The mycorrhizae of a tropical savanna growing in oligotrophic and stony soils were compared with those of a disturbed area that had been reclaimed with introduced species and of an area that was disturbed but not revegetated. All were compared with natural regeneration in a savanna that had been disturbed 12 years previously. Arbuscular mycorrhizae (AM) were common in savannas. Cyperaceae species, which were codominant with Graminaea, showed high levels of infection frequency (45%) like the Gramineae (61%). Arbuscules observed in the Cyperaceae indicated functionality. There were few plants in disturbed, nonrevegetated sites, but those present had AM. Observations of roots from soil monoliths showed that AM were present in disturbed areas, but compared with natural, succesional and revegetated savanna had a lower infection frequency (48-59% vs 75%), lower intensity (10-15% vs 25%) and a lower percentage of arbuscules (0.7-0.8% vs 2.3%). The percentage of vesicles was also lower in succesional savanna than in natural savanna (1.6% vs 4.8%). The revegetated site had the highest percentage of vesicles (6.6%). Although a high frequency of mycorrhizal infection has been reestablished in disturbed areas, the intensity and structure of the infection suggests that mycorrhizal function has not been restored to the original levels. We hypothesize that neither plants nor fungi have adapted to the new edaphic conditions.
