Spiders, beetles and moths in exotic plantations and native woodlands: indicators of forest biodiversity at stand and landscape scales

Plantation forests constitute a large proportion of the forest estate in many countries, particularly in temperate regions of Europe. In addition, large scale deforestation has led to the fragmentation of natural forests within heavily managed agricultural landscapes. In light of this, it is important that the potential of plantations to support a diverse flora and fauna, particularly for specialised forest species, is assessed. We examined arthropod diversity in mixed and single species plantations of non-native conifers and in native woodlands in Ireland to assess the potential of plantations to support forest species. Spiders and Carabid beetles were sampled with pitfall traps and moths with light traps among forest types and measured environmental factors included stand structure, soil attributes, plant richness and forest cover. Species composition and richness differed between plantations and native woodlands, and responses differed by taxonomic group. At the stand scale invertebrates were related to litter and vegetation cover, and forest type, but variables at the landscape scale were only important for moths. These findings indicate that forest policy aimed at promotion of biodiversity in plantations should support greater diversity of stand structure and tree species composition. The planting of more species of native provenance should also be encouraged.