Amazon basin pasture soils reveal susceptibility to phytopathogens and lower fungal community dissimilarity than forest

Abstract The advance of livestock towards the hydrographic basin of Mutum-Parana River, in the state of Rondonia contributes to the conversion of the amazon forest to pasture. This process can decrease the plant diversity, contributing to loss of endemic microorganisms and natural enemies leading to the replacement of native biota by non-native and generalist species. Thereby, we hypothesized that this conversion changes fungal composition, reduce fungal alpha diversity and community dissimilarity and increase the incidence of potential phytopathogenic genera at pasture soils compared to forest. Soil of 10 sampling points from forest and 10 from pasture were collected at the Mutum-Parana River basin. Via ITS amplicon sequencing of the total soil DNA, differences in composition and in the taxonomic diversity between the two environments were addressed. The phylum Ascomycota predominated in both forest and pasture. Basidiomycota presented lower percent in both, but was higher in pastures. Zygomycota and Glomeromycota presented opposite tendencies, the first being predominately present in forest and the second only present in pasture with low incidence. The fungal diversity was higher in pasture soils, contrasting our hypothesis. There were also significant correlations between soil physicochemical properties and fungal community. The reduction of the dissimilarity in pasture was confirmed and this signalized for a biotic homogenization. In addition, higher incidence of potential phytopathogenic fungi was observed in pasture. These results contribute to a better understanding of how fungal communities are driven by forest-to-pasture conversion.