Submitted to: Aquatic Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2011
Publication Date: 8/26/2011
Citation: Martin, M.R., Tipping, P.W., Reddy, K.R., Madeira, P.T., Fitzgerald, D. 2011. An evaluation of the impact of Melaleuca quinquenervia invasion and managment on plant community structure after fire. Aquatic Botany. 95:287-291. Interpretive Summary: Herbicidal and biological management programs aim to reduce the size and spread of invasive species populations in order to allow native plant communities to recover. However, the impact of various treatment methods on plant community structure and re-invasion potential of exotic species often remains unexamined. We compared changes in plant community structure in a P. elliottii-T. distichum ecotone forest after the invasion and management of M. quinquenervia by asking if the choice of invasive plant management strategy, namely herbicidal or biological, alters plant community assemblages and the re-invasion potential of M. quinquenervia after a seasonal fire. In this study, herbicidal and biological management of M. quinquenervia resulted in lower levels of plant diversity after a seasonal fire when compared to an unmanaged, non-invaded site, although the herbicide site contained levels of species richness comparable to the non-invaded site. While the herbicide site contained levels of species richness comparable to the non-invaded site, only 57% of the plant species were found in common compared to 70% of species in biological site. Although the density of M. quinquenervia seedlings was highest in the biological control site compared to the non-invaded and herbicide sites, the scale of M. quinquenervia re-invasion in the all sites is significantly lower than experienced in the same site prior to the introduction of biological control agents. While the ultimate goal of management programs is to restore ecosystem integrity, this work has shown that passive restoration after management may not be enough to restore plant community structure in these systems.
Technical Abstract: The successful management of invasive species can be particularly difficult in natural areas that depend on disturbances such as fire to maintain community structure and function. In these systems, fire-adapted invasive species may disproportionally benefit from post-fire resource availability, increasing coverage and abundance. We established twenty-five, 1 m2 plots after a fire in areas invaded by Melaleuca quinquenervia and then managed either with herbicides or biological control. A native forest (non-invaded) with no M. quinquenervia was also included in the evaluation. Non-woody plant species richness was measured in each plot while four, 100 m2 plots were established per treatment type for measuring woody plant richness. Non-woody plant species richness was highest in the non-invaded and herbicide sites compared to the biological control site. Woody plant species richness was highest in the non-invaded site followed by the biological control site and then the herbicide site. The abundance of M. quinquenervia live and dead seedlings was highest in the biological control compared to the non-invaded and herbicide sites. While the ultimate goal of management programs is to restore ecosystem integrity, this work provides one line of evidence that passive restoration after treatment may not be enough to restore plant community structure in this system.