The aim of this work was to evaluate arbuscular mycorrhizal (AM) fungi as soil indicators and the mycor-rhization of native and exotic tree species planted in the Aca-raú basin, a transition area from the coast to the Brazilian semiarid region. Plots with 6-year-old trees of four native and three non-native species as well as one non-forested area were evaluated in terms of the diversity of AM fungi in the mycorrhizosphere and the root colonization by AM and ectomycorrhizal (EcM) fungi. Twenty-four AM fungi were identified; Claroideoglomus etunicatum, Glomus sin-uosum, Paraglomus albidum, Acaulospora laevis, and Acau-lospora brasiliensis were abundant in the forest soil. Diver-sity, dominance, evenness and richness indices of AM fungi were higher in plots with native trees. All root samples were colonized by AM fungi and only Anadenanthera colubrina, Acacia mangium, Casuarina equisetifolia and Eucalyptus urophylla formed associations with EcM fungi. Acaulospora morphotypes served as soil indicators for coverings with the native species Astronium fraxinifolium and Colubrina glan-dulosa. Exotic species may favor the proliferation of rarer AM fungi. These fungi–plant relationships may be important in the management of forest systems, and the evidence with mycorrhizal associations allows the inclusion of Brazilian species in tropical reforestation.