Effect of grazing on carbon sequestration and tree growth that is developed in a silvopastoral system under wild cherry (Prunus avium L.)

- Silvopasture promotes more C sequestration in soil surface than silvoarable practices.
- C sequestration in upper soil layers depends on soil biological activity.
- C sequestration in deeper soil layers depends on soil physical properties.
- Root growth modifies soil density and sand proportion, affecting C sequestration.

Silvopastoral systems have been considered a good tool for carbon sequestration by taking up atmospheric carbon dioxide and storing it in the soil. The effect of animal presence on carbon sequestration in this type of agroforestry system has been studied recently. However, the soil carbon storage in these systems is influenced by the stocking rate. In addition, soil fractions have been known to influence carbon storage. This study was undertaken in order to examine the effects of livestock grazing at two different stocking rates [Light Stocking Rate (LS; 4 sheep ha− 1) and Heavy Stocking Rate (HS; 8 sheep ha− 1)]. This was compared with the soil chemical and physical properties of No Grazing (NG) pastures, the amount of C stored in the whole soil, in three different soil fractions (250-2000, 53-250, and < 53 μm), at each of four soil depths (0-25, 25-50, 50-75, and 75-100 cm), and the tree growth in a silvopastoral system under Prunus avium L. The presence of animals in silvopastoral systems plays an important role in carbon sequestration by the direct or indirect modifications of the pH, the soil bulk density, and the soil fraction proportions. The LS treatment promoted carbon sequestration linked to macroaggregates in the upper soil layers when compared with the HS treatment and the NG treatment. However, in deep horizons, the NG treatment enhanced the soil organic carbon storage more than did the grazing treatments and this carbon was linked to microaggregates, increasing the soil density. A better carbon concentration was found when 1 m of soil depth was evaluated in an LS treatment, but no differences were apparent in the carbon storage per hectare that were found due to a high soil bulk density in an NG treatment.