Natural regeneration of the vegetation of an abandoned agricultural field in a semi-arid region: a focus on seed bank and above-ground vegetation

Forest age has been reported to be a determining factor affecting species richness and composition or population abundance in forests and soil seed banks in fragmented landscapes. In this study, we characterized species richness, density, and floristic composition of the above-ground vegetation and the seed bank in young and mature forest fragments in a semi-arid region of north-eastern Brazil. Forty plots were set up in the mature forest and 40 in the young forest. Herbaceous species and seedlings and juveniles of woody species up to 1 m in height were included in the sampling of above-ground vegetation. Seed bank samples including leaf litter were collected and maintained in a greenhouse for 6 months. Our findings indicated a similarity in species richness between seed bank and above-ground vegetation. The floristic composition of the seed bank was similar from that of the above-ground vegetation throughout succession. The mean density of the seed bank was higher than that of the above-ground vegetation in both forests. Therefore, only a subset of the seeds stored in the soil seemed to consistently contribute to the natural regeneration of forests.