Environmental Effects of Skidder Traffic and Skidding Directions on Forest Soil Compaction and the Regeneration Establishment Condition in Choob-e- Farim Forests

 Forest soil compaction influenced by the use of skidders machineries, its power and weight, then causes changes on specific physical characteristics of soil. In most of the investigations, the negative effects of skidder traffic is reduction in growth of trees. The aim of this research was investigating the effects of number of skidder traffic in different skidding direction (uphill and downhill skidding) on soil compaction and forest seedlings establishment, through using rubber–tired skidder, the Timber jack 450c in compartments 9 and 11 series of the Dehmian exploitation corporation Choob-e-Farim company. The number of traffic at five levels (0, 1-5, 6-10, 11-15 and >15 passes) and two levels of skidding directions (uphill and downhill) were measured. After logging operations, sample plots with 9m2 size were recorded within the skidding trails. Bulk density, seedling density and root volume were measured on the disturbed surface and within the skidding trails. Results showed that the most bulk density increase was occurred during the first few passes of skidder (1-5 traffic). The increases in bulk density were considerable at the sampling depth of 20-30 cm. Uphill skidding soil compaction were higher (1/24 gr/cm3) than downhill skidding (1/19 gr/cm3). Uphill and downhill skidding directions did not affect the seedlings density. Traffics by more than 10 times at uphill and downhill skidding reduced the seedlings density and growth. The number of allowed traffics in uphill and downhill determined 7-8 and 11-12 times respectively.