The Effects of Organic Mulches on Water Erosion Control for Skid Trails in the Hyrcanian Mixed Forests

Ground-based skidding can lead to severe soil disturbance by increasing surface water flow and soil erosion. Organic mulches have been shown to be effective in contrasting this type of soil disturbance, although the cost/benefit aspect has yet to be studied. This study, by installing runoff sample plots, aims to elucidate the effects of litter (LM) and sawdust (SM) mulches with three application rates (litter: 7.6 Mg ha-1 LM7.6, 14.6 Mg ha-1 LM14.6, 22.5 Mg ha-1 LM22.5; sawdust: 5.3 Mg ha-1 SM5.3, 11.4 Mg ha-1 SM11.4, 16.7 Mg ha-1 SM16.7) on runoff, soil, and nutrient loss (nitrate and phosphate) in skid trails established in the Hyrcanian forest. The results were also compared to the undisturbed area (UND) and to an untreated skid trail (UNT). The results showed that both litter and sawdust mulch significantly decreased runoff, soil loss, and nitrate and phosphate loss. The values of runoff, runoff coefficient, soil loss, NO3, and PO4 were at the highest level in the untreated skid trails (UNTs). The runoff, runoff coefficient, soil loss, NO3, and PO4 gradually decreased as the application rate of both the litter (LM) and sawdust (SM) mulches increased. According to the results, it is possible to conclude that the mulch application rates of 7.6-14.6 Mg ha-1 and 5.3-11.4 Mg ha-1 for litter and sawdust mulch, respectively, can be applied to maintain soil and water conservation after logging operations on skid trails. The obtained findings can help to shape specific best-management practices for the implementation of sustainable forest operations in the context of the study area, by indicating suitable mulch types and application rates to decrease the negative effects of erosion.