Print PageEcosystem function in terrestrial systems often depends on linkages between aboveground and belowground processes. Links between aboveground and belowground systems can have disproportionate impacts on ecosystem function if nutrients produced or released in one subsystem (e.g., labile carbon through photosynthesis) limit productivity in the other. Organisms that amplify such linkages are thus important research foci, particularly in hyperdiverse systems like wet tropical forests. Here, we report a study conducted on Barro Colorado Island in Panama in which we tested whether refuse generated from colonies of the ant Azteca trigona affects decomposition rates and arthropod community structure in a brown food web. A. trigona build large, hanging, conical nests, which funnel refuse from colony activities to the leaf litter community below. We predicted that 1) decomposition rates would be faster under Azteca nests, and 2) this accelerated decomposition would be caused by refuse addition.
Results/Conclusions
We found support for the first prediction using an observational study, which showed that cellulose and wood decomposition rates were significantly higher under Azteca nests than in locations 10m away from the nest. We found support for the second prediction in an experimental study in which we added either refuse, soil, or nothing to randomly selected forest plots over the course of six weeks, and measured the effect of these treatments on decomposition. We found that the addition of refuse (but not soil) significantly increased decomposition rates of both cellulose and wood. Effects were large; for example, refuse addition in the experimental study increased cellulose decomposition by 75% after 4 weeks. Refuse effects on decomposition were associated with increased arthropod abundance and changes in arthropod community structure. Given the magnitude and scope of their impact, our results suggest that Azteca ants may be an important connector of ecosystem processes in this system.
