Determining the best stem form factor equation for populous deltoides in poplar plantations of Alborz Research Station, Karaj

Abstract

Populous deltoides has been proven to exceed other poplar clones in terms of growth and wood production per unit area. Thus, it is generally considered as one of the most crucial species for pulp and paper-oriented wood plantations in Iran. Here, a number of 40 trees was selected for developing true form factor (TFF) of P. deltoides. Prior to felling, the height and diameter of trees were measured. Following the felling, a set of variables including the length of tree (cm-accurate), the diameter in the 1/2 of total tree height (i.e. stump height + the length of felled tree), the diameter in 0.1, 0.3, 0.5, 0.7 and 0.9 of tree height and the top diameter of each 2 meter-high log (up to 5 cm stem diameter) were measured. Then, the Artificial, Hohenadl and Natural form factors were calculated, which were then compared with the TFF. The two-way ANOVA-based comparison of means amongst the form factors in different diameter classes revealed significant differences amongst the form factors of 15 and 25 cm with other diameter classes. All form factors showed insignificant differences except for the Artificial form factor which revealed to be significantly different than the TFF. Furthermore, the real tree volume across the study site can be derived by the calculated TFF value of 0.5028. For similar sites, this study concludes the alternative form factors (Hohenadl or Natural) to be able to be used for calculating standing volume being comparable to the real volume of P. deltiodes.

Keywords

• Populous deltoides
• true form factor
• Artificial form factor
• Hohenadl form factor
• natural form factor
• Karaj