Evaluation of renewal volume methods of 3p and one hundred percent for hornbeam species. (Case study: District one of Shast-kolate Forestry Plan)

Accuracy in volume estimation of industrial as well as firewood of cut trees, which are the base of stumpage and toll collection calculation, is very important in forestry plans. This investigation aims to evaluate the 3P and traditional renewal methods of hornbeam trees in comparison to the actual volume of cut hornbeam trees in Bahram- Nia Forestry Plan. Therefore, 282 trees of hornbeam species were selected from official cut permission of the year 2011 of the mentioned forestry plan. At first the volume of selected trees were calculated using the traditional hundred percent volume renewal methods. Then the actual industrial wood, firewood and total volume of all hornbeam trees was calculated according to the 3P prescription. Volume estimation of hornbeam trees was done through 3P volume renewal method (in 5 replications). The results of these two methods were compared to the actual volume of cut trees. The results showed that there was a significant difference between the industrial wood, firewood and total volume in traditional method with the actual tree volume. Under estimation of industrial wood volume was due to Indiscrimination of decayed parts of trees, and over estimation firewood volume was due to calculating it according to difference of total tree volume (volume table) and industrial volume. Consequently, over estimation of total tree volume in traditional method was happen relatively. The difference of estimated volume between 3P method with the actual cut trees volume was 0.4 to 6.3 percent that is not statistically significant. Generally the total volume calculated by 3P method was less than (23.1 to 30 percent) the total volume calculated by traditional method. Regarding to the result of this study, the 3P method is suggested for volume renewal of cut trees in reclamation areas due to higher accuracy,to the traditional hundred percent method.