Damage evaluation of the remaining standing trees in a timber yarding operation: case study
1996
Hernandez-Diaz, J.C. | Delgado-Pacheco, M.
Equipment productivity and damage to residual trees were estimated at a timber yarding operation with "motogrua" (yarder), as a reference to compare proposals intended to improve the yarding methods most commonly used in Mexico. The performance of three motogruas was evaluated with regard to yarding and loading, and just loading of sawlogs and electrical transmission line poles. The average size of the pieces wa 0.778 m3r (round timber) and mostly just one piece was yarded per turn, since only the mainline is pulled out to directly tie and yard the logs. In this report reference is made to the analysis of damage to the residual trees caused by the yarding operation. Data were gathered at seven sites after the yarding operation had taken place, to observe the width, length and layout of the yarding roads, as well as the damage suffered by the residual trees standing inside those roads. The following results were found: Given a cut volume of 65 m3rwt/ha (whole tree), equivalent to 41 m3r/ha, timber yarding with motogrua resulted in drastic damage to 1.845 m3r/ha of residual commercial size trees, equivalent to 37 percent of the volume of this type that remained standing in the yarding roads. Also, more than 68 percent of the non-commercial size trees (with less than 10 cm of normal diameter), standing inside the yarding roads suffered severe damage. A recommendation is made to define and clear in advance the yarding roads to be used, not only making a more sound yarding operation, but also seeking to reduce the number of hang-ups and therefore the time and effort needed from the equipment and people. This would lead to improved efficiency and reduced production costs.
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