Tree distance and grazing intensity shape soil properties and nutrient cycling in Mediterranean silvopastoral systems

Silvopastoral systems offer a sustainable alternative for enhancing soil fertility and nutrient cycling in pasturelands. Understanding how tree presence and grazing intensity interact spatially to influence soil properties is essential for optimizing the management of these systems. We assessed the influence of tree distance and grazing intensity on soil properties in a Mediterranean Dehesa. Soil samples (0–10 and 10–20 cm) were collected from two grazing managements—Low and Medium Intensity Grazing Management (Low-IGM and Med-IGM)—at three distances to tree trunk (0.5R, R, and 2.5R) based on canopy radius (R). Soil chemical and physical properties, potential enzymatic activity index, and stable isotopes of carbon (C) and nitrogen (N) were analyzed. Soil C, phosphorus (P), and potential enzymatic activity index peaked under tree canopies (0.5R), indicating that trees create localized fertility hotspots. Higher δ 15 N and lower C:N ratios at 0.5R suggest N enrichment from livestock excretion. Med-IGM treatment increased soil C, N, and δ 13 C compared to Low-IGM, particularly beneath trees, highlighting the interacting effect of grazing intensity and tree proximity on soil C and N dynamics. Elevated N and reduced C:N in Med-IGM indicate a possible decoupling of C and N cycles, with suggests greater risk of N losses. No effect of grazing intensity on soil physical properties was observed, indicating that grazing pressure in Med-IGM was not excessive. Our findings reveal complex interactions shaping C and N cycling in Dehesa systems and suggest that reducing grazing days and increasing tree density could help mitigate potential environmental impacts.