Carabid beetle communities associated with coniferous plantations in Britain: the influence of site, ground vegetation and stand structure

Carabid beetles were sampled by pitfall trapping in 44 pine and spruce forest stands in England and Scotland using chronosequences of plots across different bioclimatic zones. The sample plots were selected on the basis of plantation age, tree species, and forest category. In each plot, a range of environmental variables were measured, some of which were used to interpret differences in carabid community composition. A total of 51 carabid species was identified; the highest individual plot total being 19 species, and the lowest two species. Correspondence analysis showed that the most significant factors affecting carabid community composition were latitude, canopy structure, soil organic matter and vegetation diversity. General linear modelling indicated that carabid species richness was negatively related to both canopy vertical structure and soil organic matter, while species diversity was negatively related to canopy vertical structure and tree species, suggesting that more species-rich, diverse carabid communities are associated with open, drier conditions. The numbers of forest specialist carabids increased with increasing plantation age, together with a corresponding decrease in non-woodland species, even for previously non-woodland sites. Consequently, longer forest rotation lengths may be expected to benefit forest carabids, particularly where stands are structurally varied with canopy gaps present.