Assessment of soil recovery and establishment of natural regeneration 20 years after stopping from ground-based skidding

Ground-based skidding operations are known as an important source of damages to the residual stands and surface soil of forests. This research aims at studying the soil compaction and establishment of natural regeneration in an abandoned skid trail 20-year after cessation of timber harvest operations. For this purpose, an abandoned skid trail about 1 Km in length was chosen by field inspection at Neka-Zalemrud forest catchments. Before sampling, the skid trail was divided into three traffic intensities (low, medium and high) based on distance to log-landing. Two slope categories were then delineated for each traffic intensity. Treatments include three traffic intensities and two slope classes with three replicates for each category. Three sample plots (4×10 m) out of five ones were randomly selected for taking soil samples. The effect of soil compaction on all established regenerations was studied in same plots.  Results showed that with increasing the traffic intensity and slope gradients, soil bulk density did not decrease compared to controlled areas. Soil bulk density values remained by about 6.12, 41.38 and 40.38 and 37.75, 17.34, and 45.91% for slope class 0-20% and over 20% within three traffic intensity including low, medium and high, respectively. Furthermore, results confirmed that the most tolerant and intolerant species to the compaction were beech and maple and alder in high traffic intensity, 20- year since stopping timber operations, respectively. To minimize the negative impacts of skidding operations on forest soils, permanent skid trail is required and ground-based skidding operations should be limited to areas where slope gradients do not exceed 20%.