The Impact of Animal Logging on Residual Trees in Mixed Fir and Spruce Stands

Background and Purpose: Logging is an example of the strongest human influence on forest environment because it causes damages to the forest soil and residual trees. The damages that occur during logging are more frequent in the skidding phase compared to the felling and processing phase. Material and Methods: The research was conducted in mixed stands of fir and spruce in the area of eastern Bosnia and Herzegovina. Felling was conducted by chainsaw and extraction by animals, i.e. by two oxen. The following data were collected: tree species, diameter at breast height, pre-bunching zone (0-30 m or 30-60 m), presence of damages, presence of old damages, number of damages, type of damage, damage position and the size of damage. Results: Damages were recorded on 3.32% of residual trees. The average number of damages per damaged tree was 1.08. The same percentage share of damages was recorded on butt end and root collar (38.46%), while damages on root have a share of 23.08%. Stem damages were not recorded. The most common type of damage was debarked tree (61.54%), then squashed bark (23.08%) and debarked and damaged tree (15.38%). It was recorded that the size of damages varied between 60 and 570 cm2. The average size of damage was 222.54 cm2. Statistical analysis using χ2 test showed significant difference in the proportion of damaged trees among different pre-bunching methods, and did not show significant difference in the proportion of damaged trees between different pre-bunching zones. Conclusions: It can be assumed that oxen logging causes insignificant damages to residual trees. The results of research will be used as a basis for future studies of residual trees’ damaging during wood skidding.