Evaluation of long-term soil compaction impacts on the restoration of soil physical properties and regeneration in skid trails of the Shirgah forests

In recent years, the study of recovery processes of skid trails has gained momentum. Therefore, the aim of the present study is to evaluate the long-term effects of soil compaction on the recovery of soil physical properties and regeneration in skid trails. In this research, four skid trails with age classes of 5, 15, 25 and 35 years were selected based on the last year when logging was done on the skids. Each age class was randomly selected with 3 repetitions, and three traffic intensities—low, medium, and heavy—were identified on each skid trail. In total, 72 soil samples were collected from skid trails and 24 soil samples from a control area. To evaluate regeneration on the skid trails, a plot of 40 m² was randomly established in each traffic intensity. Within each plot, regeneration was assessed by determining the species type and counting the number of seedlings of each species. Across all skid trails, bulk density, penetration resistance, and micro-porosity increased, while total porosity, macro-porosity, and soil moisture decreased with increasing traffic intensity from low to high. The natural regeneration of all species differed significantly between the skid trails and the natural forest. The findings confirm that the recovery rate is a long process and more time than 35 years is required for the full recovery of physical characteristics. Since the Hyrcanian forests are biodiversity hotspots, forest managers should pay special attention to mechanized wood harvesting operations in these areas, as the recovery of compacted soils requires decades.