Could timber winching operations be cleaner? An evaluation of two options in terms of residual stand damage, soil disturbance and operational efficiency

Forests provide multiple services, products and values and finding ways to preserve their multifunctionality is important. However, all of the currently used harvesting systems produce some degree of environmental damage, potentially affecting the provision services on the long term. Skidding operations are common in many regions of the world. Skidding may suppose three operational steps: winching, strip-road skidding and landing operations. By using cables for winching, wounds are commonly inflicted to the residual trees, while the mechanical traction of logs may cause damage to the residual trees and soil. This study was designed to check if the use of pans during winching deployed in thinning operations of coniferous forests may help lowering the environmental impact in terms of damage to residual trees and soil, while accounting for operational efficiency of such operations. Four treatments were considered and framed around the winching direction (uphill, downhill) and the use of protective devices (use, nonuse) and detailed data was collected on the residual stand damage, soil damage and time consumption. The main finding was that uphill winching by the use of a pan performed the best in terms of lowering the environmental damage. It shown the smallest wounds by their average area per tree, the lowest number of wounds per tree, the lowest rate of wounding per hectare, as well as one of the lowest rates of soil damage. By excluding delays, working with a pan did not cause additional time consumption, supporting acceptable rates of operational efficiency. Further experiments would be needed to validate and extend the results of this study, as the forests and their type of management are heterogeneous systems in terms of terrain configuration and slope, soil, species, stand density, removal intensity, operational timing and operational conditions.