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Articles containing the keyword 'forest floor'.

Category: Research article

article id 1615, category Research article
Minna Blomqvist, Päivi Lyytikäinen-Saarenmaa, Tuula Kantola, Maiju Kosunen, Mervi Talvitie, Markus Holopainen. (2016). Impacts of natural enemies and stand characteristics on cocoon mortality of the pine sawfly Diprion pini in a Fennoscandian boreal forest. Silva Fennica vol. 50 no. 5 article id 1615. https://doi.org/10.14214/sf.1615
Highlights: Annual cocoon mortality caused by natural enemies varied between 66% and 80% during the six-year study period, most of it caused by the family Ichneumonidae; Basal area, and coverage of lichen (Lichenes) and lingonberry (Vaccinium vitis-idaea L.) best explained cocoon parasitism and predation; Combination of suitable stand characteristics, abiotic environmental factors, and incomplete control by natural enemies enabled pest species to extend its gradation phase.

We investigated the impact of natural enemies on the cocoon mortality of the common pine sawfly (Diprion pini L.) during a six-year period in eastern Finland. The enemies were classified into parasitoids (insect families Chalcidoidea, Ichneumonidae, and Tachinidae), and predators (birds, small mammals, and insect families Elateridae and Carabidae). The appearance of D. pini was estimated as the intensity of annual defoliation. The impact of stand characteristics on the performance of parasitoids and predators was also investigated. Influence of the natural enemy complex on cocoon mortality of D. pini was nearly stable, but defoliation intensity slowly declined towards the end of the study period. Annual cocoon mortality by natural enemies varied between 66% and 80%. Our results verified that the most significant mortality factors were ichneumonid parasitoids and small mammals. Random Forest classification indicated that stand characteristics, such as basal area, and coverage of lichen (Lichenes) and lingonberry (Vaccinium vitis-idaea L.) affected the performance of parasites and predators. We suggest that a combination of optimal stand characteristics, abiotic environmental factors and mild to moderate control by natural enemies acted as drivers, which drove the pine sawfly population to extended gradation. For future forest health management, detailed information on abiotic and biotic regulating factors, along with long-term monitoring campaigns for conifer sawflies are needed to adapt Fennoscandian forests to altered climatic and silvicultural conditions.

  • Blomqvist, University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Finland ORCID ID: http://orcid.org/0000-0003-2328-8839 E-mail: minna.blomqvist@helsinki.fi (email)
  • Lyytikäinen-Saarenmaa, University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Finland ORCID ID:E-mail: paivi.lyytikainen-saarenmaa@helsinki.fi
  • Kantola, Knowledge Engineering Laboratory, Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA ORCID ID:E-mail: tuula.kantola@helsinki.fi
  • Kosunen, University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Finland ORCID ID:E-mail: maiju.kosunen@helsinki.fi
  • Talvitie, University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Finland ORCID ID:E-mail: mervi.talvitie@dnainternet.net
  • Holopainen, University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Finland ORCID ID:E-mail: markus.holopainen@helsinki.fi
article id 599, category Research article
Chun-Jiang Liu, Carl J. Westman, Hannu Ilvesniemi. (2001). Matter and nutrient dynamics of pine (Pinus tabulaeformis) and oak (Quercus variabilis) litter in North China. Silva Fennica vol. 35 no. 1 article id 599. https://doi.org/10.14214/sf.599
In the mountainous area of North China, a distinguishing feature of climate is the serious drought of spring and the humidity and high temperature of summer by which the litter production and decomposition of forest litter were strongly characterized. We investigated the dynamic and nutrient characteristics of litter in a 30-year-old mixed stand of Chinese pine (Pinus tabulaeformis Carr.) and deciduous orient oak (Quercus variabilis Bl.) and two comparable pure stands. Oak litterfall peaked in November and pine litterfall in December. The oak stand had the largest annual litterfall (347 g m–2) and the forest floor mass (950 g m–2), the mixed stand the second (236 g m–2 and 634 g m–2), and the pine stand the least (217 g m–2 and 615 g m–2). The nutrient return through litterfall and the storage in forest floor followed corresponding order between three stands. The weight loss of pine and oak foliage litter in first year was 25% and 20%. For senesced pine and oak leaves, the translocation rates of N, P and K were 56–83%. Nutrient concentrations were higher in oak leaf litter than pine needle litter, and the concentration of N and Ca appeared to rise while K concentration decreased in both decomposing litter.
  • Liu, Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland ORCID ID:E-mail: cliu@silvia.helsinki.fi (email)
  • Westman, Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Ilvesniemi, Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland ORCID ID:E-mail:

Category: Research note

article id 678, category Research note
Ian A. Nalder, Ross W. Wein. (1998). A new forest floor corer for rapid sampling, minimal disturbance and adequate precision. Silva Fennica vol. 32 no. 4 article id 678. https://doi.org/10.14214/sf.678
We describe an effective and inexpensive device for sampling forest floors. It is based on a rechargeable, battery-powered drill that drives a sharpened steel coring tube. The corer is simple to fabricate, is lightweight (3.5 kg) and can be used easily by one person to obtain intact, natural volume cores of the forest floor. It has been used extensively to obtain samples in 114 boreal forest stands of western Canada. We found that coefficients of variation were typically 30% for forest floor organic matter and bulk density, and tended to be higher in Pinus banksiana stands than in Picea glauca and Populus tremuloides. Ten samples per stand gave adequate precision for a study of forest floor dynamics and autocorrelation did not appear to be a problem with five-metre sampling intervals. In addition to sampling forest floors, the corer has proven suitable for sampling moss and lichen layers and mineral soil down to about 20 cm. A similar powered system can also be used for increment boring of trees.
  • Nalder, University of Alberta, Department of Renewable Resources, 442 Earth Sciences Building, Edmonton, Alberta, Canada T6G 2E3 ORCID ID:E-mail: inalder@gpu.srv.ualberta.ca (email)
  • Wein, University of Alberta, Department of Renewable Resources, 442 Earth Sciences Building, Edmonton, Alberta, Canada T6G 2E3 ORCID ID:E-mail:

Category: Special section

article id 288, category Special section
Björn Berg, Per Gundersen, Cecilia Akselsson, Maj-Britt Johansson, Åke Nilsson, Lars Vesterdal. (2007). Carbon sequestration rates in Swedish forest soils – a comparison of three approaches. Silva Fennica vol. 41 no. 3 article id 288. https://doi.org/10.14214/sf.288

Carbon sequestration rates in forest soil can be estimated using the concept of calculable stable remains in decomposing litter. In a case study of Swedish forest land we estimated C-sequestration rates for the two dominant tree species in the forest floor on top of the mineral soil. Carbon sequestration rates were upscaled to the forested land of Sweden with 23 x 106 ha with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (Karst.) L.). Two different theoretical approaches, based on limit-value for litter decomposition and N-balance for vegetation and SOM gave rates of the same magnitude. For the upscaling, using these methods, 17 000 grids of 5 x 5 km were used.

The ‘limit-value approach’ gave a sequestration of 4.8   106 tons of C, annually sequestered in the forest floor, with an average of 180 kg C ha–1 yr–1 and a range from 40 to 410 kg C ha–1 yr–1. The ‘N-balance approach’ gave an average value of c. 96 kg ha–1 yr–1 and a range from –60 to 360 kg ha–1 yr–1. A method based on direct measurements of changes in humus depth over 40 years, combined with C analyses gave an average rate that was not very different from the calculated rates, viz. c. 180 kg ha–1 yr–1 and a range from –20 to 730 kg ha–1 yr–1. These values agree with forest floor C sequestration rate based on e.g. sampling of chronsequences but differ from CO2 balance measurements.

The three approaches showed different patterns over the country and regions with high and low carbon sequestration rates that were not always directly related to climate.

  • Berg, Dept. of Forest Ecology, University of Helsinki, Finland (present address: Dipartimento Biologia Strutturale e Funzionale, Complesso Universitario, Monte S. Angelo, Napoli, Italy ORCID ID:E-mail: bjorn.berg@helsinki.fi (email)
  • Gundersen, Forest & Landscape Denmark, University of Copenhagen, Denmark ORCID ID:E-mail:
  • Akselsson, Swedish Environmental Research Institute, IVL, Gothenburg, Sweden ORCID ID:E-mail:
  • Johansson, Department of Forest Soils, SLU, Uppsala, Sweden ORCID ID:E-mail:
  • Nilsson, Department of Forest Soils, SLU, Uppsala, Sweden ORCID ID:E-mail:
  • Vesterdal, Forest & Landscape Denmark, University of Copenhagen, Denmark ORCID ID:E-mail:

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