Alteration of ecosystem nutrient pools and microbial populations after invasion and management of Melaleuca quinquenervia

Ecosystem invasion by exotic plant species poses a significant threat to community biodiversity, function, and stability. Melaleuca quinquenervia is an invasive Australian tree that was introduced into Florida in the early 20^th century. Due to its fire adapted nature and copious seed production, melaleuca is able to out-compete and replace many native species. Perhaps the most successful integrated pest management project in Florida to date has been the effort to control melaleuca in the Everglades.  Inter-agency cooperation has led to the organized use of chemical, mechanical, physical, and biological control methods. While the goal of all these treatment strategies is to reduce exotic populations and restore ecosystem integrity, little work has been done monitoring and evaluating their impact on ecosystem function. In February, 2007 experimental plots were established in Collier County, Florida across five contiguous areas with distinct levels and histories of melaleuca invasion and subsequent management tactics. They include: 1) reproductive melaleuca treated with herbicide, 2) reproductive melaleuca treated with biological control, 3) pre-reproductive melaleuca treated with biological control, 4) pre-reproductive melaleuca with no biological or herbicidal control, and 5) native forest with no melaleuca. Preliminary results reveal that in the early stages of invasion by melaleuca, both the quantity and nutrient concentration of litterfall was significantly reduced. Annual litterfall was 5.5 times higher in the native sites, with 1.9 times higher phosphorus concentration. These results and future biogeochemical and microbial analysis will be used to elucidate the extent, duration, and impact of the changes caused by melaleuca invasion and management.