Impact of wood harvesting systems on round wood quality

The increase in the use of mechanised harvesting systems has led to log damage, including butt pull, log splitting during handling, and the bucking and crushing of the log. Damage to a harvested log can occur during the felling, delimbing, bucking, skidding or forwarding, piling, loading, and hauling functions of wood harvesting. The world's best harvesting operations using modern CTL machinery – many of them in Nordic countries – are currently losing 4 – 5% of wood value at harvest. However, wood harvesting operations in many countries, such as Russia, using a number of different harvesting systems, such as the motor-manual full-tree system (MM FT), fully mechanised FT system (FM FT), MM CTL system, FM CTL system, and MM TL system, have shown losses of 11–18% of the wood value at harvest. Certainly, the influence of wood quality on the value of industrial roundwood (IRW) cannot be ignored when comparing different technologies. This is determined by evaluating it in accordance with the quality specifications in the customer contracts as well as other quality requirements. To remain competitive, logging companies should also minimise wood loss at the time of harvest by using more advanced harvesting technologies. One of the major opportunities of this study was to identify damage to IRW arising from applied harvesting systems in Russia in order to minimise this damage loss. The following volume losses of IRW (in terms of the reject rate as a percentage of total IRW on average per year) were found by the harvesting system: 1.8% in MM CTL; 2.3% in FT CTL; 5.0% in MM TL; 4.2% in MM FT; and 3.3% in FM FT. The total average volume loss of IRW in the studied companies was 3.6% or around 67,000 m3 of IRW per year. The following value losses of IRW (in terms of value loss per unit volume of IRW) were found by the harvesting system: 0.51 €/m3 in MM CTL; 0.65 €/m3 in FT C TL; 1.38 €/m3 in MM TL; 1.04 €/m3 in MM FT; and 0.86 €/m3 in FM FT. The total average value loss of IRW in the studied companies was 0.98 per €/m3 of IRW or around 1.8 million €/year. The presented analysis indicates that CTL harvesting can ensure the highest quality of harvested wood (reject rate below 3% of observed logs) in all studied companies, with different species compositions. The FT harvesting systems demonstrated acceptable IRW quality (reject rate about 3–5%). The quality of wood in TL harvesting was low (reject rate over 6%), particularly in summer (reject rate up to 10%). Certainly, an improvement in harvesting operations is needed for a reduction in IRW losses – even in the same harvest system. Loggers (operators and lumberjacks) need to pay more attention to value rather than volume alone, which could be accomplished by the development of a payment system and harvesting instructions for utilising the forest resources better by not damaging valuable logs. The reject rate is higher for the MM CTL system in winter and for the MM TL and MM FT systems in summer, indicating that seasonality should be taken into account. The potential reduction in the rejection rate was roughly estimated from the best practices in the studied logging companies and common practices. If all the discovered shortcomings typical of FM CTL and FM FT harvesting were eliminated, it should be possible to decrease the reject rates by approximately 20% and 25%, respectively. It should be noted that the bucking optimisation of the FM CTL harvesting system allows for an increase in the amount of received IRW assortments. Improvements made to the MM CTL system would enable the reject rate to be reduced by approximately 15%. In the MM TL and MM FT systems, the potential reductions in the amount of damaged logs could reach 20% and 15%, respectively. IRW damage in terms of value loss per unit of volume in the studied companies may not seem important. This is especially true when looking at the small differences between the FM CTL and MM CTL systems. However, the switch from the traditional MM T