engleski

Diameter Increment of Silver Fir (Abies alba Mill.) during Timber Skidding in Gorski Kotar Region

Silver fir (Abies alba Mill.) is the most important commercial coniferous species in the Republic of Croatia. It is the main tree species of selection forests in Croatia that covers an area of 200, 000 ha. However, silver fir is the most endangered forest tree species due to the effect of different unfavorable biotic and abiotic factors. The outcome of these factors is a serious tree decline. Due to such a serious decline of silver fir trees, salvage cuttings and skidding of forest wood assortments are very frequent. Timber skidding causes damage to trees and forest soil affecting adversely the diameter increment and tree value, and resulting in tree decline. This paper presents the analyses of damage caused to trees by timber skidding. The aim of this research was to determine the correlation between the surface of tree damage and crown defoliation, as well as the relation between tree damage and diameter increment. On a permanent experimental plot of 2 ha covered with commercial silver fir forests in Gorski Kotar region (northwest Dinarides), perennial data were collected about crown defoliation, diameter increment and damage to silver fir trees caused by machinery. Damaged trees had significantly higher crown defoliation than undamaged trees. Crown defoliation significantly correlated with the damage surface and number of tree damages. The correlation was positive and low (r = 0.31). Damaged trees of all diameter classes had smaller diameter increment than undamaged trees. Damage surface, as well as number of damages had no significant correlation with tree diameter increment. The average tree damage surface was 607 cm2, and the average number of damages per tree was 1.5. The highest number of damaged trees was recorded in 3a defoliation class (60 – 80 % defoliation) and in diameter class above 50 cm. The largest damage surface was recorded in 3b defoliation class (80 - 99 %) and diameter class above 50 cm. According to damage surface classes, the highest number of trees was recorded in the first damage class (< 100 cm2). The highest number of damaged trees was recorded with dominant trees according to Kraft, and the largest damage surface was recorded on codominant trees.

Damaged trees; forest machinery; crown defoliation; diameter increment; silver fir; Abies alba Mill.

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