Fire, flooding, and herbivory: interactive drivers of taxonomic and functional diversity in a tropical wetland

Abstract Fire and flooding are key ecological filters that shape biodiversity and ecosystem functioning in tropical wetlands. This study investigates the combined effects of prescribed fire, flood regimes, and herbivory on the taxonomic and functional diversity of herbaceous communities in the Brazilian Pantanal, the world’s largest continuous floodplain. Using a long-term experimental design with 32 one-hectare plots distributed across two flood levels (according to the region’s altitude), we applied four fire treatments—Early, Modal, Late, and Control—and assessed species richness, vegetation cover, and functional traits over time. Herbivory was inferred from biomass measurements and incorporated into statistical models. Results revealed that species richness and diversity metrics were highest in low-flood areas subjected to low-intensity fires (Early and Late treatments), while high-intensity fires (Modal) reduced both taxonomic and functional diversity, particularly in highly inundated zones. Herbivory can exert a negative synergistic effect when combined with fire, leading to reduced species richness and functional divergence. Beta diversity analyses showed that species turnover was the dominant process across treatments, although nestedness contributed significantly in high-flood areas exposed to Modal fire. Functional diversity metrics indicated ecosystem resilience, with greater functional regularity and divergence observed in highly inundated areas. The findings underscore the importance of fire regime, flood intensity, and grazing pressure in structuring herbaceous communities. Prescribed fire, when applied with consideration of seasonal timing, flood level, and grazing dynamics, can serve as a strategic tool for maintaining pyrodiversity and ecosystem services in fire-dependent wetlands. However, inappropriate combinations of fire and herbivory may lead to biodiversity loss and functional homogenization, especially in flood-prone zones. These insights are critical for developing adaptive fire management strategies that balance ecological integrity with socio-economic needs in the Pantanal biome.