The silvopastoral systems are a viable option to avoid degradation of pastures due to their potential to control erosion and the ability of some tree species to add nitrogen and other nutrients to the pasture, improving soil fertility. However, an important aspect in these systems refers to the competition for light between the tree/shrub and herbaceous components. Tiller production and the consequent density of inflorescences, directly related to seed production and, therefore, to natural reseeding, are some of the important variables for the sustainability of pastures that are influenced by the intensity of solar radiation that reaches the understory. Thus exposed and in view of the great potential of silvopastoral systems, in-depth evaluations of the aspects related to the persistence of grass components in the system are urgent, via natural reseeding and tillering. The project was carried out in an established silvopastoral system in which the trees (Eucalyptus + leguminous species) were arranged in strips consisting of four tree lines established in the pasture level ( Brachiaria decumbens) - tree strips (shade) 10 m wide interspersed with pasture tracks (sun) with 30 m - and had the following objectives: (a) to verify the effect of the shade of the trees on the seed production (quantity and quality: germinative power and vigor) and (b) to evaluate the establishment of seedlings and tillering in the system. The inflorescence density, the amount of seeds produced and the number of established seedlings were measured, in addition to studying the dynamics of grass tillering. The seeds collected in the two treatments (sun and shade) were evaluated in the laboratory for vigor and germination. The results allowed to know the influence of the shade provided by the trees on the tillering and the production of new grass plants from the germination of their own seeds, an important aspect for the persistence of pasture and for the sustainable development of silvopastoral systems. Shading negatively affected tiller density, although the lower tiller onset rate in the shade appears to have been offset by its lower mortality rate in this condition; the natural restocking of B. decumbens via self-reseeding in the evaluated silvopastoral system was not affected by the shade of the trees; shading negatively affected seed production, with changes in the management of shaded pastures being recommended through periodic deferral aiming at maintaining the soil seed bank; the shading did not affect the physiological quality (germination power) of the seeds, not compromising the sexual self-perpetuation of
B. decumbens in the silvopastoral system.