1. Environmental impacts of boom-corridor and selectively thinned small-diameter-tree forestsTeresa de la Fuente, Dan Bergström, Raul Fernandez-Lacruz, Teppo Hujala, Nike Krajnc, Ruben Laina, Tomas Nordfjell, Matevž Triplat, Eduardo Tolosana, 2022, original scientific article Abstract: European forest stands of small-diameter trees can provide industries with biomass as an alternative to fossil use. Small-tree harvesting is costly using conventional methods but using accumulating felling heads (AFH) in combination with a novel boom-corridor thinning (BCT) technique can increase harvester productivity and supply cost efficiency. This method has great potential to reduce costs, but its environmental impact compared with selective thinning (ST) needs to be determined. The objectives of this study were therefore to quantify and compare tree and soil damage as well as air, water and soil emissions for both BCT and ST in various European small-diameter-tree forests. Trials were performed in 84 study units (42 replications per thinning technique) across four countries. Damaged trees (with a diameter at breast height ≥ 7 cm) were measured after thinning and after forwarding. Harvesting emissions were calculated from a life cycle assessment. The percentage of remaining trees that had been damaged by the harvesting processes was 13% and 19% for BCT and ST, respectively, and the difference was significant. BCT exhibited the lowest emissions in all environmental impact categories considered, in all countries. Greenhouse gas emissions were on average 17% lower for BCT. BCT in small-diameter-tree stands therefore reduces the environmental impact of thinning operations compared with conventional methods, and results in less damage to the remaining trees. Keywords: first thinning, harvesting damages, GHG emissions, forest biomass, forest operations Published in DiRROS: 17.05.2022; Views: 845; Downloads: 488
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2. Effects of boom-corridor thinning on harvester productivity and residual stand structureDan Bergström, Raul Fernandez-Lacruz, Teresa de la Fuente, Christian Höök, Nike Krajnc, Jukka Malinen, Yrjö Nuutinen, Matevž Triplat, Tomas Nordfjell, 2022, original scientific article Abstract: Biomass derived from small-diameter, dense, thinning stands is largely underutilized within the European Union, mainly because of in-effective harvesting methods and cutting technology, leading to high supply costs. Therefore, the efficacy of boom-corridor thinning (BCT) and selective thinning (ST) on harvester felling and bunching productivity was compared for the first thinning of whole tree biomass in small-diameter, dense stands. BCT working method is when trees are cut with linear movements of the harvester’s boom reach, along narrow corridors, instead of cutting each tree selectively (ST). Trials were performed in six forest stands, one in Sweden, two in Finland, and three in Slovenia, using the same harvester and operator. A time-and-motion study was carried out in 64 pre-marked study units (32 replications per method), across a variety of stand conditions. The biomass removal for both treatments averaged 40.2 dry t ha -1 and BCT productivity averaged 5.4 dry t PMh -1. For BCT, harvester work time consumption (sec tree -1) and productivity (dry t PMh -1) were on average 27% lower and 16% higher, respectively, compared with ST. The effectiveness of the accumulating felling head technology used could potentially be increased by implementing a feed-roller system when handling excessive tree lengths. Developing dedicated harvesting technology for BCT could further boost productivity, facilitating cost-effective and sustainable utilization of low-value small-diameter tree biomass and replacing fossil resources. Keywords: bioenergy, accumulating felling head, multi-tree handling, silviculture, bioeconomy, forestry Published in DiRROS: 20.04.2022; Views: 719; Downloads: 482
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