Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2006
Publication Date: 9/1/2007
Citation: Rayamajhi, M.B., Van, T.K., Pratt, P.D., Center, T.D., Tipping, P.W. Melaleuca quinquenervia dominated forests in Florida: analyses of natural-enemy impacts on stand dynamics. Plant Ecology. 192:119-132. 2007. Interpretive Summary: The invasive plant melaleuca of Australian origin has invaded and developed pure forests in many parts of south Florida. It has done so by eliminating other Florida native plants from the area by creating unsuitable environment for other plants. Natural enemies such as plant feeding weevils and psyllids imported from Australia, as well as other insects and pathogens that migrated to the area, defoliated and killed substantial numbers of melaleuca trees. The death of large number of melaleuca trees and the loss of leaves from surviving trees have opened up the forest canopies and created a lot of space on the forest floor. As a result, many native plants were naturally recruited on the forest floor. The return of native plants in previous melaleuca monocultures helped increase the diversity and abundance of native plants in the area. Increases in plant diversity and abundance were more than 5-fold in non-flooded or seasonally flooded sites where melaleuca feeding weevils and psyllids are well established. These findings show that plant feeding insects and disease causing pathogens can be used successfully to rehabilitate sites by promoting the recruitment of native plants.
Technical Abstract: Invasion by the Australian tree, Melaleuca quinquenervia (melaleuca) resulted in near-monoculture stands in vast areas of south Florida. Introduced natural enemies are hypothesized to suppress melaleuca populations and facilitate the return of native species. To test this hypothesis, we used published natural enemy incidence and impact data on melaleuca in the area and monitored stand attributes during 1997 to 2005 at two positions of typical melaleuca stands within three hydrologically delineated habitats. Slow density-decline and basal area increase of melaleuca was associated with the overall plant diversity decline trends in all three habitats during 1997-2001; Myrtaceae and Cyperaceae were the most dominant families during that period. Post 2001, insect and pathogen incidence and impact in melaleuca canopy increased and resulted in an accelerated loss of melaleuca trees in both nonflooded and seasonally flooded habitats. Family and species richness sequence during 1997 was: nonflooded > seasonally-flooded > permanently flooded. At the final assessment, the trend in the family and species compositions for nonflooded (2005) and seasonally-flooded (2004) habitats were similar to 1997 but were of larger magnitudes. The family importance values of Myrtaceae and Cyperaceae were reduced while Asteraceae and Poaceae were increased in both nonflooded and seasonally-flooded habitats. Unlike pre 2001, species diversity and abundance during post 2001 period had increasing trend in nonflooded and seasonally-flooded habitats. The family/species richness and species diversity/abundance were higher in interior than in peripheral plots. These findings show that natural enemy impacts on invasive monocultures facilitate the return of natives and help rehabilitate biologically degraded sites.