Spider species and assemblages in forest plantations of various ages

We describe the spider communities collected by pitfall traps from forestry plantations at 16 areas across the UK, primarily planted with conifers, as part of the Biodiversity in Britain's Planted Forests research programme. The large collection of 13,863 identifiable individuals contained 191 species, mainly ones known to be associated with woodlands. The biggest source of variation in the data was a geographical gradient from the southeast to the northwest of the British Isles, presumably reflecting climatic conditions. The far northwestern sites held a relatively homogeneous assemblage typified by Micrargus apertus, while the southeastern sites held a more diverse mix of species. There was some evidence for tree species affecting the assemblage, with differences between the spiders of Sitka spruce and Norway spruce, also between Corsican pine and Scots pine. The age of forest was also influential, with highest diversity in the youngest stands. Overall, we suggest that these artificial plantations contribute to a surprising degree to our forest invertebrate biodiversity and merit further studies to elucidate the factors driving species assemblages within plantations of different tree species and of different ages.