An invasive producer (albizia) and predator (coqui frogs) alter decomposition processes in a Hawaiian tropical forest

A litterbag experiment using different mesh sizes and naphthalene examined the potential of invasive tree species Falcataria moluccana and Elutherodactylus coqui frogs to alter decomposition rates and shift the relative importance of microbial versus invertebrate decomposers. Mixed litter litterbags were placed in invaded F. moluccana forests with and without E. coqui frogs and in native Metrosideros polymorpha forests with and without E. coqui frogs. Leaf litter decomposition rates were significantly higher in F. moluccana-invaded forests with E. coqui frogs, with invertebrate decomposers responsible for the majority of decomposition. The interaction between these invasive species also affected site quality, possibly by increasing primary productivity and nutrient availability resulting in faster decomposition rates. A combination of bottom-up and top-down sources may be the stimulus of the invertebrate detritivores. The accumulation of high quality leaf litter from F. moluccana and the nutrient-rich excreta from E. coqui may have served as a good food source for invertebrates. Top-down effects from E. coqui may have shifted the decomposer community composition. Because these two invasive species further enhanced the alteration of decomposition rates more than they did alone, an invasional meltdown may be occurring and potentially altering ecosystem function.