Articles by Harri Mäkinen

Possibilities of distance-independent and -dependent competition indices to describe the competition stress of an individual tree was studied in Southern Finland. Five half-sib open-pollinated families and one check lot of Scots pine (Pinus sylvestris L.) was used as study material in order to analyse competitive interactions of crown form and stand density variation. Almost all competition indices correlated strongly with radial increment. Thus distance-independent indices were adequate to describe competition in young row plantations, where distance effects between trees were implicitly eliminated. Correlations between indices and height increment were not significant. Along with the increase in competition, the width and length of the crown and the diameter increment of the stem of some narrow-crowned families decreased slowly compared to wide-crowned families.

• Mäkinen, E-mail: hm@mm.unknown

After a decades-long increasing trend, the recent results of the National Forest Inventory (NFI) reported a decline of forest growth in North Finland. The aim of this study was to assess climatic and reproduction influences behind the growth decline. We used tree-ring data that had been collected by NFI using systematic sampling. The tree-ring width series were detrended using the regional curve standardisation (RCS) removing age-related trends. The resulting tree-ring indices of Scots pine (Pinus sylvestris L.) showed decadal variations with low increment in the 1990s, and high increment in the 1980s and the early years of the current century. Thereafter, a prolonged growth reduction for pine started both on the mineral soil sites and peatlands. The tree-ring indices of Norway spruce (Picea abies (L.) Karst.) had less pronounced decadal variations and no trend-like reduction over the last 15 years. High spring and summer temperatures were found to enhance radial growth, but high winter temperatures were related to low growth for pine and spruce in the following summer. Temperature variation, accompanied by variables indicating years of drought and intensive flowering, accounted for 34% annual growth variance of pine and 21–44% for spruce. Thus, the results imply that climatic factors may have to some extent contributed to the recent growth reduction of pine. Due to its ecological and economic consequences growth decline needs to be further monitored and investigated. Moreover, analyses of stand and age structure, potentially affecting the growth decline, were beyond the scope of this paper, but also warrant further investigation.

• Mäkinen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki https://orcid.org/0000-0002-1820-6264 E-mail: harri.makinen@luke.fi
• Nöjd, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki E-mail: pekka.nojd@luke.fi
• Helama, Natural Resources Institute Finland (Luke), Ounasjoentie 6, 96200 Rovaniemi, Finland https://orcid.org/0000-0002-9777-3354 E-mail: samuli.helama@luke.fi

Ageing and competition reduce trees’ ability to capture resources, which predisposes them to death. In this study, the effect of senescence on the survival probability of Norway spruce (Picea abies (L.) Karst.) was analysed by fitting alternative survival probability models. Different model formulations were compared in the dataset, which comprised managed and unmanaged plots in long-term forest experiments in Finland and Norway, as well as old-growth stands in Finland. Stand total age ranged from 19 to 290 years. Two models were formulated without an age variable, such that the negative coefficient for the squared stem diameter described a decreasing survival probability for the largest trees. One of the models included stand age as a separate independent variable, and three models included an interaction term between stem diameter and stand age. According to the model including stand age and its interaction with stem diameter, the survival probability curves could intersect each other in stands with a similar structure but a different mean age. Models that did not include stand age underestimated the survival rate of the largest trees in the managed stands and overestimated their survival rate in the old-growth stands. Models that included stand age produced more plausible predictions, especially for the largest trees. The results supported the hypothesis that the stand age and senescence of trees decreases the survival probability of trees, and that the ageing effect improves survival probability models for Norway spruce.

• Siipilehto, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland E-mail: jouni.siipilehto@luke.fi
• Mäkinen, Natural Resources Institute Finland (Luke), Production systems, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland https://orcid.org/0000-0002-1820-6264 E-mail: harri.makinen@luke.fi
• Andreassen, Norwegian Institute of Bioeconomy Research (NIBIO), NO-1431 Ås, Norway E-mail: kjellandreassen@gmail.com
• Peltoniemi, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland https://orcid.org/0000-0003-2028-6969 E-mail: mikko.peltoniemi@luke.fi

Despite the numerous studies on year-to-year variation of tree growth, the physiological mechanisms controlling annual variation in growth are still not understood in detail. We studied the applicability of data-driven approach i.e. different regression models in analysing high-dimensional data set including continuous and comprehensive measurements over meteorology, ecosystem-scale water and carbon fluxes and the annual variation in the growth of app. 50-year-old Scots pine stand in southern Finland. Even though our dataset covered only 16 years, it is the most extensive collection of interactions between a Scots pine ecosystem and atmosphere. The analysis revealed that height growth was favoured by high water potential of the tree and carbon gain during the bud forming period and high water potential during the elongation period. Diameter growth seemed to be favoured by a winter with high precipitation and deep snow cover and a spring with high carbon gain. The obtained models had low generalization performance and they would require more evaluation and iterative validation to achieve credibility perhaps as a mixture of data-driven and first principle modeling approaches.

• Kulmala, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: liisa.kulmala@helsinki.fi
• Žliobaitė, Aalto University, Department of Computer Science and Helsinki Institute for Information Technology, P.O. Box 11000, FI-00076 Aalto, Finland; University of Helsinki, Department of Geosciences and Geography, P.O. Box 64, FI-00014 University of Helsinki, Finland E-mail: zliobaite@gmail.com
• Nikinmaa, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: eero.nikinmaa@helsinki.fi
• Nöjd, Natural Resources Institute Finland (Luke), Bio-based business and industry, Tietotie 2, FI-02150 Espoo, Finland E-mail: pekka.nojd@luke.fi
• Kolari, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland; University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Finland E-mail: pasi.kolari@helsinki.fi
• Kabiri Koupaei, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: kourosh.kabiri@helsinki.fi
• Hollmén, Aalto University, Department of Computer Science and Helsinki Institute for Information Technology, P.O. Box 11000, FI-00076 Aalto, Finland; University of Helsinki, Department of Geosciences and Geography, P.O. Box 64, FI-00014 University of Helsinki, Finland E-mail: jaakko.hollmen@aalto.fi
• Mäkinen, Natural Resources Institute Finland (Luke), Bio-based business and industry, Tietotie 2, FI-02150 Espoo, Finland E-mail: harri.makinen@luke.fi

• Jyske, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: tuula.jyske@metla.fi
• Mäkinen, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: hm@nn.fi
• Saranpää, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ps@nn.fi