Current issue: 55(4)

Under compilation: 55(5)

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Silva Fennica 1926-1997
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Acta Forestalia Fennica
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Articles by Heli Viiri

Category: Research article

article id 10528, category Research article
Jaana Luoranen, Heli Viiri. (2021). Comparison of the planting success and risks of pine weevil damage on mineral soil and drained peatland sites three years after planting. Silva Fennica vol. 55 no. 4 article id 10528. https://doi.org/10.14214/sf.10528
Highlights: The planting success was poorer on peatland sites than on mineral soil; Dense ground vegetation cover is more probable on peatland than on mineral soil; No differences in pine weevil feeding damage on mineral soil and peatland were found; Cultivated mineral soil reduced the vegetation cover, feeding damage and seedling mortality.

Over 20% of regeneration operations will be on drained peatland in the next decade in Finland. There are only a few studies comparing the planting success and the risk of pine weevil (Hylobius abetis (L.) feeding damage on mineral soil and drained peatland. Thirty sites planted with Norway spruce (Picea abies (L.) H. Karst.) container seedlings in 2009 in Southern and Central Finland were inventoried three growing seasons after planting. Prediction models for the probability of survival, pine weevil damage and the presence of ground vegetation cover were done separately for peatland and mineral soil sites. The planting success was 17% lower on peatland sites (1379 surviving seedlings ha–1) than on mineral soil (1654 seedlings ha–1). The factors explaining the survival were the ground vegetation cover and type of the planting spot on the peatland, and the ground vegetation cover on mineral soil. On mineral soil, 76% of the planting spots were on cultivated mineral soil while on peatland only 28% of the seedlings were planted on similar spots. There were also fewer seedlings that were surrounded by dense ground vegetation on mineral soil (4%) than on peatland (14%). Pine weevil feeding damage did not differ significantly on peatland (23%) or mineral soil (18%). The more time there was from clear-cutting, the more the probability of pine weevil feeding damage was reduced on both soil classes. Additionally, cover vegetation in the vicinity of the seedlings increased on mineral soil. Cultivated planting spots, especially those covered by mineral soil, prevented pine weevil feeding and reduced the harmful effects of vegetation on the seedlings both on mineral soil and peatland.

Category: Research note

article id 10262, category Research note
Markus Melin, Heli Viiri, Olli-Pekka Tikkanen, Riku Elfving, Seppo Neuvonen. (2020). From a rare inhabitant into a potential pest – status of the nun moth in Finland based on pheromone trapping. Silva Fennica vol. 54 no. 1 article id 10262. https://doi.org/10.14214/sf.10262
Highlights: The nun moth is a significant defoliator of coniferous forests in Central-Europe; In Finland, the populations have grown and expanded northwards; Pheromone trapping confirmed the species’ presence throughout central- and southern Finland; The risk of the nun moth becoming a pest for Finland is real as the area offers endless habitats, and climatic conditions are becoming more favourable; This note describes the results from the first nun moth surveys conducted in 2018 and 2019.

Forests are affected by climate change in various ways. This includes abiotic factors such as droughts, but also biotic damage by pest insects. There are numerous examples from cases where pest insects have benefitted from longer growing seasons or from warmer summers. Similarly, new pest insects have been able to expand their range due to climatic conditions that have changed from hostile to tolerable. Such seems to be the case with the nun moth (Lymantria monacha), an important defoliator of coniferous trees in Europe. For centuries, the species has had massive outbreaks across Central-Europe, while it has been a rare inhabitant in Northern Europe. Recently, the nun moth population in Finland has not only expanded in range, but also grown more abundant. This research note describes the results from the first years (2018–2019) of a monitoring program that is being conducted with pheromone traps across central and southern Finland. So far, the northernmost individuals were trapped near the 64 N degrees. However, there were more southern locations where no moths were trapped. The species was present in every trapping site below the latitude of 62 N degrees. More importantly, at some sites the abundance of the nun moth suggested that local forest damage may already occur. Given the current climatic scenarios for Fennoscandia, it is likely that the nun moth populations will continue to grow, which is why systematic surveys on their abundance and range expansions will be topical.

  • Melin, Natural Resources Institute Finland, Yliopistokatu 6b, FI-80100 Joensuu, Finland ORCID ID: https://orcid.org/0000-0001-7290-9203 E-mail: markus.melin@luke.fi (email)
  • Viiri, Natural Resources Institute Finland, Yliopistokatu 6b, FI-80100 Joensuu, Finland; UPM-Kymmene Oyj, UPM Forest, Åkerlundinkatu 11 B, FI-33100 Tampere, Finland ORCID ID:E-mail: heli.viiri@upm.com
  • Tikkanen, University of Eastern Finland, School of Forest Sciences, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: olli-pekka.tikkanen@uef.fi
  • Elfving, Natural Resources Institute Finland, Yliopistokatu 6b, FI-80100 Joensuu, Finland; University of Oulu, Department of Biology, Pentti Kaiteran katu 1, FI-90014 Oulu, Finland ORCID ID:E-mail: riku.elfving@gmail.com
  • Neuvonen, University of Turku, Biodiversity Unit, Kevo Subarctic Research Institute, FI-20014 Turku, Finland ORCID ID:E-mail: seppo.neuvonen@utu.fi
article id 71, category Research note
Jaana Luoranen, Heli Viiri. (2012). Soil preparation reduces pine weevil (Hylobius abietis L.) damage on both peatland and mineral soil sites one year after planting. Silva Fennica vol. 46 no. 1 article id 71. https://doi.org/10.14214/sf.71
We studied pine weevil (Hylobius abietis (L.)) feeding damage to Norway spruce and Scots pine seedlings planted in regeneration areas located on peatlands or on mineral soil sites in Southern and Central Finland. The survey included two planting years and a total of 60 regeneration areas (40 areas on peatlands and 20 on mineral soil sites). Some sites classified as peatland were as transformed or transforming drained peatlands that also contained mineral soil on a prepared surface. The soil preparation method, type of surface material around a seedling, pine weevil, vole-induced or other damage and the health of each seedling were observed in systematically selected circular sample plots. There was slightly more pine weevil damage on peatland than on mineral soil sites. More seedlings were damaged on unprepared peat and humus than on a prepared surface. Seedlings surrounded by a prepared surface had a slightly greater risk of being gnawed by pine weevil when planted on prepared peat compared to planting on prepared mineral soil. Vole damage was observed only in one region during one year. Mounded areas had slightly less vole damage than patched areas. In order to reduce damage caused by pine weevils and voles, it is important to scarify the regeneration area properly before insecticide-treated seedlings are planted. Mounding and patching are recommended so that seedlings can be planted in mineral soil whenever possible, even in the case of peatlands.
  • Luoranen, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: jaana.luoranen@metla.fi (email)
  • Viiri, Finnish Forest Research Institute, Joensuu Unit, Joensuu, Finland ORCID ID:E-mail:

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