Comparison of invertebrate abundance and biomass between a clear-cut stand and four stands under tree cover in Swedish boreal coniferous forests

Abstract

This study assesses differences between a seven-year old clear-cut and four forest habitats as regards abundance and biomass of different invertebrate taxa - important for habitat quality for insectivorous birds. Forest types studied were pine bog, spruce mire, mesic spruce and pine heath forest. Data were collected in the second half of June 1984 (to coincide with the peak feeding demands of many nestling birds). Results indicate that the clear-cut differed more from the tree covered habitats with respect to the field layer fauna than with respect to the terricolous fauna. Compared to the forest habitats, the clear -cut was characterized by a higher abundance and biomass of sap-suckers (Hemiptera: Homoptera and Heteroptera) but a lower abundance and biomass of leaf-eating herbivorous larvae (Hymenoptera: Symphyta and Lepidoptera) in the field layer. The difference with respect to leaf-eating larvae was probably caused by low abundance of larvae food plants in the clear-cut. This may be an important ecological difference because these larvae can be an important food source for insectivorous birds.