Disturbancemediated competition the interacting

Authors: Shon S Schooler Tony Cook Graham Prichard Alice G Yeates

Publish Date: 2010/02/21

Volume: 12, Issue: 9, Pages: 3289-3298

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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 cooccurring competitor plants the introduced grass kikuyu Pennisetum clandestinum and the native grass couch Cynodon dactylon over a 2year 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 975 and the combination of selective herbicide and mowing reduced the biomass of alligator weed significantly more than herbicide alone by 986 compared with unmanipulated 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 poolWe thank Drew Johnston for the use of his property for the trial site Celine ClechGoods and Gio Fichera assisted greatly in the collection and processing of biomass samples Rieks van Klinken and two anonymous reviewers provided constructive comments that significantly improved this manuscript Funding was provided to S Schooler by LW Australia and DAFF through the Defeating the Weed Menace Program and by the Australian Weed Research Centre

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