The Importance of Young Plantation Forest Habitat and Forest Road-Verges for Ground-dwelling Spider Diversity

The potential of forest roads to enhance habitat diversity within plantation forests is an important conservation issue. If properly managed, these open spaces allow structurally diverse vegetation to grow at the road-verges, which may support greater invertebrate abundance and species richness, increasing overall forest biodiversity. We investigated spider diversity along road edges in young plantation forests in Ireland, the influence of road-verge vegetation and the consequences of doubling the standard forest road-width currently used in Ireland. Active ground-dwelling spiders were studied in eight Sitka spruce (Picea sitchensis) plantations using pitfall trapping one year after planting and five years after planting. A total of 16,741 spiders were caught, from which 141 species were identified from 14 families. Ten spider species of conservation importance were found in the road-verges demonstrating their importance as habitats for spider diversity. We found no difference in ground-dwelling spider diversity between road-verge and forest interior plots at this stage in the rotation. We found no advantage or disadvantage of increasing the road-width of forest roads for ground-dwelling spider diversity of young plantation forests. The findings of this study are discussed in the context of the management of plantation forests for biodiversity conservation and associated forest policy development.