Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/3/2010
Publication Date: 6/4/2010
Citation: Martin, M.R., Tipping, P.W., Reddy, K.R., Daroub, S.M., Roberts, K.M. 2010. Interactions of biological and herbicidal management of Melaleuca quinquenervia with fire: Consequences for ecosystem services. Biological Control, Vol. 54, Issue 3, pps. 307-315. Interpretive Summary: Many natural systems are managed to maximize the delivery of ecosystem services such as space for recreational activities, wildlife habitat, and maintenance of biological diversity. Determining the best management practices for exotic species requires consideration of a broad array of factors and their potential interactions, including future interactions with natural events like fires. However, few studies have evaluated the effects of management programs on the delivery of less obvious, but no less important, ecosystem services like nutrient storage. Most efforts to date have emphasized above-ground factors like plant and animal diversity and richness, with little to no consideration of below-ground factors like nutrient storage, nutrient cycling, and microbial community biomass. This study documents how these foundational ecosystem components were affected by the management of exotics in the backdrop of a natural fire event. In this study, the invasion and management of M. quinquenervia caused significant and persistent changes in the aboveground litter storage, storage and availability of nutrients, and soil microbial communities in a sub-tropical wetland forest. Changes in the storage and availability of nutrients may have unpredictable effects on ecosystem structure and function in the future. For example, although minimum levels of nitrogen and phosphorus availability are needed for maintenance of soil microbial communities and to support regrowth by native plants after disturbances such as fire, any nitrogen or phosphorus produced in excess of these needs may be vulnerable to loss by leaching and erosion with negative consequences for downstream ecosystems. 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 had less of an impact on nutrient storage and cycling than did herbicides.
Technical Abstract: An example of a successful integrated pest plant management program is the Melaleuca quinquenervia (Cav.) Blake project in the Florida Everglades. Mechanical, chemical, and biological control methods have been used in concert to eliminate large monotypic stands while containing future population expansion by suppressing the invasive potential of M. quinquenervia. Although these programs have been evaluated based on the quantity of plant biomass removed or reduction in rates of exotic population spread, other evaluation factors deserving consideration include the impact on non-target vegetation, the recovery of native plant communities, the alteration of ecosystem function, and the interactions with natural disturbances like seasonal fires. This study tested the hypothesis that the choice of management tactics for M. quinquenervia influenced the quantity and availability of nutrients before and after a seasonal fire. Herbicide control of M. quinquenervia reduced the above- and belowground storage of nutrients both before and after a seasonal fire while biological control resulted in increased storage. There were no differences in nitrogen availability among treatment sites (non-invaded, herbicide, biological) 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 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 is effective at controlling plant growth and reproduction and this study also found this method had less of an impact on nutrient storage and cycling than herbicides. Although herbicides remain a valuable tool in the management of invasive species, their potential consequences for ecosystem structure and function should be evaluated, especially below ground components like microbial population dynamics.