Leaf-cutting ant (Atta cephalotes) nests may be hotspots of methane and carbon dioxide emissions in tropical forests

Abstract

Leaf-cutting ants of the genus Atta are widely distributed throughout the American tropics and subtropics and rival other herbivores in the consumption of surrounding foliage. Although numerous studies have been conducted on the role these insects play in herbivory and organic matter dynamics, only a handful of studies have examined their impacts on soil greenhouse gas emissions. Our study investigated fluxes of carbon dioxide (CO2) and methane (CH4) from three nests of Atta cephalotes using a portable greenhouse gas analyzer, and measured CO2 and CH4 emissions from soils containing nest holes that ranged 5.2–152.1 g CO2-C and −1.1 to 15,264.7 mg CH4-C m-2 day-1, respectively. Fluxes of CO2 and CH4 were positively correlated above nest holes, but not in patches of soil away from leaf-cutting ant nests. Nearby non-nest soil emissions were significantly lower, ranging from 0.6 to 6.0 g CO2-C and −1.3 to 0.77 mg CH4-C m-2 day-1. Fluxes of both gases among nests and among holes within a single nest were highly variable. This preliminary dataset is small in scale both temporarily and geographically, but the discovery of substantial greenhouse gas fluxes from Atta cephalotes nests may have important implications for carbon budgets of tropical and subtropical American forests. Further work will be necessary to determine the mechanisms behind enhanced greenhouse gas emissions from leaf-cutting ant nests, and how this may alter ecosystem-scale CO2 emissions and CH4 sink strength in tropical forest soils.