Grazing effects on soil compaction in mediterranean oak woodlands

Abstract This study evaluates the impact of grazing on soil compaction in two Mediterranean oak woodlands ( Quercus rotundifolia Q and Quercus pyrenaica Qp ) in the Montesinho Natural Park in north-eastern Portugal. In each habitat, paired fenced plots (grazed versus ungrazed) were monitored. Soil samples were collected at depths of 0–10 cm and 10–30 cm in order to assess texture, bulk density, moisture content and penetration resistance. The Qr plot was grazed by goats at a moderate intensity for 15 consecutive days. Meanwhile, the Qp plot was grazed by sheep at a higher intensity for 55 intermittent days over an extended period. Soil resistance was measured using an impact penetrometer and analysed using two-way ANOVA—SS Type III, principal component analysis (PCA) and Pearson correlations. Grazing significantly increased soil compaction in the Qr plots (3.03 ± 0.23 vs. 1.87 ± 0.1 Mpa), but not in the Qp plots (2.03 ± 0.2 vs. 1.70 ± 0.1 Mpa). Penetration resistance was positively correlated with clay content and bulk density, and negatively with silt content and moisture content. This study, conducted in Mediterranean mountain forests with Q. pyrenaica established on Umbric Leptosols and Q. rotundifolia on stony Leptosols derived from basic rocks, demonstrates that the effects of grazing on soil compaction are more closely linked to the intrinsic properties of the soil than to grazing stocking rate itself. These findings demonstrate that pre-existing soil properties modulate the effects of grazing on soil compaction, underscoring the importance of site-specific conditions in the sustainable management of Mediterranean silvopastoral systems.