Helmer Belbo. (2010). Comparison of two working methods for small tree harvesting with a multi tree felling head mounted on farm tractor. Silva Fennica vol. 44 no. 3 article id 142. https://doi.org/10.14214/sf.142

Keywords: Norway spruce; cost functions; forest biomass harvesting; multi-tree handling; young stands

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In this study, the efficiency of a small multi-tree felling head, mounted on a farm tractor with a timber trailer was studied, when harvesting small trees for energy in thinnings. Both separate loading and direct loading of the felled trees was studied. Time studies were carried out in a mixed stand of Norway spruce (Picea abies (L.) Karst) and birch (Betula pubescens Ehrh.). The time consumption of the work elements in the different work methods was formulated by regression analysis, where the independent variables were tree size and degree of accumulation. The average size of the harvested trees was 0.035 m3. The time consumption for the harvesting and loading were similar for the two studied methods, 20 minutes per m3 at a tree size of 0.035 m3, but the two methods showed different characteristics for different tree sizes and level of accumulation. The direct loading method had the highest productivity when more than 0.1 m3 were collected in the felling cycle, whereas the separate loading method had the highest productivity when less than 0.05 m3 were collected in the felling cycle. The total effective time consumption for harvesting and forwarding the biomass 300 meters to roadside landing was 27 minutes per m3. The efficiency of the initial felling and collecting of the small trees was the main challenge. Both the harvesting technique and harvesting technology needs further development to provide a feasible production chain for woodfuel from energy thinning.

Belbo, Norwegian Forest and Landscape Institute, Box 115, 1431 Ås, Norway E-mail: helmer.belbo@skogoglandskap.no

Category : Research note

article id 974, category Research note

Kristina Ahnlund Ulvcrona, Lars Karlsson, Ingegerd Backlund, Urban Bergsten. (2013). Comparison of silvicultural regimes of lodgepole pine (Pinus contorta) in Sweden 5 years after precommercial thinning. Silva Fennica vol. 47 no. 3 article id 974. https://doi.org/10.14214/sf.974

Keywords: direct seeding; forest production; corridor thinning; biomass harvest; PCT

Highlights: Management regimes can serve different purposes such as biomass production, pulp and timber production or a combination of those; 30 tons biomass or 38–45 m³ stem volume ha^–1 could be derived by schematic corridor thinning (70%) at year 20; Producing large amounts of biomass early in the rotation period does not exclude a conversion into pulp and timber production.

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Early effects (stem volume, mean diameter at breast height weighted against basal area (Dgv) (Dgv), biomass and damage frequency) of different silvicultural regimes 18-19 years after direct seeding of lodgepole pine in northern Sweden were analysed. A Conventional regime, (i) precommercial thinning (PCT) to 2200 stems ha^-1, was compared to: (ii) High biomass production (15 300 stems ha^-1, no PCT) with and without corridor thinning at year 20, (iii) production of Large dimension trees (PCT to 1700 stems ha^-1), (iv), Combined high biomass production and production of conventional round wood (PCT to 4500 stems ha^-1). PCT was done 15 yrs after direct seeding for all PCT treatments. Local biomass functions showed that the regimes aiming at High biomass production displayed ca 144-157% more biomass and 134-143% more stem volume than the Conventional and Large dimension regimes (ca 21 tons and 31 m³ ha^-1). Dgv for the 1000 (9.2 cm) and 2000 (8.3 cm) largest trees ha^-1 appeared unaffected by regime. By schematic corridor thinning (70% of the total area) at year 20 in the High biomass regime, 27-32 tons of biomass ha^-1 and 38-45 m³ ha^-1 could be derived while still having a Dgv of the 1000 largest trees ha^-1 of about 8 cm. Therefore, this study indicates that it is possible to produce and harvest large amounts of biomass and stem volume early in the rotation period without excluding later pulp and timber production. This initial regime comparison should be continued over time.

Ahnlund Ulvcrona, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: kristina.ulvcrona@slu.se
Karlsson, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: lars.karlsson@slu.se
Backlund, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: ingegerd.backlund@slu.se
Bergsten, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: urban.bergsten@slu.se

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