Hedgerow structure as an indicator for multi-taxonomic biodiversity: a comparative approach between ground and airborne lidar measurements

Broadleaved hedgerows provide important refuges for forest biodiversity within intensively managed pine plantation landscapes. However, little is known on the relationships between the vertical and horizontal structure of these hedgerows and the associated taxonomic biodiversity, as well as the use of these characteristics as indirect bioindicators. LiDAR-derived metrics are increasingly used in ecology, but few studies have evaluated their ability to capture structural drivers of multi-taxonomic biodiversity compared to traditional field measurements. We investigated whether structural metrics obtained from airborne LiDAR and from ground surveys could predict multi-taxonomic biodiversity and tree-related microhabitats (TreMs) profile in 22 broadleaved hedgerows located at the edge of maritime pine plantations. Six taxonomic groups (vascular plants, butterflies, carabid beetles, spiders, birds and reptiles) and TreMs were surveyed. Eleven LiDAR- and twelve ground-based structural variables were quantified. LiDAR-derived horizontal variability in total cover (canopy + understorey vegetation) was the best predictor of overall multidiversity (R² = 0.28), whereas mean canopy cover most strongly explained the multidiversity of forest-specialist species (R² = 0.46). Both variables outperformed equivalent ground-based variables. By contrast, LiDAR metrics showed no predictive power for TreMs abundance or richness, while basal area measured in the field proved to be a good predictor (R² = 0.47 and 0.43 for TreMs abundance and richness, respectively). Our findings highlight the complementarity of LiDAR- and ground-based indicators for biodiversity assessment. As high-resolution LiDAR data become increasingly available at broad scales, horizontal heterogeneity and canopy cover emerge as promising indirect indicators of multi-taxonomic biodiversity in hedgerows across large landscapes.