Preparation of volume table of industrial species of beech based on data obtained from 3P sampling method

Determining and estimating the volume of trees in the forest is one of the important issues in forest management. One way to reduce the cost and increase the speed of data collection is to use volume tables to estimate the volume inventory of a forest. In this research, the preparation of volume tariffs and their accuracy were investigated.  

For this purpose, 899 data obtained from 3P sampling and beech re-sizing in Kheyrud forest of Nowshahr were used to prepare the tariff. R software was used for statistical analysis. Using one variable linear regression, the best relationship for determining the volume based on diameter equal to the chest was fitted. To select the best regression relationship, statistical criteria of data distribution charts, box charts, residual charts, analysis of variance were used and to validate models VIF, AIC, and BIC criteria were used. The selected regression relation was used to prepare the tariff.

The resulting volume tables were obtained in the same range from the data used to obtain the regression relation. Then the prepared tables and the available tables were compared by paired t-test. According to the results of the statistical test, at the 95% level, there is no significant difference between the measured volume and the corresponding predicted volume.  

According to the results of this study, 3P sampling method is recommended for re-volume of beech trees due to cost reduction, time acceleration and appropriate accuracy compared to the traditional 100% method.