Contrasting community compensatory trends in alternative successional pathways in central Amazonia

Based on eight years of annual censuses in secondary forests in central Amazonia, we compared successional dynamics in areas presenting alternative states due to different land use histories. Sites that had been clearcut without subsequent use are dominated by the pioneer genus Cecropia, but their understory is characterized by a diverse species assemblage. In contrast, areas clearcut and then used for pasture are dominated by the genus Vismia, forming nearly monogeneric stands. We evaluated whether such patterns were the outcome of differences in community compensatory trends, leading to a dynamic system of sequential replacement of species in Cecropia stands, and to a persistent stage of succession in Vismia stands. Floristic turnover in Cecropia stands showed strong and consistent negative frequency dependence. In contrast, Vismia stands exhibited little or no frequency dependence, likely due to local competitive interactions or priority effects. In these stands, species of the genera Vismia and Bellucia remained dominant throughout the monitoring period, whereas species initially of low abundance and frequency remained so. Differences in recruitment were the major driver of these alternative states. As species colonization proceeds, we expect dominance in the Vismia stands to diminish, albeit slowly. Our approach proved to be a useful tool for comparing species turnover in systems presenting alternative states.