Carbon content and pH as important drivers of fungal community structure in three Amazon forests

Abstract

Amazonia comprises a mosaic of ecosystems that harbor high biodiversity. Knowledge about fungal diversity and ecology in this region remains very limited. Here, we examine soil fungal communities in forests of the Colombian Amazonia and their relationship to important edaphic variables. Fungal communities were studied in terra-firme forests dominated by arbuscular mycorrhizal (AM) trees, terra-firme forests with the ectomycorrhizal (EcM) tree Pseudomonotes tropenbosii (Dipterocarpaceae), and white sand forests (WSF) with the EcM host plant genera Dicymbe and Aldina (Fabaceae). Fungal community composition was determined through 454-pyrosequencing of the ITS2 region of ribosomal DNA. We established the impact of the type of forest and edaphic parameters in structuring the fungal communities. We found a high diversity of fungi with 2,507 OTUs occurring in the soil samples studied. Carbon content and pH were the main edaphic factors contributing to structure the fungal community across all forests. Fungal community composition differs among terra-firme plots and WSF, while it was similar among AM and EcM-dominated areas in terra-firme. Our results revealed an important EcM fungal diversity in terra-firme AM-forests, where some EcM plants such as the ones in the genera Coccoloba and Neea occur scattered within an AM-matrix. This is a first approximation to understand the ecology of soil fungal communities in forests of the Colombian Amazonia. We found that fungal soil communities have a spatial variation related to forest type (terra-firme and WSF), soil pH, and soil carbon content. Due to the strong correlation between vegetation and soil fertility in Amazonia, it is difficult to understand the effects of those factors to the fungal communities.