Disentangling the ecological drivers of woody plant hyperdominance in the Cerrado: A dissociation between abundance and biomass in forest and savanna formations

The hyperdominance of a few tree species is a recurrent phenomenon in tropical ecosystems, but the mechanisms determining its occurrence and intensity remain poorly understood, especially in heterogeneous biomes such as the Brazilian Cerrado. Using data from 6279 sample units from the National Forest Inventory, we investigated patterns and ecological determinants of hyperdominance in abundance (Ha) and aboveground biomass (Hb) in forest (FF) and savanna (SF) formations. We recorded 125,494 individuals belonging to 1316 native species, of which 90 (6.8%) were hyperdominant. Hyperdominance was more frequent in FF (Ha: 6.4%; Hb: 4.8%) than in SF (2.2% in both). Only 2% of species were simultaneously hyperdominant in abundance and biomass, revealing distinct ecological strategies underlying each dimension of dominance. The unimodal relationship between the richness of non-hyperdominant species and hyperdominance intensity supports the combined action of selection and niche complementarity processes, contradicting purely neutral expectations. Basal area had contrasting effects (negative on Ha but positive on Hb) reflecting the divergent role of vegetation structure in each metric. Our results indicate that hyperdominance in the Cerrado arises from the interaction between abiotic and biotic filters varying with the vegetation formation context. The dissociation between abundance and biomass demonstrates that different ecological mechanisms underpin dominance in forest and savanna formations, highlighting that the biome’s functional stability depends on the balance between dominant and rare species. These findings improve understanding of community assembly mechanisms and provide guidance for conservation and management in heterogeneous tropical ecosystems. • Only 2% of species are hyperdominant in both abundance and biomass. • Abundance and biomass dominance shaped by contrasting ecological filters. • Vegetation structure mediates the intensity of hyperdominance patterns.