Effects of road construction on soil degradation and nutrient transport in Caspian Hyrcanian mixed forests

•Effects of forest roads on soil degradation have been explained.•Effects of road erosion on soil characteristics have been considered.•Investigated the effective distance from roads that effects on soil degradation•Effects of different road ages on soil degradation have been investigated in this study.

Forest roads are the most essential projects in forest management. The aim of the present study was to investigate the effects of topographic factors on nutrient transport and degradation areas resulting from forest road construction in the Research and Educational Forest of Tarbiat Modares University in Iran. In this study erosion features around the forest road with a distance of 50 m from the road were documented using a Global Position System (GPS). Work units were determined by using slope, aspect and elevation maps. In addition, physical and chemical soil properties were determined in 19 work units for erosion regions, non-erosion regions and control regions. Results of correlation analysis between regional erosion features with distance to the road and number of erosion features show a significant correlation at the 99 percent level of confidence interval. Furthermore, there is a significant correlation between areal erosion features and elevation classes, slope, road age classes and aspect at the 99, 95, 95 and 95 percent significant level, respectively. Results of analysis of variance (ANOVA) show that areal erosion features at different elevation classes, slope, aspects and road age classes have a significant difference at the five, five, one and five percent level, respectively. Results of ANOVA for physical and chemical soil properties on erosion areas, non-erosion areas and control areas conveyed significant difference in pH, soil organic matter, silt, clay, nitrogen and phosphorus. These findings demonstrate the connectivity of soil properties when they are impacted by human activities.