Determination of the absolute harvesting age of Paulownia even-aged stands in Dr. Bahramnia's Forest Management Project

To determine the best absolute harvesting age (quantitative purpose) and maximum production per area of a 18- year-old stands of Paulownia fortunei plantation at Dr. Bahramnia Forest Management project, Three spacing treatments including 3x6, 5x8 and 6x10 m. were examined. Five typic trees with normal diameter class distribution were chosen from each spacing treatment, randomly. The selected trees were fell down and sample discs were made from the stems at 0.4, 1.3 m. and then at 2 m. intervals between 1.3 m. and top height. Diameter and height growth were measured, based on stem analysis method. Stand volume, mean and current annual volume growth at different age stages were calculated, based on calculating fom factor at various age stages. Overall, the absolute harvesting age (forester’s criteria) was determined. The results showed that the absolute harvesting ages at 3x6, 5x8 and 6x10 m. spacing treatments were 11, 11 and 13 years, respectively. In addition, the trees at 5x8 m. spacing treatment had the greatest individual mean annual volume growth, but in respect to trees density per hectar, the trees at 3x6 m. spacing treatment achieved the heighest mean annual wood production per hectar in comparison to the other spacing treatments, which was 525/98 m3/ha. Therefore, it could be concluded that if the aim of Paulownia plantation is quantitative wood production, the spacing of 3x6 m. will be the best, but if the purpose is agroforestry, the spacing of 6x10 m. will be better than the spacing of 5x8 m.