Natural regeneration of the herbaceous community in a semiarid region in Northeastern Brazil.

This study aimed to describe and compare the interannual changes in the diversity and population structure of herbaceous plants in an anthropogenic area that has been regenerating for 15 years and to identify the similarities and differences in the biological attributes of the community compared with the characteristics of a regenerating conserved area. In total, 105 plots measuring 1 m(2) were established. In each plot, the herbaceous plants were identified, and their height and stem diameter were measured for two consecutive years. The herbaceous flora of the anthropogenic area was represented by 86 species in 70 genera and 27 families, and there were no significant differences in the average richness between years. The conserved area was represented by 71 species in 63 genera and 35 families, and there was a significant difference in the total richness between areas and between years, except when comparing the richness between the conserved area and the anthropogenic area during the second year. Considering both the anthropogenic and conserved areas, 123 herbaceous species were listed, and the similarity between areas was 60 %. For the anthropogenic area, the floristic similarity between years was 95 %, and in the fragment of the conserved area, the similarity was 74 %. The diversity and density were significantly different between years and between areas. Given these results, this study suggests that 15 years of natural regeneration for the caatinga is not sufficient to reestablish its native flora with respect to its herbaceous component.