Post-fire succession in high-altitude grasslands: Insights from a threatened montane area in the Atlantic Forest of southeastern Brazil

High-altitude grasslands possess significant biological and hydrogeological value, yet they face ongoing biodiversity loss due to anthropogenic pressures. Despite the recurring occurrence of human-induced fires, studies on their effects on plant communities in these ecosystems remain scarce. This study aimed to understand successional processes of plant species in two high-altitude grassland areas following fire events. We tested two hypotheses: (ⅰ) species richness initially increases after fire, followed by a decline and eventual stabilization; and (ⅱ) post-fire species composition changes over time, influenced by species' life forms and developmental strategies. To evaluate post-fire effects on species richness over time, we applied Generalized Linear Mixed Models and Quadratic Models to assess stabilization patterns. Changes in plant species composition across post-fire time and transects were analyzed using Permutational Analysis of Variance (PERMANOVA) with pairwise comparisons in R software. Results showed that species richness progressively increased in both study areas, followed by a trend toward stabilization. Species composition changed significantly over time, influenced by transect location and its interaction with post-fire age, suggesting the role of microhabitat heterogeneity. The underlying mechanism of compositional change was species turnover. Asteraceae and Poaceae were the dominant families, with hemicryptophytes and chamaephytes being the most prevalent life forms. Biological traits of certain species facilitated post-fire survival and rapid regrowth. This study provides the first assessment of anthropogenic fire effects on high-altitude grasslands in Poços de Caldas, Minas Gerais, Brazil. Our findings underscore the need for further research on fire ecology in these priority conservation areas to support informed management strategies.