Articles by Sauli Valkonen

Mixed linear models were constructed to describe the height development of Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) advance growth after release cutting. The models related density of the overstory, time elapsed since release cutting and tree size with annual height increment. Parameters of preliminary models were estimated from a limited data set to judge the feasibility of the approach for further studies.

The PDF includes an abstract in Finnish.

• Koistinen, E-mail: ek@mm.unknown
• Valkonen, E-mail: sv@mm.unknown

The aim of this study was to experimentally test the most favourable seeding times for Scots pine (Pinus sylvestris L.), and to compare Scots pine and lodgepole pine (Pinus contorta Douglas ex Loudon) in respect to suitable seeding times and site factors. The experimental area was located in Sodankylä, Central Finnish Lapland. Generalized linear mixed effects models with binomial distribution assumption were applied to model the presence or absence of a seedling at a seeding point. The study shows that in addition to spring and early summer, direct seeding of Scots pine can also be carried out during late autumn or even early winter (October and November) in northern Fennoscandia. On the contrary, seeding in late summer and early autumn (August and September) is much less successful and cannot be recommended as such, but can be used if the amount of seeding material is increased to compensate the loss. There is more flexibility for lodgepole pine for which the proper seeding period seems to be from spring through to late autumn. Whether lodgepole pine seeds were stratified or not had no statistically significant effect on regeneration success. Our results clearly indicate that lodgepole pine is less susceptible to unfavourable site and soil factors than Scots pine. Our results give support to extend the period of direct seeding from the present early summer to another period in late autumn and even early winter.

• Hyppönen, Natural Resources Institute Finland (Luke), Ounasjoentie 6, FI-96200 Rovaniemi, Finland E-mail: mikkokthypponen@gmail.com
• Hallikainen, Natural Resources Institute Finland (Luke), Ounasjoentie 6, FI-96200 Rovaniemi, Finland https://orcid.org/0000-0001-5384-8265 E-mail: ext.ville.hallikainen@luke.fi
• Bergsten, Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences (SLU), Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: burskog@gmail.com
• Winsa, Natural Resources Institute Finland (Luke), Ounasjoentie 6, FI-96200 Rovaniemi, Finland E-mail: hans.winsa@gmail.com
• Miina, Natural Resources Institute Finland (Luke), Yliopistokatu 6 B, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-8639-4383 E-mail: jari.miina@luke.fi
• Valkonen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790, Helsinki, Finland https://orcid.org/0000-0002-2879-4821 E-mail: sauli.valkonen@luke.fi
• Helenius,  Natural Resources Institute Finland (Luke), Tietotie 4, FI-31600 Jokioinen, Finland E-mail: psjhelenius@elisanet.fi
• Jaskari, Natural Resources Institute Finland (Luke), Ounasjoentie 6, FI-96200 Rovaniemi, Finland E-mail: ejaskari@gmail.com
• Rautio, Natural Resources Institute Finland (Luke), Ounasjoentie 6, FI-96200 Rovaniemi, Finland https://orcid.org/0000-0003-0559-7531 E-mail: pasi.rautio@luke.fi

• Puttonen, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: pasi.puttonen@helsinki.fi
• Valkonen, Finnish Forest Research Institute, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: sauli.valkonen@metla.fi