Johanna Jetsonen, Annamari Laurén, Heli Peltola, Katariina Laurén, Samuli Launiainen, Marjo Palviainen. (2025). Volume growth responses of Scots pine and Norway spruce to nitrogen fertilization: quantitative synthesis of fertilization experiments in Finland. Silva Fennica vol. 59 no. 1 article id 24041. https://doi.org/10.14214/sf.24041

Keywords: precipitation; growth response; mineral soils; site fertility

Highlights: Volume growth responses increased linearly with the applied nitrogen (N) dose up to 200 kg N ha^–1; Precipitation, site fertility, and time since fertilization affected the growth responses; Volume growth response to nitrogen fertilization was larger for Scots pine than for Norway spruce; Results can support planning of environmentally responsible and economically viable precision fertilization.

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The effects of nitrogen (N) fertilization on tree growth have been studied widely in boreal forests in Finland, but a quantitative synthesis is still lacking. We performed a quantitative synthesis on volume growth responses to N fertilization in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands in experiments established on mineral soils across Finland. Our study employed findings of 9 published studies including 108 Scots pine and 57 Norway spruce observations covering a wide range of N fertilization treatments, as well as forest stand- and climatic conditions. Based on these observations, we built linear mixed models to describe the N fertilization-induced annual volume growth response of Scots pine and Norway spruce stands. Our models showed that the N dose was the best predictor for volume growth response, and the growth response increased linearly with increasing N dose for both tree species. The volume growth responses also increased along with an increase in mean annual precipitation. The annual volume growth response decreased with the time since fertilization. For Scots pine, the best model also contained site fertility; increase in site fertility increased the volume growth response. These findings emphasize the need for site-specific precision fertilization schemes to sustainably improve growth and carbon sequestration of boreal forests.

Jetsonen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0009-0006-4878-8951 E-mail: johanna.jetsonen@helsinki.fi
Laurén, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland; Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0002-6835-9568 E-mail: annamari.lauren@helsinki.fi
Peltola, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi
Laurén, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland; University of Helsinki, Faculty of Medicine, Haartmaninkatu 8, 00290 Helsinki, Finland https://orcid.org/0009-0009-4677-9826 E-mail: katariina.lauren@helsinki.fi
Launiainen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland https://orcid.org/0000-0001-6611-6573 E-mail: samuli.launiainen@luke.fi
Palviainen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0000-0001-9963-4748 E-mail: marjo.palviainen@helsinki.fi

article id 10494, category Research article

Hannu Hökkä, Ari Laurén, Leena Stenberg, Samuli Launiainen, Kersti Leppä, Mika Nieminen. (2021). Defining guidelines for ditch depth in drained Scots pine dominated peatland forests. Silva Fennica vol. 55 no. 3 article id 10494. https://doi.org/10.14214/sf.10494

Keywords: Pinus sylvestris; forest management; peatland; drainage; ditch network maintenance; process model; water table

Highlights: Process-based hydrological model was applied to drained peatland forests representing a wide range of conditions in Finland; Ditch depth keeping the median July–August water table below 0.35 m was defined; Ditch depth depended on climatic conditions, stand volume, peat properties, and ditch spacing; Shallower ditches than recommended in practice proved to be sufficient in most situations.

Abstract | Full text in HTML | Full text in PDF | Author Info

We used a process-based hydrological model SUSI to improve guidelines for ditch network maintenance (DNM) operations on drained peatland forests. SUSI takes daily weather data, ditch depth, strip width, peat properties, and forest stand characteristics as input and calculates daily water table depth (WTD) at different distances from ditch. The study focuses on Scots pine (Pinus sylvestris L.) dominated stands which are the most common subjects of DNM. Based on a literature survey, and consideration of the tradeoffs between forest growth and detrimental environmental impacts, long term median July–August WTD of 0.35 m was chosen as a target WTD. The results showed that ditch depths required to reach such WTD depends strongly on climatic locations, stand volume, ditch spacing, and peat thickness and type. In typical ditch cleaning areas in Finland with parallel ditches placed about 40 m apart and tree stand volumes exceeding 45 m³ ha^–1, 0.3–0.8 m deep ditches were generally sufficient to lower WTD to the targeted depth of 0.35 m. These are significantly shallower ditch depths than generally recommended in operational forestry. The main collector ditch should be naturally somewhat deeper to permit water outflow. Our study brings a firmer basis on environmentally sound forestry on drained peatlands.

Hökkä, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: hannu.hokka@luke.fi
Laurén, University of Eastern Finland, Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ari.lauren@uef.fi
Stenberg, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: leena.stenberg@luke.fi
Launiainen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: samuli.launiainen@luke.fi
Leppä, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: kersti.leppa@luke.fi
Nieminen, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: mika.nieminen@luke.fi

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