AUTHOR=De Souza Julio Henrique Germano , Difante Gelson dos Santos , Francé Otávio , Mosquera-Losada Maria Rosa , Castro Marina 
  
TITLE=Distribution of soil carbon and nitrogen in Mediterranean oak silvopastoral systems under grazing
  
JOURNAL=Pastoralism: Research, Policy and Practice
  
VOLUME=Volume 16 - 2026
  
YEAR=2026
  
URL=https://www.frontierspartnerships.org/journals/pastoralism-research-policy-and-practice/articles/10.3389/past.2026.16765
  
DOI=10.3389/past.2026.16765
  
ISSN=2041-7136
  
ABSTRACT=Soil organic carbon (SOC) plays a key role in climate regulation and the functioning of ecosystems. However, the impact of grazing on its distribution in Mediterranean oak silvopastoral soils is not well understood. This study analysed the effects of grazing on soil carbon and nitrogen dynamics in two oak-based silvopastoral systems in northeastern Portugal, namely Quercus pyrenaica and Quercus rotundifolia. Soil samples were collected at depths of 0–10 cm and 10–30 cm before and after grazing cycles. The concentrations of carbon and nitrogen in total soil and in three particle-size fractions (sand, silt, and clay) were quantified following physical fractionation. Multivariate analysis (PCA) and generalized linear mixed models (GLMM) were used to evaluate the effects of stand-forming tree species, presence of grazing, and soil depth. Soil carbon and nitrogen were significantly influenced by stand-type and soil depth, whereas grazing had no significant effect. Higher SOC values were observed under Q. pyrenaica, reaching 35.00 (±2.07 SE) g kg−1 in the 0–10 cm layer, compared with 24.6 g kg−1 under Q. rotundifolia. Carbon stocks ranged from 30.42 ± 2.12 Mg ha−1 under Q. pyrenaica to 13.25 ± 2.15 Mg ha−1 under Q. rotundifolia across the soil profile. A similar pattern was observed for soil nitrogen, with total N values reaching up to 2.28 ± 0.17 g kg−1 under Q. pyrenaica, compared to approximately 0.52 ± 0.05 g kg−1 under Q. rotundifolia. Most of the soil carbon and nitrogen was associated with the sand fraction. These results suggest that the dynamics of soil carbon and nitrogen in Mediterranean silvopastoral systems are primarily driven by vegetation type and soil depth, whereas grazing under extensive management conditions has a limited influence on SOC stocks and their distribution among soil fractions.