Silva Fennica vol. 57 no. 1 | 2023

• de Miguel, University of Lleida, Av. Alcalde Rovira Roure 191, 25198 Lleida, Spain; Joint Research Unit CTFC – AGROTECNIO – CERCA, Ctra de Sant Llorenç de Morunys, km 2, 25280 Solsona, Spain https://orcid.org/0000-0002-9738-0657 E-mail: sergio.demiguel@udl.cat

• Nirhamo, School of Forest Sciences, University of Eastern Finland, Joensuu, Finland https://orcid.org/0000-0002-1487-533X E-mail: aleksi.nirhamo@uef.fi
• Pykälä, Finnish Environment Institute, Helsinki, Finland https://orcid.org/0000-0002-7566-9310 E-mail: juha.pykala@syke.fi
• Jääskeläinen, Kuopio Museum of Natural History, Kuopio, Finland E-mail: jaaskimmo@gmail.com
• Kouki, School of Forest Sciences, University of Eastern Finland, Joensuu, Finland https://orcid.org/0000-0003-2624-8592 E-mail: jari.kouki@uef.fi

• Kuusinen, Department of Built Environment, School of Engineering, Aalto University, P.O. Box 14100, FI-00076 Aalto, Finland https://orcid.org/0000-0002-8063-1739 E-mail: nea.kuusinen@aalto.fi
• Hovi, Department of Built Environment, School of Engineering, Aalto University, P.O. Box 14100, FI-00076 Aalto, Finland https://orcid.org/0000-0002-4384-5279 E-mail: aarne.hovi@aalto.fi
• Rautiainen, Department of Built Environment, School of Engineering, Aalto University, P.O. Box 14100, FI-00076 Aalto, Finland https://orcid.org/0000-0002-6568-3258 E-mail: miina.a.rautiainen@aalto.fi

The sustainability of native forests in Sub-Saharan Africa depends on the diversification of sources to generate bioenergy, and Eucalyptus spp. wood has been highlighted. However, the determination of energy quality parameters has been a challenge to enable plantation wood to generate energy. The research assessed the ash content of radial and longitudinal samples of Eucalyptus grandis (Hill) clone with different ages and growth sites. Samples were collected in three pre-established plots in the center of Mozambique. Five trees were cut down in each plot and six discs were removed from each tree. Grinded samples with <0.5 mm particle size were generated from the heartwood and sapwood of each disk to determine the ash content. Wood from 7-year-olds had a higher ash content compared to 9-year-olds. The two sample plots differed from each other in terms of wood ash content. Heartwood samples had smaller ash content than sapwood samples. In general, the ash content of the intermediate positions was lower than those from the base and top of the stem, for both radial sections. No conclusive differences were found between samples from the base and the top of the trees, indicating that the material from the top of the trees can also be used as wood fuel. Ash content can be a considerable parameter to assess the quality of the wood of Eucalyptus spp. as a fuel.

• Mogeia, Universidade Lúrio, Faculdade de Ciências Agrárias, Departamento de Silvicultura e Maneio [Lurio University, Faculty of Agricultural Sciences, Department of Forestry and Management], Campus de Wanaango, EN733, Km 42, Unango, Niassa, Mozambique E-mail: smogeia@unilurio.ac.mz
• Manhiça, Centro de Investigação Florestal, [Forestry Research Center], Marracuene, EN1, Maputo província, Mozambique E-mail: albertomanhica@gmail.com
• Egas, Universidade Eduardo Mondlane, Faculdade de Agronomia e Engenharia Florestal, Departamento de Florestas, [Eduardo Mondlane University, Faculty of Agronomy and Forestry Engineering, Department of Forests], Av. Julius Nyerere, Maputo cidade, Mozambique E-mail: aegas8@gmail.com

In southern Lapland, 70% of drained peatland forests have a peat layer thickness of less than one metre. On these sites, the question is how the subsoil under the peat affects groundwater level and thus timber harvesting. The aim of this study was to investigate the effect of the peat layer (<1 m) and subsoil on the groundwater level and its variation during the growing season (non-frost) by modelling the factors affecting water level. In sandy soils, the groundwater level rose by 20 cm when the peat layer thickness increased from 20 to 70 cm. In silty soils the effect of the peat thickness on groundwater remained minor. When the subsoil was sand or coarser, the groundwater level was usually deeper than when it was silty or finer. The effect of stand volume (m^–3 ha^–1) on the groundwater level was rather weak albeit significant. The model explained a significant part of the groundwater surface variation, with a marginal coefficient of determination (R²) of 68%. It seems that the rutting of roads could be avoided in late summer if the precipitation is remarkably lower during that period, or if the subsoil is sandy with thin peat layer on top of it. Because the groundwater level affects the load-bearing capacity of timber-harvesting machinery, it is important to study this issue in more detail in the future.

• Hiltunen, Lapland University of Applied Sciences, Jokiväylä 11, FI-96300 Rovaniemi, Finland E-mail: oivah@student.uef.fi
• Hallikainen, Natural Resources Institute Finland, Ounasjoentie 6, FI-96300 Rovaniemi, Finland E-mail: ville.hallikainen@luke.fi
• Palander, The University of Eastern Finland, Faculty of Science, Forestry and Technology, P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0000-0002-9284-5443 E-mail: teijo.s.palander@uef.fi

Our research aimed to quantify and evaluate the stress loading of drivers by monitoring the loading of the radial extensor muscle at the wrist joint (musculus extensor carpi radialis) when they drove different types of timber trucks. We monitored changes in the electric potential of skeletal muscles with electromyographic measurements and measurements of changes of heart rate using the Biofeedback 2000 ^x-pert device. The drivers were observed throughout their work shifts during normal operation of logging trucks and logging trucks with trailers. As a reference, muscle load was measured when driving a passenger car. We evaluated the normality of the measured data and obtained descriptive statistics from the individual measurements. The differences in stress load associated with driving the different types of vehicles increased whilst driving on lower-class roads. Results showed a high stress load for drivers of loaded vehicles when driving on narrow roads. It was more challenging to control a loaded logging truck with a trailer than driving a logging truck, with the difference in muscular loading reaching 22.5%. Driving a logging truck with a trailer produced 46.5% more muscle loading compared to driving a loaded passenger car. For preventive health and safety reasons, it would be reasonable to alternate between drivers when operating various vehicles, thus minimizing the development of possible health issues.

• Škvor, Department of Forestry Technologies and Construction, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6 - Suchdol, Czech Republic https://orcid.org/0000-0001-7540-4761 E-mail: skvorp@fld.czu.cz
• Jankovský, Department of Forestry Technologies and Construction, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6 - Suchdol, Czech Republic E-mail: jankovskym@fld.czu.cz
• Natov, Department of Forestry Technologies and Construction, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6 - Suchdol, Czech Republic E-mail: natov@fld.czu.cz
• Dvořák, Department of Forestry Technologies and Construction, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6 - Suchdol, Czech Republic https://orcid.org/0000-0002-5986-8002 E-mail: dvorakj@fld.czu.cz