Interactions of biological and herbicidal management of Melaleuca quinquenervia with fire: Consequences for ecosystem services

Exotic plant species invasion can alter ecosystem nutrient dynamics and natural disturbance patterns. The Australian tree Melaleuca quinquenervia has extensively invaded the Florida Everglades and is currently being suppressed using mechanical, herbicidal, and biological control management strategies. While these methods have been evaluated based on reductions in density and abundance of the target weed, other factors should be considered including consequences for ecosystem nutrient storages and interactions with natural disturbances such as fire. We hypothesized that the choice of management tactics, namely herbicidal or biological control, would differentially influence the quantity and availability of soil nutrients before and after a seasonal fire. The management of M. quinquenervia with a herbicide reduced the above- and belowground storage of nutrients both before and after a fire compared to a non-invaded area, while biological control increased storage. There were no differences in nitrogen availability between sites (non-invaded, herbicide, biological control) in the 0–5 cm or 5–15 cm soil depths before or after the fire. Pre-fire phosphorus availability was highest in the non-invaded site in the 0–5 cm soil depth and in the biological control site in the 5–15 cm soil depth. However, phosphorus availability was highest at both depths in the herbicide site post-fire. Biological control of M. quinquenervia using insect herbivores has proven to be effective at controlling plant growth and reproduction. The results of this study suggest that this method may have less of an impact on nutrient storage and cycling than herbicides.