Effects of rubber-tired skidder and farm tractor on physical properties of soil in plantation areas in the north of Iran.

Physical properties of soil can be affected by machines that are used for skidding which have the potential to impact soil sustainability and forest productivity. The present study evaluated the effect of timber skidding by a rubber-tired skidder and farm tractor on the soil physical properties. The study site was located in Hafdaghanan plantation region in the north of Iran. Two treatments that consisted of skidding by HSM 904 skidder and ITM285 farm tractor equipped with trailer were applied. The trails were included in three traffic levels: primary, secondary and tertiary. Treatment effects were tested using analysis of variance (ANOVA) with skidding machine types and traffic levels. Results indicated that machine type and traffic intensity are the effective factors on soil physical properties. The results showed that with an increase of traffic frequency, bulk density increased but total porosity and soil water content decreased. The results of the study provide clear evidence that farm tractor is a more environmentally friendly machine than rubber-tired skidder in the plantation area.