Are competitive effects of native species on an invader mediated by water availability?
Article first published online: 27 FEB 2012
© 2012 International Association for Vegetation Science
Journal of Vegetation Science
Volume 23, Issue 4, pages 657–666, August 2012
How to Cite
Mason, T. J., French, K., Russell, K. (2012), Are competitive effects of native species on an invader mediated by water availability?. Journal of Vegetation Science, 23: 657–666. doi: 10.1111/j.1654-1103.2012.01393.x
- Issue published online: 3 JUL 2012
- Article first published online: 27 FEB 2012
- Manuscript Accepted: 3 JAN 2012
- Manuscript Received: 6 MAR 2011
- Land and Water Australia
- NSW Environmental Trust
- Climate change;
- Coastal dune community;
- Competitive intensity;
- Exotic species;
- Invasive species
Climate change processes could influence the dynamics of biotic interactions such as plant competition, especially in response to disturbance phenomena such as invasional processes. Are competitive effects of native species on an invader mediated by water availability?
Glasshouse facility, New South Wales, Australia.
We constructed competitive hierarchies for a representative suite of species from coastal dune communities that have been invaded by the Asteraceae shrub, bitou (Chrysanthemoides monilifera subsp. rotundata). We used a comparative phytometer approach, where the invader species was grown with or without a suite of native species in glasshouse trials. This was used to construct competition hierarchies under two water stress conditions: non-droughted and droughted. The treatments were designed to simulate current and potential future water availability respectively.
We found that the invader experienced fewer competitive effects from some native species under water stress, particularly with regard to below-ground biomass effects. Native species were often poor competitors with the invader, despite their adaptation to periodic water stress in native coastal environments. Of the native species with significant competitive effects on the invader, functionally similar shrub species were the most effective competitors, as expressed in below-ground biomass. The relative position of species in the hierarchy was consistent across water treatments based on below-ground bitou biomass, but was contingent on water treatment when based on above-ground bitou biomass.
The competitive effects of native species on an invader are affected by water stress. While the direction of response to water stress is species-specific, many species have small competitive effects on the invader under droughted conditions. This could allow an increase in invader dominance with climate change.