Leaf-cutter ants engineer large nitrous oxide hot spots in tropical forests

Though tropical forest ecosystems are among the largest natural sources of the potent greenhouse gas nitrous oxide (N2O), the spatial distribution of emissions across landscapes is often poorly resolved. Leaf-cutter ants (LCA, Atta and Acromyrmex, Myrmicinae) are dominant herbivores throughout Central and South America and influence multiple aspects of forest structure and function. In particular, their foraging creates spatial heterogeneity by concentrating large quantities of organic matter (including nitrogen, N) from the surrounding canopy into their colonies, and ultimately, into colony refuse dumps. Here, we demonstrate that refuse piles created by LCA species Atta colombica in tropical rainforests of Costa Rica provide ideal conditions for extremely high rates of N2O production (high microbial biomass, potential denitrification enzyme activity, N content, and anoxia), and may represent an unappreciated source of heterogeneity in tropical forest N2O emissions. Average instantaneou...