The medium-term effects of forest operations on a mixed broadleaf forest: Changes in soil properties and loss of nutrients

This study took place in a mixed deciduous forest located in Northern Iran to investigate the effects of two types of silvicultural methods, specifically the single-selection method and the group-selection method. The study also included the observation of skid trails in terms of runoff, sediment yield, and the loss of NO3-N and PO4-P. The process of recovery was studied by the assessment of these characteristics after the completion of forest operations for a period of 3 years. Although there is a considerable amount of literature on the topic of soil erosion caused by forest harvesting, there is little information regarding the medium-term effects of different sizes of gaps in the forest canopy. The attempt to gather data was done by designating hillslope plots on the soil directly affected by machinery passage on skid trails, as well as on the felling gaps in correlation with the two types of silvicultural methods. Plots were also marked on an unharvested area as a control. The results confirmed the suitability of retention forestry within the framework of sustainable forest management. A majority of the data gathered showed no difference between the single selection and the control area. What is more, the values obtained from the felling gaps correlated to the group selection resulted to be the same as the control values 2 years after harvesting. However, the disturbance caused by machinery passage on skid trails showed a significantly higher level of impact, and the recovery time needed was at least 3 years.