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ŠUMARSKI LIST 11-12/2020 str. 24     <-- 24 -->        PDF

with no domination were classified as mixed forests. The percentages of ground cover and canopy cover were measured using a sighting tube with a diameter of 5 cm and cross threads taped across one end of the tube. The presence of vegetation at the intersection was recorded as a positive reading. In each plot, 20 measurements were conducted along four small transects inside the plot (to the N, E, S and W). The shrub coverage was determined using detailed photographs taken from the centre of the plot in four directions. It was then expressed as a percentage of plot covered by shrubs and pooled in four categories: 0-25%, 25-50%, 50-75%, 75-100%. The number and diameter of dead trees was recorded on each plot.
Shapiro-Wilks W test showed that variables were not normally distributed. Therefore, non- parametric correlation tests were used. PCA analysis with 28 independent structural and floristic habitat variables was conducted. They include relative number of trees and relative basal area for dominant tree species, total number of trees and tree species per point, total number and ratio of “small” and “large” trees, stand age, canopy and ground cover and percentage of shrubs (Table 1). Factor scores greater than [0.7] were considered to be significant.
Spearman rank correlation between primary components and number and abundance of secondary hole-nesting bird species was conducted. Shannon-Weiner index was used to calculate the diversity of communities. Statistical analyses were performed using Past v.3.14. and STATISTICA v.8.0. software.