Insect diversity on clearcuts in boreal forest landscapes

• Intensive management and loss of natural disturbance dynamics in boreal forests leads to habitat loss and degradation for forest dwelling species. As a consequence, many species have become threatened, especially those dependent on dead wood. Integration of conservation in forest management is therefore essential for protecting boreal forest species diversity. To optimise conservation efforts, we need to understand species habitat requirements and diversity patterns in managed forests. This thesis aims to increase our understanding of insect species diversity patterns on clearcuts in boreal forest landscapes. I have surveyed beetles, bees and wasps on clearcuts in two boreal forest regions in Sweden and assessed the importance of clearcut properties and composition of surrounding landscape for species occurrence and diversity. Locally, amount of dead wood was positively associated with high species richness and individual species occurrence of certain wood-dependent beetles. Bee and wasp species richness increased with high local flower richness and clearcut size. Landscape composition was at least as important as local habitat characteristics for shaping diversity patterns. Burned forest land in surrounding landscape increased wood-dependent beetle species richness, while burning of clearcuts had only a weak effect on beetles, bees and wasps. This is probably because burned forest land on landscape scale includes higher habitat diversity with larger dead wood amounts, compared to burned clearcuts. Bee and wasp species richness increased with amount of early-successional habitats in the landscape, indicating that most species are associated with open habitats. The bee and wasp fauna differed considerably between landscapes. Therefore, conservation efforts need to be dispersed throughout the region to preserve the entire fauna. To promote insect species diversity on clearcuts in managed boreal forests, larger amount and diversity of dead wood needs to be created. Species dependent on sun-exposed dead wood or flowering plant richness can be favoured by prolonged open-habitat stage on parts of clearcuts. Concentrating certain conservation efforts to some clearcuts in the landscape is probably necessary in order to create high-quality habitats.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Skogsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Forest Science (hsv//eng)

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