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Seasonal Impacts on Bark Loss for Douglas-fir and Ponderosa Pine Harvested on the Pacific Northwest Coast of the USA

Abstract Although only a few harvesting systems today intentionally remove bark prior to transporting logs to the mill, little is known about how much bark is lost during harvesting operations at different times of the year. Depending on where you are located in the forest to mill supply chain, the presence or absence of bark can be seen as a cost or a benefit. Understanding the magnitude of bark loss and the factors that affect it should lead to minimization of the costs and maximization of the benefits. Quantification of seasonal bark loss (expressed as a percentage of the surface area of the stem) for two commercial tree species was conducted monthly over a 10-month period. All assessments were carried out on Douglas-fir and ponderosa pine harvesting operations that were using mechanized processor heads with chains over rubber feed wheels. Over 400 stems were assessed. There was a substantial (up to five times) increase in bark loss during late spring and early summer compared with the winter season. We were also able to show that the amount of bark loss is species dependent, with Douglas-fir incurring more than twice the bark loss than found for ponderosa pine. It is possible that the distribution of bark loss along the stem is also species dependent; we found greater bark loss towards the top of the stem in ponderosa pine than towards the bottom of the stem, but no such trend for Douglas-fir.