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Articles by Juha Siitonen

Category : Article

article id 5431, category Article

Juha Siitonen. (1990). Potential forest pest beetles conveyed to Finland on timber imported from the Soviet Union. Silva Fennica vol. 24 no. 3 article id 5431. https://doi.org/10.14214/sf.a15585

Keywords: Finland; forest pests; timber trade; Scolytidae; Soviet Union; pest introduction; timber import

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Coniferous timber imported by rail from the Soviet Union in Finland was studied for the presence of potential forest and timber pest beetles. Systematic samples of fourteen lots of pine pulpwood were examined. Seven of the lots originated from the European parts of the Soviet Union and seven from Siberia. 23 species of Scolytidae and about 18 other phloeophagous species were found including three species new for Finland: Phaenops guttulata (Buprestidae), Ips subelongatus and Orthotomicus erosus (Scolytidae).

The PDF includes an abstract in Finnish.

Siitonen, E-mail: js@mm.unknown

Category : Research article

article id 216, category Research article

Juha Siitonen, Jenni Hottola, Auli Immonen. (2009). Differences in stand characteristics between brook-side key habitats and managed forests in southern Finland. Silva Fennica vol. 43 no. 1 article id 216. https://doi.org/10.14214/sf.216

Keywords: dead wood; woodland key habitats; stand structure; CWD; WKH; Forest Act

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Preservation of small habitat patches termed as “woodland key habitats” or “especially important habitats” in the Finnish Forest Act has become an integral part of biodiversity-oriented forest management. Forest Act habitats belong to particular habitat types defined in the act, and they are supposed to have natural-like stand characteristics. However, very little is known about the actual stand structure in the designated habitats. Our aim was to compare stand characteristics between brook-side key habitats and comparable managed forests as controls. Seven study areas were selected from four regions across southern Finland. Within each study area ten key habitats and ten controls (140 stands) were randomly selected. Living and dead trees and cut stumps were measured in each stand within a 0.2 ha plot. The average degree of previous cutting was significantly lower whereas the volume of dead wood, volume of deciduous trees, and stand diversity were each significantly higher in key habitats than controls. The average volume of dead wood was 11.7 m³ ha^–1 in key habitats and 6.5 m³ ha^–1 in controls. However, there was considerable variation among individual stands, and a large part of key habitats could not be distinguished from randomly selected control stands with respect to stand characteristics. The preservation of natural brook channels with their immediate surroundings is undoubtedly important for maintaining aquatic and semiaquatic biodiversity. Nevertheless, when complementing the forest conservation network in the future, main emphasis in selecting potentially valuable stands should be placed on important structural features such as dead wood and old trees.

Siitonen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi
Hottola, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jh@nn.fi
Immonen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ai@nn.fi

article id 410, category Research article

Jouni Siipilehto, Juha Siitonen. (2004). Degree of previous cutting in explaining the differences in diameter distributions between mature managed and natural Norway spruce forests. Silva Fennica vol. 38 no. 4 article id 410. https://doi.org/10.14214/sf.410

Keywords: Picea abies; stand structure; naturalness; Johnson’s SB distribution

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The degree of naturalness was assessed in 37 mature (stand age 80 198 yrs) Norway spruce dominated stands located in southern Finland by measuring the number (0 610 ha–1) and basal area (0 33 m2 ha–1) of cut stumps. The Johnson’s SB distribution was fitted for living spruce trees to describe the dbh-frequency and basal area-dbh distributions. Regression models were constructed for predicting the parameters of the SB distribution using traditional stand parameters (median diameter, basal area, stem number) and the cut stump variables (number, basal area). Stump variables improved the models and enabled to explain the differences in diameter distributions between stands with varying intensity of past cutting. Model for basal area-dbh distribution was more accurate than dbh-frequency model in terms of regression statistics, but less accurate in terms of generated stand variables. The number and basal area of cut stumps seem to be useful and simple measures of stand naturalness which have potential uses in stand modelling and biodiversity-oriented forestry planning.

Siipilehto, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi
Siitonen, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi

article id 554, category Research article

Seppo Rouvinen, Timo Kuuluvainen, Juha Siitonen. (2002). Tree mortality in a Pinus sylvestris dominated boreal forest landscape in Vienansalo wilderness, eastern Fennoscandia. Silva Fennica vol. 36 no. 1 article id 554. https://doi.org/10.14214/sf.554

Keywords: dead wood; disturbance dynamics; spatial pattern analysis; mortality agent; forest structure; temporal variation

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Tree mortality and its causes and spatial pattern were examined along four transects (width 40 m, length 2550–3960 m), with a total length of 12 190 m and area of 48.8 ha, in a Pinus sylvestris L. dominated, boreal forest landscape. Tree mortality was determined within a time window of 3 years by identifying those trees (dbh ≥ 10 cm) along the transects that fitted into one of the three categories: 1) current mortality: trees that had died during the year of survey (1998), 2) recent mortality: trees that had died during the year (1997) before the survey year, and 3) predicted mortality: trees that were expected to die during the year (1999) following the survey year. Long-term tree mortality was studied on 10 plots (20 m x 100 m) by dating 87 dead trees using dendrochronological methods. The mean current mortality was 1.4 m3 ha–1 (3.7 trees ha–1). Both the recent and predicted mortalities were also 1.4 m3 ha–1. Mortality was, on the average, higher on peatlands than on mineral soils. The highest mortality was found within an area recently flooded by beavers. Over half of the examined trees (52%) were judged to die without any visible signs of an external abiotic cause. At the landscape scale, tree mortality was continuous although somewhat aggregated in space. Of the 66 dated standing dead Pinus trees, 23 (35%) had died during the 19th century and two during the 18th century, demonstrating that dead Pinus can remain standing for long periods of time before falling. Our results show that autogenic mortality of individual trees or small groups of trees was the predominant mode of disturbance in this Pinus dominated landscape.

Rouvinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: seppo.rouvinen@forest.joensuu.fi
Kuuluvainen, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland E-mail: tk@nn.fi
Siitonen, Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi

Category : Research note

article id 1145, category Research note

Juha Siitonen. (2014). Ips acuminatus kills pines in southern Finland. Silva Fennica vol. 48 no. 4 article id 1145. https://doi.org/10.14214/sf.1145

Keywords: tree mortality; Scots pine; Ips acuminatus; Phaenops cyanea; drought

Highlights: Recently dead pines colonized by Ips acuminatus were frequently found in southern Finland, in a region where the species was thought to be absent; Colonized trees were typically large (average DBH 30 cm), located at open spots in pine-dominated stands, often forming groups of several trees; The damages may be a consequence of dry and hot summers during the 2000s.

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

Recently dead Scots pines (Pinus sylvestris L.) apparently killed by Ips acuminatus (Gyllenhal) were observed in Sipoo, southern Finland, in summer 2013. This record was unexpected and in contradiction with what is currently known about the distribution and aggressiveness of the species in Finland. The aim of this study was to survey a larger area in Uusimaa region, to find out whether I. acuminatus occurs frequently in recently dead pines, and whether inhabited trees share some common tree- or site-level characteristics. Galleries of I. acuminatus were found in most of the studied trees. A total of 96 inhabited trees were found in 21 separate sites. Colonized pines were typically large (average DBH 30 ± 9 cm) trees located in relatively open pine-dominated heathland stands at half-open, sun-exposed spots. The whole upper part of the trunk with thin bark was usually occupied. Galleries of Tomicus piniperda L. or T. minor Hartig occurred only in few cases in the same trees, indicating that the trees had died later in the summer. Galleries of the jewel beetle Phaenops cyanea F. were found in 13 trees. Trees colonized by I. acuminatus often occurred as small groups, with generally 1–12 trees (average 3 trees), but in one exceptional group there were no less than 35 trees. It is possible that the hot and dry summers during the 2000s have increased the susceptibility of pines to insect damage, and have contributed to a population growth of I. acuminatus.

Siitonen, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi

Category : Discussion article

article id 572, category Discussion article

Timo Kuuluvainen, Kaisu Aapala, Petri Ahlroth, Mikko Kuusinen, Tapio Lindholm, Tapani Sallantaus, Juha Siitonen, Harri Tukia. (2002). Principles of ecological restoration of boreal forested ecosystems: Finland as an example. Silva Fennica vol. 36 no. 1 article id 572. https://doi.org/10.14214/sf.572

Keywords: biodiversity; ecosystem management; disturbance dynamics; monitoring; heterogeneity; nature conservation; hierarchy

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Kuuluvainen, Department of Forest Ecology, University of Helsinki, P.O.Box 27 FIN-00014, Finland E-mail: timo.kuuluvainen@helsinki.fi
Aapala, Finnish Environment Institute, Expert Services Department, Nature Division, P.O. Box 140, FIN-00251 Helsinki E-mail: ka@nn.fi
Ahlroth, University Museum, Section of Natural History, P.O. Box 35, FIN-40351, Jyväskylä, Finland E-mail: pa@nn.fi
Kuusinen, Ministry of the Environment, Land Use Department, P.O.Box 380, FIN-00131 Helsinki, Finland E-mail: mk@nn.fi
Lindholm, Finnish Environment Institute, Expert Services Department, Nature Division, P.O. Box 140, FIN-00251 Helsinki E-mail: tl@nn.fi
Sallantaus, Pirkanmaa Regional Environment Centre, P.O. Box 297, FIN-33101 Tampere, Finland E-mail: ts@nn.fi
Siitonen, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi
Tukia, Finnish Environment Institute, Expert Services Department, Nature Division, P.O. Box 140, FIN-00251 Helsinki E-mail: ht@nn.fi

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