Original scientific paper
Diameter Structure Models of Black Poplar Selected Clones in the Section Aigeiros (Duby) Obtained by the Weibull Distribution
Siniša Andrašev
orcid.org/0000-0001-7468-7819
; Institute of Lowland Forestry and Environment Novi Sad
Martin Bobinac
; University of Belgrade - Faculty of Forestry
Saša Orlović
; andrasev@uns.ac.rs
Abstract
The present study was performed in an experimental plantation with six 20-year-old black poplar clones in the Section Aigeiros(Duby). The diameter structure models were constructed using the Weibull probability density distribution with three parameters based on periodical measurements of diameters at breast height. The unidentified parameters were calculated by the so-called “hybrid system” (Knoebel, et al, 1986): location parameter (a) was calculated by percentile method, scale parameter (b) and shape parameter (c) were calculated by moments method. The applied method of estimating the location parameter (a) showed that in 90.6 % of the study sample, the parameter “a” ranged between 50 and 90 %, and in 52.4 % of the sample, “a” ranged from 80 to 90 % of the minimal diameter. With higher plantation ages, location parameter (a) and scale parameter (b) also increased with small oscillations, which was confirmed by the significance of the correlation coefficient of 0.71 and 0.73 respectively. This was shown by the shift of the curve of diameter structure model to the right, towards larger diameters, and in a wider range of diameters at breast height with a lower relative frequency of the modal degree. In the initial period, F-ratio of all three parameters of diameter structure model decreased and reached the minimal value in the eighth year, and the predominantly increasing trend started in the twelfth year, which points to the changes in diameter structure of the study clones depending on the age. The plantation growth elements (dg, G) and the Kolmogorov-Smirnov test, as well as the analysis of variance test and LSD test for the percentage of the number of trees with diameters at breast height above 40 cm, confirmed the grouping of diameter structure models of the study poplar clones in two groups. This makes it possible to define the differentiated management procedures with individual groups.
Keywords
black poplar; clones; diameter structure; Weibull distribution
Hrčak ID:
45101
URI
Publication date:
31.12.2009.
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