An initial geopedological survey and description of historic raised beds in north-western Ireland

Raised Bed (RB) field structures in northwestern Ireland are historical relics of widespread agriculture before and during the Great Famine in the mid-19th century. Their primary purpose was to improve drainage on shallow, waterlogged soils for cultivation of crops. Today, the undulating surface morphology created by the ridges and furrows remains visible in many locations, raising questions about how many of these historic fields actually still exist, whether they are mappable, and if their soils have undergone persistent anthropogenic changes. In this study, we analyse three different RB sites located in varying topographical positions and on different parent materials. High-resolution digital elevation models (DEMs) are created using UAV-based photogrammetry to analyse the surface morphology and model surface flow accumulation and wetness. Soils are analysed using trenches and surface samples taken from ridges and furrows. Our results indicate that satellite or aerial imagery alone is insufficient for reliably detecting RB sites, as the height difference between ridges and furrows is too subtle. Ridge spacing and furrow depth are best observed using high-resolution DEMs (<50 cm cell size). The modelled surface hydrology suggests that the drainage function of RB sites remains, with furrows retaining more moisture than ridges. This can have significant implications for microhabitat structures within RB fields, potentially influencing faunal species composition and abundance. Furthermore, we find significant differences in specific elemental concentrations between soils on ridges and soils on furrows, as well as differences in grain size distributions. These findings indicate a wide range of potential legacy effects present in RB fields that merit further investigation.