Increased CO sub(2) emission and organic matter decomposition by leaf-cutting ant nests in a coastal environment

Leaf-cutting ants perform a vital role in the cycling of carbon and nutrients in tropical ecosystems. Nests have high levels of organic matter and refuse dumps host up to two times more soil micro-organisms than non-nest soil. The increased levels of organic matter in the soil of nests, however, can affect CO sub(2) emissions from soil and alter the balance of atmospheric CO sub(2). We aimed at assessing the effect of nests of the leaf-cutting ant Acromyrmex balzani on CO sub(2) emissions in a coastal area of Northeast Brazil. Results show that A. balzani nests emitted up to four times more CO sub(2) than the surrounding soil and emissions were positively correlated with soil moisture and soil organic matter (SOM) content. In addition, field experiments demonstrated that refuse material has a lower residence time than the leaf material brought to the colonies. Despite the high density of nests and high content of SOM compared to adjacent control soil, CO sub(2) emissions by A. balzani nests represent only 0.3% of the total CO sub(2) efflux by the studied ecosystem. Although these effluxes account for a relative small portion of the total soil CO sub(2) emission, they are still important for the understanding of C balance, especially when one considers the thousands of tons of CO sub(2) emitted each day, across entire Neotropical regions where leaf-cutting ants occur.