Fire drives abandoned pastures to a savanna-like state in the Brazilian Atlantic Forest

Most tropical forests are threatened by a myriad of human-induced disturbances, associated with land use changes, altered fire regimes and direct deforestation. The combined effect of multiple disturbances can shift forests towards a new, resilient state that is qualitatively distinct in structure, species composition and function. We found that abandoned pastures affected by fires in the Brazilian Atlantic forest showed similarity in terms of vegetation structure and plant functional traits to a savanna-like ecosystem. Burned communities exhibited more C4 grass cover, higher proportion of resprouts and lower canopy cover as compared to the old-growth forest. Moreover, 79% of woody species at the burned sites are generalists with a widespread distribution, which includes the cerrado (Brazilian savanna). Woody species composition was strikingly different from old-growth forests, since burned sites were dominated by Moquiniastrum polymorphum (Less.) G. Sancho (Asteraceae), a fire-resistant species with a ruderal behavior that was absent in the old-growth forests. The results observed in this study provide biological evidence for an arrested succession with the establishment of a savanna-like ecosystem as an alternative stable state. These findings reinforce the notion that the establishment of an alternative stable state (e.g., savanna-like state) hypothesis for the Brazilian Atlantic Forest should be considered, especially under the current climate change scenarios.