Beech understoreys in pine forests as places that partly favour the functioning of forest assemblages of ground beetles (Col. Carabidae) in coniferous forest habitats

Abstract

This study investigates the effect of the enrichment of Scots pine stands with a common beech understorey on changes in the species composition and selected life traits of an important zooindicator group, such as the ground beetles (Col. Carabidae). The field investigations were carried out in a fresh coniferous forest in the Myszyniec Forest District (N Poland) in stands with (P+) and without (P) beech in the understorey. Each treatment was repeated four times. In each repetition, six pitfalls were installed. The traps were replaced 13 times, every two weeks, from April to October. In total, 4412 specimens classified into 25 species of ground beetles were captured. The tree stands with the beech understorey were observed to contain a significantly higher number of species than the ones with the beech undergrowth. Also, the value of the Shannon index of species diversity (H’) and mean individual biomass (MIB) were significantly higher in the treatment with the beech understorey. Principal Component Analysis showed variations in Carabidae assemblages within the analysed types of forest. Pterostichus oblongopunctatus, Pterostichus aethiops and Pterostichus vernalis were more strongly correlated with the stands without beech understorey. The stands enriched with the beech understorey correlated with the occurrence of large zoophages: Carabus arvensis and Cychrus caraboides, and hemizoophages of the genus Amara. An in−depth ecological characterisation of the captured Carabidae showed that the dominant ground beetles in the investigated forest habitats, in terms of the number of caught individuals and species, belonged to forest zoophagous carabids characterised by moderate requirements for moisture in a habitat, and having the spring type of development. Representatives of large zoophages and species with the autumn type of development, i.e. species associated with later ecological succession stages, were more numerously caught in the pine stands without the beech understorey The study provides evidence that justifies the planting of deciduous undergowth in monoculture coniferous pine tree forests. The presence of an understorey contributes to higher: richness of Carabidae species, values of the MIB and abundance of large forest species presenting the autumn type of development, that is the species, which are characteristic for forest areas representing a highly advanced succession stage