Contrasting Spatial Patterns of Pear Roots and Soil Biological Indicators in Intensive ‘Abbé Fétel’ Orchards: A Multi-Farm Survey

Understanding the spatial relationship between crop roots and soil biological functioning is essential for improving orchard management. This study investigated the spatial distribution of pear roots and selected soil biological indicators in five intensive ‘Abbé Fétel’ pear orchards in Emilia-Romagna, Italy, representing eight orchard–rootstock combinations. Soil cores were collected from along-row and inter-row positions at two depths (0–20 and 20–40 cm). Root length density (RLD), soil organic matter (SOM), microbial biomass carbon (MBC), soil basal respiration (SBR), and the activities of alkaline phosphatase (ALP), β-glucosidase (BGLU), and N-acetyl-β-D-glucosaminidase (NAG) were determined. Linear mixed-effects models showed that RLD was significantly higher along the tree row and in the upper soil layer. At 0–20 cm, mean RLD was approximately twofold higher along-row than in the inter-row (0.324 vs. 0.133 cm g−1), indicating that pear roots were concentrated within the shallow along-row soil. Soil depth was the main factor influencing all biological indicators. SOM was higher along-row, whereas MBC varied mainly with depth. In contrast, BGLU and NAG activities were higher in the grass-covered inter-row despite lower pear-root density, while SBR showed the highest values in the shallow along-row soil. These findings demonstrate that soil biological indicators do not necessarily mirror crop-root distribution. Instead, belowground functioning in intensive pear orchards reflects the combined influence of crop roots and inter-row vegetation, highlighting the ecological importance of both orchard compartments when assessing soil functioning.