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Before modern forestry started, forest fire was the dominating large-scale disturbance in boreal forest. Prescribed burning of clear-cuts is increasingly used as a conservation measure but is potentially less beneficial for fire-associated species than burning of intact forest. We investigated the temporal effect of prescribed burning of clear-cuts in two regions in central Sweden: one region with a relatively unbroken forestfire continuity (Orsa) and one region with a broken fire continuity (Långshyttan) more typical for Fennoscandia. The dead wood associated (saproxylic) beetle fauna was sampled with ten trunk-window traps in each of 16 clear-cuts. We used a paired design with two clear-cuts that had been logged at the same time and where one had been subjected to prescribed burning one or two years after clear-felling. We sampled clearcuts either the same year as burning (0-year old) or 1-, 2- or 4-years post-burning. In Orsa we sampled five pairs (0-4 years old) and in Långshyttan three pairs (0-2 years old). We caught 147 species (5908 individuals) of saproxylic beetles and 33 of those species were fire-associated. There was a pronounced temporal effect of prescribed burning on beetle abundance and species richness. The year of the fire there was a higher abundance and species richness in the burnt clear-cuts than in the unburnt clear-cuts. This positive effect disappeared already after one year. This pattern remained when we restricted our analysis to only fire-associated species. There were several regional differences consistent with a better fire continuity in Orsa: (1) In four out of five clear-cut pairs in Orsa there was a positive effect of burning on abundance and species richness of fire-associated species. In Långshyttan there was no such effect. (2) In Orsa the species composition of the fire-associated species differed between burnt and unburnt clear-cuts in four out of five pairs. In Långshyttan there was a difference only in one out of three pairs and that difference was smaller than the differences in Orsa. (3) When we restricted our analysis to 0- to 2-year old clear-cuts in order to have identical sample sizes in both regions, we found 725 individuals of 25 species of fire-associated species in Orsa and 218 individuals of 24 species in Långshyttan. (4) The four fire-dependent species that we found were the most specialised species and three of these, Melanophila acuminata, Sphaeriestes stockmanni, and Acmaeops septentrionis were only found in Orsa whereas Henoticus serratus was found in both regions. To conclude, prescribed burning of clear-cuts only had a short-lived positive effect on saproxylic beetle diversity. This result casts doubt on the value of using prescribed burning of clear-cuts as a conservation measure. The better effect of prescribed burning in Orsa than in Långshyttan points to a differential effect of the value of prescribed burning. It also indicates that a long period of restoration burning might be needed in many parts of Sweden in order to increase the populations of fire-associated species.

Publicerad i

Titel: Beetles: Biodiversity, Ecology and Role in the Environment
Utgivare: Nova Science Publishers

SLU författare

UKÄ forskningsämne

Ekologi
Skogsvetenskap

Publikationens identifierare

  • ISBN: 978-1-63463-380-2

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/64399