Effect of the conversion factor *212 on the estimation of log volume in the forest industry of Durango, Mexico

Resumen

Objective: to analyze Doyle and Smalian cubing methods, comparing their behavior in the application of conversion factors in the forest industry in Durango, Mexico.

Design/ Methodology/ Approach: A total of 38 731 logs were measured in different log yards and cubed using the Doyle (board ft) and Smalian (m^{3 )} methods. The volume calculated using the Smalian method was multiplied by the operational standard *212, a conversion factor which is used to obtain volume in tables (board feet) from roundwood. The volume estimate by diameter category and log length was analyzed using the Kruskall-Wallis test (p ≤ 0.05) to test differences between the Smalian×212 and Doyle cubing methods .

Results: eighty percent of the surveyed forestry companies use the Smalian method (m³) to calculate the volume of roundwood in their log yards, then, use the factor *212 to convert cubic meters to board feet. The volume was found to be significantly greater with the Smalian equation; however, for diameters of 65 cm and larger, the estimated volume is greater with the Doyle equation. For logs with diameters 37–55 cm, or lengths 2.44–6.71 m, estimation with the conversion factor is closer to the actual metric volume.

Limitations/ Implications of the study: due to internal policies, 20% of the companies interviewed did not respond. However, because of the significant nature of the differences, this study confirms underestimation or overestimation of log volume when using standardized estimation methods based on economic utility. Furthermore, the accuracy of log volume estimates is relevant in terms of sustainability.

Findings/ Conclusions: to use empirical factors is now obsolete and should not be mixed with different measurement systems, as their theoretical framework is different. Cubing methods should not be mixed, since the conversion factor *212 currently used with Smalian equation renders estimations not equivalent to actual cubic measures under the official International Standard of Units in terms of roundwood cubing.