Thinning trials with a dedicated steep-terrain harvester

The study reports on two thinning trials carried out with the Valmet 500T dedicated steep-terrain harvester. The trials were conducted in California, on two different conifer stands: a second-growth natural forest dominated by white fir, and a young ponderosa pine plantation.The terrain was considerably steep, with an average slope gradient of 30% and peaks around 60%. The characteristics of both the stand and the terrain resembled those found on the European mountains, and especially on the Alps. The harvester proved capable of negotiating rough terrain, while remaining flexible enough to harvest different stand types. The plantation was much more difficult to harvest, due to the thick undergrowth and to the low branching of the trees. Productivity reached 25.1 m3/PMH in the natural stand and 11.3 m3/PMH in the young plantation. CTL technology is very interesting, because it offers the benefits of limited environmental impact, simpler logistics and increased operator comfort. Modern self-leveling carriers and efficient harvesting heads can take CTL technol- ogy to rough terrain and selection cuts, once considered beyond its range of applications.