High diversity and variability of root-associated fungi in Aucoumea klaineana, a monodominant Central African timber species.

Aucoumea klaineana is the most important timber species in Central Africa, naturally forming monodominant stands. While soil fungi are crucial for plant growth, their role in promoting monodominance or supporting suppressed, light-demanding trees remains underexplored. This study, the first to analyze the root mycobiota of A. klaineana, investigates fungal communities in monodominant stands and old-growth mixed forests in Gabon, and plantations in the DRC, sampling both canopy-reaching vs. suppressed individuals, using ITS2 rDNA and 18S rDNA high-throughput sequencing. We identified high fungal diversity in both regions but found no "core mycobiota" across stand types or tree social status (canopy-reaching vs. suppressed). Fungal communities varied significantly between stand types, emphasizing a context-dependent nature. Moreover, no distinct fungal communities characterize the mycobiota of suppressed trees. Our findings indicate that fungal associations, including mycorrhizal ones, are unlikely to be a driver of monodominance in A. klaineana. These results highlight the need to consider alternative processes, not related to fungal interactions, such as root grafting, in explaining the persistence of suppressed trees and the dynamics of monodominant stands of A. klaineana. Finally, this study illustrates the highly variable and diverse belowground communities associated with A. klaineana, whose functions and interactions could contribute to the sustainable management of this major timber tree species.