Disturbance-mediated competition: the interacting roles of inundation regime and mechanical and herbicidal control in determining native and invasive plant abundance |
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Authors: | Shon S Schooler Tony Cook Graham Prichard Alice G Yeates |
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Institution: | (1) CSIRO Entomology, 120 Meiers Rd., Indooroopilly, QLD, 4068, Australia;(2) NSW Department of Primary Industries, 4 Marsden Park Rd, Calala, NSW, 2340, Australia;(3) Port Stephens Council, PO Box 42, Raymond Terrace, NSW, 2324, Australia;(4) School of Biological Sciences, University of Queensland, St Lucia, QLD, 4072, Australia |
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Abstract: | Disturbance is a key component of many successful plant invasions. However, interactions among natural and anthropogenic disturbances
and effects of these interacting disturbances on invasive plants and desired vegetation are rarely examined. We investigated
the effect of anthropogenic disturbance (herbicidal and mechanical) along a natural inundation gradient (20–282 days) on the
biomass and resource allocation of the invasive wetland plant, alligator weed (Alternanthera philoxeroides), and two co-occurring competitor plants, the introduced grass, kikuyu (Pennisetum clandestinum), and the native grass, couch (Cynodon dactylon), over a 2-year period. In the absence of additional disturbance, kikuyu biomass was negatively affected, alligator weed
biomass was positively affected, and couch biomass was not affected by inundation disturbance. In addition, kikuyu was not
affected by the selective removal of alligator weed, while couch increased in wetter habitats where kikuyu was absent due
to inundation stress. This suggests that kikuyu is a superior competitor in drier habitats and inundation facilitates the
invasion of alligator weed, while couch is an inferior competitor to both kikuyu and alligator weed and is therefore suppressed
across its entire niche by these two introduced species. Mowing alone had no effect on the biomass of the species, suggesting
the plants are equally tolerant of shoot removal. Selective herbicide reduced alligator weed biomass by 97.5% and the combination
of selective herbicide and mowing reduced the biomass of alligator weed significantly more than herbicide alone, by 98.6%
compared with un-manipulated controls. To predict community change and prevent sequential exotic plant invasions after weed
removal, it is necessary to consider the interacting effects of disturbance and the niche space of invasive species in the
local propagule pool. |
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