Evaluation of 3P and 100% renewal volume methods (Case study: Parchiva forestry plan)

Renewal of wood volume by 3P method has been suggested to replace the 100% renewal method to reduce field work and costs. In this method and following selection of sample trees from marked trees, the volume of industrial trunks and firewood in trees are field-measured. In order to evaluate and compare the full and 3P renewal methods in the Parchiva forestry plan in Mazandaran province, 1184 maple, ironwood, alder, beech and hornbeam were selected. The trees were first measured by 100% renewal method, followed by separate allocation of actual volume to industrial, cordwood and total volumes according to the procedure of 3P method. Estimation of tree volume was done by 3P method in 10 replications. The results of paired samples t-test showed a significant difference between 100% and 3P renewal methods for maple, ironwood and alder, while no significant difference was observed for beech and hornbeam (p < 0.05). An independent samples t-test also showed that volume estimation by 3P method did not reveal any significant difference on maximum and minimum error levels. The results of this study suggested the 3P method as a cost- and time-effective alternative to the full renewal method.