The influence exerted by tree communities, topography and soil chemistry on the assembly of macrofungal communities remains poorly understood, especially in highly diverse tropical forests. Here, we used a large dataset that combines inventories of macrofungal Basidiomycetes fruiting bodies, tree species composition and measurements for 16 soil physico-chemical parameters, collected in 34 plots located in four sites of lowland rainforests in French Guiana. Plots were established on three different topographical conditions: hilltop, slope and seasonally flooded soils. We found hyperdiverse Basidiomycetes communities, mainly comprising members of Agaricales and Polyporales. Phosphorus, clay contents and base saturation in soils strongly varied across plots and shaped the richness and composition of tree communities. The latter composition explained 23% of the variation in the composition of macrofungal communities, probably through high heterogeneity of the litter chemistry and selective effects of biotic interactions. The high local heterogeneity of habitats influenced the distribution of both macrofungi and trees, as a result of diversed local soil hydromorphic conditions associated to contrasting soil chemistry. This first regional study across habitats of French Guiana forests revealed new niches for macrofungi, such as ectomycorrhizal ones, and illustrate how macrofungi inventories are still paramount to can be to understand the processes at work in the tropics.

34 forest plots in French Guiana were sampled to inventory trees floristic composition and Basidiomycetes diversit, together with soil physico-chemical characteristics. Estimates of diversity (indices of richness, shannon and simpson) of tree and fungel communities were calculated. The relative contribution of tree diversity and floristic composition, and soil nutrients and topography were determined