Temporal patterns of seedling mortality by pine weevils (Hylobius abietis) after prescribed burning in northern Sweden

Abstract

Damage by the large pine weevil, Hylobius abietis (L.), is a major threat to conifer plantations throughout Eurasia, but damage is usually less severe in northern areas. However, pine weevil damage seems to increase if the sites are burnt. The aim of this study was to determine the effects of variations in the time of planting (with respect to the total age of the clear-cut and the time since burning) on pine weevil damage to seedlings on burnt sites in northern Sweden. The study also explored whether there is an optimal time for planting at which damage levels are reduced to acceptable levels. Ten sites were selected in an inland area of northern Sweden where pine weevils are normally scarce. The sites were dry–mesic and represented a range of times since clear-cutting and since burning. The sites were planted in June 1998, 1999 and 2000 with 1-year-old container-grown seedlings of Norway spruce [Picea abies (L.) Karst.]. Pine weevil damage was reduced if planting was done no earlier than 3 years after clear-cutting and no earlier than 2 years after burning. Planting too soon after burning, irrespective of the age of the clear-cut, resulted in unacceptably high damage levels.

Keywords:

• Fallow period
• forest fire
• planting
• regeneration

Acknowledgments

We are grateful to Mikael Westerlund for 6 years of laborious fieldwork collecting data for this study. We are also grateful to Gunnar Jansson for valuable discussions and help with the statistics and to Göran Nordlander for discussions on the interpretation of results. Thanks also to John Blackwell for language editing.