The role of broadleaved hedgerows and landscape composition for biodiversity conservation in a pine plantation context

In forested landscapes, compositional and configurational heterogeneity have been shown to enhance biodiversity. However, changing the type of land cover to improve landscape heterogeneity remains a logistical challenge for forest managers. While hedgerows and forest patches have been widely studied for their role in promoting biodiversity in agricultural landscapes (i.e., “bocage”), it remains unclear to what extent increasing the share of these interstitial elements would enhance the diversity of different taxonomic groups in plantation landscapes. To address this question, we conducted our study in a homogeneous and monospecific pine plantation landscape in southwestern France, where we compared the diversity of six taxonomic groups in broadleaved hedgerows vs pine stand edges. We also analysed the effect of the connectivity of hedgerows to broadleaved stands and the proportion of broadleaved stands in the landscapes. Beyond species richness and community composition of each taxon, we calculated multidiversity indexes across all groups (using dominant, rare, or forest specialist species). Multidiversity was significantly higher in hedgerows than in pine stand edges. Hedgerows were home to communities with a distinct composition, including a greater abundance of rare species and forest specialist species. Increasing broadleaved cover in the landscape had a negative effect on multidiversity but altered community composition in three out of six groups. The connectivity of hedgerows to broadleaved stands had no significant effect on biodiversity. Preserving or planting broadleaved hedgerows therefore emerges as an effective and practical management method for enhancing biodiversity, particularly of forest specialist species, in pine plantation landscapes.