Adaptive governance of Hyrcanian forests; mitigation of harvesting-induced disturbance impacts on forest soil

Adaptive governance of Hyrcanian forest soils requires a precise understanding of the consequences of harvesting on forest soil. This research studied the effects of logging operations on the soil physical and chemical properties at time intervals of 7, 10, 15, and 20 time since harvest (mid-term) after harvesting and under different traffic intensity levels (low, medium, high, and landing) in Hyrcanian forests (Kheyrud). Soil physical properties (bulk density, porosity, penetration resistance, moisture, and texture) and chemical properties (organic carbon, nitrogen, C/N, and pH) were analyzed using analysis of variance and multivariate analysis (PCA) in SPSS and SAS JMP software. The findings indicated that soil bulk density and penetration resistance in skid trails significantly increased compared to control areas, while soil porosity and moisture significantly decreased. Soil chemical elements, including organic carbon and nitrogen content, decreased, and the soil in skid trails became more acidic. PCA analysis confirmed that soil compaction and the indicators of bulk density and penetration resistance have a negative correlation with soil moisture, carbon, nitrogen, and acidity, and a positive correlation with the years since harvesting and higher traffic intensities. These factors are the most important causes of soil differences between degraded and undisturbed forest areas. Although a visible recovery trend was observed after two decades, the soil in skid trails in areas with higher traffic intensity has not returned to the condition of undisturbed forest areas. These results emphasize the necessity for integrated and ecosystem-based governance. Developing technical standards to reduce traffic, using low-pressure machinery, scheduling operations based on soil moisture conditions, and actively involving stakeholders in the sustainable management of forest areas are suitable strategies to mitigate these damages.