Hannu Saarenmaa. (1978). The occurrence of bark beetles (Col., Scolytidae) in a dead spruce stand flooded by beavers (Castor canadensis Kuhl.) . Silva Fennica vol. 12 no. 3 article id 5003. https://doi.org/10.14214/sf.a14857

Original keywords: kuusi; hyönteistuhot; tulva-alueet; kaarnakuoriaiset; kanadanmajava

English keywords: bark beetles; Norway spruce; Picea abies; Castor canadensis; insect damages; Trypodendron lineatum; flooded areas; Pityogenes chalcographus; Hylurgops palliatus; Ips typographus; Dryocetes autographus

Abstract | View details | Full text in PDF | Author Info

The aim of the study was to determine which kinds of insects had infected the Norway spruce (Picea abies (L.) H. Karst.) in different stands killed by flooding caused by beavers (Castor canadensis Kuhl), and if there was any danger that they would subsequently cause damage in the surrounding forests. The effect of tree diameter and certain stand characteristics on the fauna of dead trees are discussed. The occurrence of different insect combinations and qualifications for their coexistence were studied.

Pityogenes chalcographus L., Trypodendron lineatum O., Hylurgops palliatus Gyll. and Dryocetes autographus Ratz. occurred most abundantly. 20 phloem or wood boring species were observed in 5 regular succession types. Secondary species occurred in a virgin stand while Ips typographus L. was found at the edge of a felling area. Owing to the flooding, species preferring moist conditions were abundant. In this case damages had not spread to the surrounding forests which, however, might be possible under certain conditions.

The PDF includes a summary in English.

Saarenmaa, E-mail: hs@mm.unknown

Category : Research article

article id 648, category Research article

Sauli Härkönen. (1999). Forest damage caused by the Canadian beaver (Castor canadensis) in South Savo, Finland. Silva Fennica vol. 33 no. 4 article id 648. https://doi.org/10.14214/sf.648

Keywords: Canadian beaver; Castor canadensis; forest damage; prevention of damage; type of damage

Abstract | View details | Full text in PDF | Author Info

The increasing Canadian beaver (Castor canadensis) population has caused forest damage in Finland. However, the occurrence, extent and importance of the damage have not been comprehensively studied. The field inspection was carried out in all of the beaver damage areas (n = 50) in the Anttola, Juva and Pieksämäki game management units in summer 1998. The characteristics of the damage areas, types of damage and the severity of the damage were examined. The size of the damage areas averaged 2.2 ha. The damage areas occurred on peatland forest more (p < 0.05) than expected. The dominant tree species were commercially valuable trees such as Scots pine (Pinus sylvestris) (33%), Norway spruce (Picea abies) (18%) and birches (Betula spp.) (47%). Birch occurred as dominant tree species more (p < 0.05) than expected. The proportion of older forest development classes was considerable. The most important type of damage was flooding (50%) caused by the damming activity of beavers. The trees were dead or dying in 18% of the damage areas. It was estimated that the ecosystem engineering performed by beavers was of no importance in 28% of the damage areas. Prevention of beaver damage has been carried out in 80% of the damage areas. In the study area, beaver numbers have steadily increased, although the number of beavers taken by hunting and the allowed hunting harvest have sharply increased. It is suggested that the methods used to prevent beaver damage should be improved and a compensation system should be provided by the state for the most damaged areas. Beavers can cause damage to commercial forestry, and this should be taken into account more effectively in the management plans made by the game management districts.

Härkönen, South Savo Game Management District, P.O. Box 14, FIN-51901 Juva, Finland E-mail: sauli.harkonen@riistanhoitopiirico.inet.fi

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