Richness of arbuscular mycorrhizal fungi (Glomeromycota) along a vegetation gradient of Brazilian Cerrado: responses to seasonality, soil types, and plant communities

The Brazilian Cerrado is a biodiversity hotspot characterized by a mosaic of phytophysiognomies and soil types. Arbuscular mycorrhizal fungi (AMF) are important components of biodiversity, participating in symbiotic relationships with plants and involved in ecosystem functioning. Variations in the AMF communities in Cerrado phytophysiognomies are not well understood. We collected soil samples in the dry, transition (dry to rainy), and rainy seasons to evaluate relationships between the AMF community, vegetation, and soil physicochemical parameters of three Cerrado phytophysiognomies that constitute a structural gradient (campo sujo: grassland, cerrado tipico: savanna, and cerradao: forest) across seasons. The floristic similarity was high between cerrado grassland and savanna, but lower between cerrado forest and grassland and between cerrado forest and savanna. Twenty-six AMF species were identified, with genera Glomus and Acaulospora common to all phytophysiognomies. AMF communities showed low similarity between different phytophysiognomies. Spore density differed between the phytophysiognomies, increasing from grassland to cerrado forest. Seasonal distribution of precipitation affected the AMF community in cerrado savanna and forest, but not in grassland soil. Differences in edaphic factors were important drivers of AMF spore density that correlated positively with soil parameters. Except for woody plant biomass, which correlated positively with spore density in the dry and transition/rainy season, no vegetation parameters showed significant correlations with spore density in any season. Despite the high floristic similarity between cerrado grassland and savanna, similarity between AMF communities is low, highlighting the importance of the vegetation gradient and its conservation in the structuring of these fungal communities.