Effects of flood timing and livestock grazing on exotic annual plants in riverine floodplains
Article first published online: 6 AUG 2012
© 2012 The Authors. Journal of Applied Ecology © 2012 British Ecological Society
Journal of Applied Ecology
Volume 49, Issue 5, pages 1131–1139, October 2012
How to Cite
Lunt, I. D., Jansen, A., Binns, D. L. (2012), Effects of flood timing and livestock grazing on exotic annual plants in riverine floodplains. Journal of Applied Ecology, 49: 1131–1139. doi: 10.1111/j.1365-2664.2012.02176.x
- Issue published online: 20 SEP 2012
- Article first published online: 6 AUG 2012
- Manuscript Accepted: 18 JUN 2012
- Manuscript Received: 1 DEC 2011
- environmental water;
- exotic plant species;
- invasion ecology;
- Mediterranean annuals;
- river restoration
- Riverine floodplains around the world are highly prone to invasions by exotic species. While many processes have contributed to floodplain invasions, two theories have received particular attention: (i) replacement of native perennials by exotic annuals following historical livestock grazing and (ii) ‘terrestrialization’ because of fewer floods following river regulation.
- We assessed how exclusion of grazers and flooding in different seasons affected established populations of exotic annuals in an 8-year experiment. We hypothesized that effects of season of flooding would vary depending on timing in relation to annual plant life cycles and that outcomes may be affected by interactions between grazing and flooding.
- Flooding in any season reduced exotic annuals to <2% cover and converted a dryland flora dominated by exotic annuals to a wetland flora dominated by native perennials. However, flood effects may be short lived, as areas flooded in 1 year supported abundant exotics the next. Grazer exclusion and interactions between grazing and flooding did not affect cover of exotic annuals, although grazing depleted native perennials in recently flooded areas.
- Synthesis and applications. Consistent with the terrestrialization hypothesis, short-duration floods provide a practical method for controlling exotic annual plants where river regulation has reduced the frequency of natural floods. As exotic impacts are greatest in dry periods, when exotics are most abundant, ecosystem benefits will be greatest when flooding leads to a protracted decline in exotic annuals during the dry (non-inundated) years following flood recession. Otherwise, reductions in exotic annuals may be transient and have little positive impact on floodplain ecosystems and processes.