 4.5 cm. Coefficients of variation (C.V.) for diameters and heights of trees after first and second year were small. Results of ANOVA showed statistically high significant differences between clones (F = 19.91*** and F = 43.21***). Biomass volume ranged from 24.51 m3ha–1 (cl. ‘182/81’) to 46.86 m3ha–1 (cl. ‘B229’). Average biomass volume of all clones was 36.65 m3ha–1.
Results of ANOVA for the Experimental plot 2 (Table 3) showed there are not significant differences between replications, but inter – clone differences were significant for diameters and heights (F = 42.72*** and F = 5.82***).
After seventh year of growth in the Experimental plot 2, average diameter varied between 19.5 cm and 24.3 cm, and average height was from 18.7 m to 20.5 m. This agrees with the