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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT & EVALUATION OF BIOLOGICAL CONTROL AGENTS FOR INVASIVE SPECIES THREATENING THE EVERGLADES & OTHER NATURAL AND MANANGED SYSTEMS

Location: Invasive Plant Research Laboratory

Title: Rehabilitation of invasive-tree degraded natural areas through biological control: a slow but steady process

Authors
item RAYAMAJHI, MIN
item PRATT, PAUL
item Center, Ted

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Proceedings
Publication Acceptance Date: May 3, 2011
Publication Date: January 15, 2013
Citation: Rayamajhi, M.B., Pratt, P.D., Center, T.D. 2013. Rehabilitation of invasive-tree degraded natural areas through biological control: a slow but steady process. International Symposium on Biological Control of Weeds. FHTET-2012-07/262-264.

Interpretive Summary: Exotic invasive plants can displace native vegetation from natural areas and form monoculture stands. The Australian tree melaleuca impacts natural areas in this manner in southern Florida. Its ability to grow in different environmental conditions coupled with fire resistance, high reproductive potential, and deposition of large quantities of slowly degrading litter on forest floors affects species diversity in melaleuca dominated habitats. Intentionally released biological control agents and adventive natural enemies accelerated defoliation, crown thinning and mortality of melaleuca trees. A 14-year-long field study in south Florida, USA revealed some of the causes and effects of melaleuca invasion and subsequent reversal of effects following the impact of three biological control insects and an adventive rust fungus. During the first 7-year following the release of biocontrol agents, melaleuca densities decreased yielding to increased diversity and abundance of native plants. During the second 7-year period, species diversity decreased slightly as the stature (height and diameter) and sub-canopy coverage of native woody plants increased even though melaleuca continued to occupy the stand-canopy albeit with significantly reduced density and competitive ability to recruit seedlings and occupy canopy gaps. These melaleuca affected areas are not fully restored to their pre-melaleuca invasion state but are being rehabilitated nearer to their original state as reflected by the return of native plants resulting in enhanced biodiversity.

Technical Abstract: Natural areas invaded by invasive exotic plants can develop into monocultures as native plants are displaced. The Australian tree Melaleuca quinquenervia (melaleuca) impacts natural areas in this manner in southern Florida. Environmental plasticity coupled with fire resistance, high reproductive potential, and deposition of large quantities of slowly degrading litter on forest floors affects species diversity in melaleuca dominated habitats. Intentionally released biological control agents and adventive natural enemies accelerated defoliation, crown thinning and mortality of melaleuca trees. A 14-year-long field study in south Florida, USA revealed some of the causes and effects of melaleuca invasion and subsequent reversal of effects following the impact of three biological control insects and an adventive rust fungus. During the first 7-year following the release of biocontrol agents, melaleuca densities decreased yielding to increased diversity and abundance of native plants. During the second 7-year period, species diversity decreased slightly as the stature (height and diameter) and sub-canopy coverage of native woody plants increased even though melaleuca continued to occupy the stand-canopy albeit with significantly reduced density and competitive ability to recruit seedlings and occupy canopy gaps. These melaleuca degraded stands are not fully restored to their pre-melaleuca invasion state but are being rehabilitated nearer to their original state as reflected in the return of native plant species and enhanced biodiversity.

Last Modified: 9/10/2014
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