Using 137Cs tracer to assess the effects of silvicultural systems on soil redistribution in Hyrcanian forest, Mazandaran—Iran

The middle zone of the Hyrcanian forest located in the Mazandaran—Iran has experienced several silvicultural systems in which wood harvesting using clear-cutting, shelterwood, single-selection methods, and reforestation implemented under even- or uneven-aged stands for the past four decades. Studies on their implications led us to apply innovatively nuclear techniques to estimate their impacts on soil redistribution. The reasonability of the 137 Cs inventory (4335 Bq m −2 ) and soil organic carbon (SOC) stock (220 t ha −1 ) in the representative reference site was approved. However, results imply losing ≈ 110 tones of SOC per hectare through silvicultural systems since their initiation. In addition to SOC, the annual soil erosion rate due to cultivated uneven-aged trees was 28.16 tonnes per hectare (1.5 mm yr −1 ); in contrast, the soil erosion (per hectare) through the cultivation of even-aged trees has been annually 14.5 tones (0.095 mm yr −1 ). The ability of nuclear techniques to reveal a higher soil-conserving efficiency (≈ 50%) of even-aged stands compared to uneven-aged trees and up to 15% restoration of SOC stock was the desired achievement. Practical strategies and approaches for silvicultural systems to restore degraded forest watersheds were tangible outcomes of the research. Forest management plans will be more effective for soil conservation using the introduced preferential cultivation methods. Scholars should consider the FRN's properties and the IAEA standards for such studies.