The Cerrado is the largest savanna biome in the Neotropics and considered a major hotspot for world
biodiversity. However, over recent decades the area has increasingly been converted to intensive agricultural
ecosystems, primarily for soybean production. Conservation tillage systems have gained major importance in
tropical America, especially in the Brazilian Cerrado. Long-term field experiments were established to evaluate
the effects of soil tillage on soybean production in the Cerrado. The aim of our study was to determine arbuscular
mycorrhizal fungi (AMF) diversity in three natural savanna forests and compare with AMF communities
established in three field experiments focusing on soybean production. Since 2000, these experiments differed
only in the crop rotation. In one experiment, the rotation was bi-annual with soybean and maize, in the second
soybean was mono-cropped, and in the third the soybean/maize rotation was on a more intensive, annual basis.
AMF spores were extracted from the soils, counted and morphologically identified. In total, 63 AMF species,
belonging to 20 genera, were detected. Average spore densities and species richness decreased in conventionally
tilled systems (3–4 spores g−1 and 12–17 species), when compared to no-tillage (4–6 spores g−1 and 15–18
species) and natural savanna (9–11 spores g−1 and 16–22 species), but AMF evenness (Pielou index) was higher
under both tillage systems (0.65–0.77), than in the savanna forests (0.54–0.62). AMF community composition
significantly differed between all systems. Indicator species were revealed for all three ecosystems: e.g. Glomus
macrocarpum and Sclerocystis sinuosa (Cerrado), Sc. coremioides (no-tillage) and Gigaspora margarita, Racocetra
coralloidea and Ra. fulgida (tillage). In conclusion, soil cultivation and fertilizer application lead to decreased
AMF species richness but remarkably AMF diversity was maintained on similarly high levels in soybean-based
crop production systems, even under intensive soybean mono-cropping. The changes in AMF community
structure rather were linked to soil pH and potassium, calcium and magnesium than to phosphorus availability
or the organic carbon contents. Several species were unrecoverable from either of the tillage systems following
conversion from natural savanna forests to cropland.