Bringing Fire Back: How Prescribed Fires Shape Ant Communities in a Fire-Suppressed Neotropical Savanna

We evaluated the effects of different fire regimes on the ground-ant community from a savanna (Cerrado) reserve in southern Brazil, where a process of woody encroachment has been taking place. Ants are a dominant faunal group in tropical savannas. Over ~8 years, experimental plots were protected from fire or burned every one or two years. An additional treatment (adaptive) included annual fires and a reduction in woody biomass to increase fuel loads. Ants were collected prior to the first prescribed fire and again four times. We expected that fire would increase the diversity and overall abundance of open-savanna ant specialists, depending on the extent of changes in vegetation structure. Changes in litter depth, grass cover and bare ground in burned plots were most evident 88 months after the first fire and did not differ between fire regimes. Similarly, overall ant species richness and occurrence neither differed between fire treatments nor from the control. However, burned plots showed a significant increase in the richness and occurrence of open savanna specialists, and a decrease in species most typical of dense savanna or dry forests. As ant responses did not differ between the annual, biennial, and adaptive treatments, we suggest that a fire return interval of two years is enough for reverting the loss of open savanna ant specialists in areas that have been protected from fire for decades.