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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: Active rehabilitation possibilities for invasive tree occupied sites: Examples from Melaleuca quinquenervia systems in Florida

Authors
item Rayamajhi, Min
item Pratt, Paul
item Center, Ted

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 19, 2012
Publication Date: September 6, 2012
Citation: Rayamajhi, M.B., Pratt, P.D., Center, T.D. 2012. Active rehabilitation possibilities for invasive tree occupied sites: Examples from Melaleuca quinquenervia systems in Florida. Meeting Abstract. PS-4-72.

Interpretive Summary: Accumulated melaleuca litter mass suppresses seedling emergence on forest floor. Removal of melaleuca litter followed by seeding of desired plant species enhanced seedling emergence in melaleuca stands. However, the dynamics of emerged seedlings in litter removed areas of melaleuca over time and space is unknown. Densities of melaleuca seedlings are assumed to be higher initially in melaleuca litter removed forest floors due to the existing soil seedbank, but this invasive plant will be gradually replaced by other native plants in presence of natural enemies such as insects and plant pathogens. We examined these assumptions in mature melaleuca tree stands by conducting temporally sequential experiments in predominantly organic and sandy soils. Results showed best seedling recruitment in both soils when litter was removed and the plots were seeded during wet period. Melaleuca was dominant in both soil types during the first 12-wk evaluation period. Afterward, melaleuca density decreased and the monocots transiently increased in both soil types; other dicots predominated (density-wise) at 96-wk evaluation. There were no changes in sawgrass and wax myrtle densities over the 96-wk. This indicated that the seeds of these species are rare or do not exist in the soil seedbank. Therefore, seed additions of these two or other native plants of choice will be needed in order to actively rehabilitate melaleuca vacated sites. When the plots were protected for additional 84-wk by excluding natural enemies, melaleuca and the native salt-bush (Baccharis sp.) became dominant in terms of canopy-coverage, height, and basal diameter. Suppression of these dominant plant species by natural enemies appeared to enhance the diversity and density of other native plants. These findings show that that the invasive plant dominated sites with thick litter cover can be actively rehabilitated by combining litter removal with seeding of desirable native plant species. Furthermore, natural enemies appear to play a positive role by suppressing invasive plants and thereby enhancing native plant diversity.

Technical Abstract: Accumulated litter mass suppresses seedling emergence on forest floor. This phenomenon was observed in stands of the invasive tree melaleuca tree stands in southern Florida, USA. Removal of melaleuca litter mass has been reported to enhance seedling emergence; however, the dynamics of emerged seedlings in litter removed gaps over time and space is unknown. Melaleuca seedlings are hypothesized to have predominant initial densities which will gradually be replaced by others in presence of its natural enemies. We examined these assumptions in mature melaleuca tree stands by conducting temporally sequential experiments in organic and sandy soils. Results showed best seedling recruitment in both soils when litter was removed and plots were seeded during July-November when soils were wet. Melaleuca was dominant in both soil types during the first 12-wk evaluation period. Melaleuca density decreased whereas other monocots transiently increased in both soil types; other dicots were predominant (density-wise) by 96-wk evaluation time. There were no changes in sawgrass and wax myrtle densities over the 96-wk period, an indication that seeds of these species are rare or nonexistent in the soil seedbank. Seed additions of these two and other native plants may be necessary in order to actively rehabilitate melaleuca vacated sites. When the plots were protected for additional 84-wk by excluding natural enemies, melaleuca and the native salt-bush (Baccharis sp.) became dominant in terms of canopy-coverage, height, and basal diameter. Suppression of these dominant species by natural enemies enhanced the diversity and densities of other native plants. These findings reveal that invasive plant dominated sites with thick litter cover can be actively rehabilitated by combining litter removal with seeding of desirable native plant species. Furthermore, natural enemies appear to play a positive role by suppressing invasive plants and thereby enhancing native plant diversity.

Last Modified: 7/25/2014
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