Management regimes for a plant invader differentially impact resident communities
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Published source details
Mason T.J. & French K. (2007) Management regimes for a plant invader differentially impact resident communities. Biological Conservation, 136, 246-259.
Published source details Mason T.J. & French K. (2007) Management regimes for a plant invader differentially impact resident communities. Biological Conservation, 136, 246-259.
Summary
Bitou bush Chrysanthemoides monilifera rotundata (a South African shrub) was introduced to Australia in the early 20th century where planted extensively in coastal New South Wales to stabilise sand dunes. This study evaluated the success of intensive and extensive management regimes in controlling bitou which has become highly invasive in large areas of dune habitats and impacted on native coastal plant communities.
Study area: The study area covered approximately 1,330 km of coastal dune system subject to bitou invasion and long-term control in New South Wales (28º12′14″ S; 153º34′ 04″ E to 36º57′37″ S; 149º56′07″ E).
Sampling: Sampling was conducted at 99 sites in fore and hind dune communities (see below) throughout the study area between September 2002 and May 2003. Quadrats (20 × 50 m) were randomly positioned, within which vascular species, bryophyte and lichen abundances, and environmental variables were recorded. Information on confounding factors e.g. time since the most recent fire, and details of previous control methods were obtained.
Fore dune communities: The fore dune sites were divided into four invasion categories:
i) 'non-invaded' sites (n = 17) with low bitou cover (average 5%) and no control. Although not pristine, these were the least disturbed and thus best represented original dune communities;
ii) 'intensively managed' sites (n = 19) with control of bitou by labour-intensive methods e.g. hand removal and direct application of herbicide (mostly glyphosate) to cut stems or foliage.
iii) 'extensively managed' (n = 13) sites with control of bitou mostly by aerial herbicide spraying (again mostly glyphosate);
iv) 'bitou-invaded' sites (n = 16) with high bitou cover (average 60%) and no control.
Hind dune communities: Ten non-invaded, 12 managed (at most sites, control was intensive, mostly comprising foliar application of herbicide by backpack spraying, herbicide application to cut stems, and hand removal) and 12 bitou-invaded sites were surveyed.
At all sites, native species richness, exotic species richness, species composition and bitou seedling abundance were used to assess responses to the different control regimes.
Extensive management (i.e. aerial spraying) resulted in native species composition less similar than non-invaded sites in comparison to an intensive management approach (e.g. manual control and targeted herbicide application) which resulted in plant composition closer to native communities. However, intensively managed sites had more exotic plant species, one or more of which could potentially replace the original invader (i.e. bitou).
The positive effects of management evident on some fore dunes were not found in hind dunes, where managed sites had the highest exotic species richness and bitou seedling abundance appeared little affected by management. Plant communities in managed hind dunes were also compositionally distinct from non-invaded sites. Thus fore and hind dune communities exhibited different responses to bitou control.
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