Turf wars: experimental tests for alternative stable states in a two-phase coastal ecosystem

Brownstein, Gretchen, Lee, William G., Pritchard, Daniel W. and Wilson, J. Bastow (2014) Turf wars: experimental tests for alternative stable states in a two-phase coastal ecosystem. Ecology, 95 2: 411-424. doi:10.1890/12-1982.1

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Author Brownstein, Gretchen
Lee, William G.
Pritchard, Daniel W.
Wilson, J. Bastow
Title Turf wars: experimental tests for alternative stable states in a two-phase coastal ecosystem
Journal name Ecology   Check publisher's open access policy
ISSN 0012-9658
1939-9170
Publication date 2014-02-01
Sub-type Article (original research)
DOI 10.1890/12-1982.1
Open Access Status File (Publisher version)
Volume 95
Issue 2
Start page 411
End page 424
Total pages 14
Place of publication Ithaca, NY, United States
Publisher Ecological Society of America
Language eng
Formatted abstract
Alternative stable states have long been thought to exist in natural communities, but direct evidence for their presence and for the environmental switches that cause them has been scarce. Using a combination of greenhouse and field experiments, we investigated the environmental drivers associated with two distinctive herbaceous communities in coastal ecosystems in New Zealand.

In a mosaic unrelated to micro-topography, a community dominated largely by native turf species (notably Leptinella dioica, Samolus repens, and Selliera radicans) alternates with vegetation comprising exotic (i.e., nonnative) pasture species (notably Agrostis stolonifera, Holcus lanatus, Lolium perenne, and Trifolium repens). The species of these two communities differ in functional characters related to leaf longevity and growth rate, and occupy soils of differing nitrogen levels.

Both spatial and environmental factors influenced the species composition locally. Reciprocal transplants of soil, with and without associated vegetation, showed that a native turf community developed when sward or soil from either community was bounded by turf, and a pasture community developed when sward or soil from either community was surrounded by pasture. In artificial mixed communities in the greenhouse, turf was able to invade the pasture community where the vegetation was clipped to simulate grazing, and also where Trifolium was removed and/or salt spray was applied. The pasture community invaded the turf where Trifolium was present or nitrogen was added. These results were supported by trends in experimentally manipulated field plots, where the amount of turf cover increased when nitrogen was kept low and when salt spray was applied, whereas pasture cover increased in the absence of salt spray.

Thus, persistence of the native turf community is dependent on grazing, both directly and via its effect on keeping nitrogen levels low by excluding the exotic, nitrogen-fixing Trifolium, and by exposing the vegetation to salt spray. If any of these factors change, there could be a state change to pasture dominance that might be resistant to reversion to turf. Managing such coastal herbaceous communities therefore requires an understanding of the environmental and species characteristics that maintain alternative states.
Keyword Alternative stable state
Coastal turf ecosystems
Dunedin, South Island, New Zealand
Functional traits
Grazing
Invasion
Nitrogen
Positive feedback switch
Salt spray
Trifolium repens
Vegetation mosaic
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Centre for Mined Land Rehabilitation Publications
Official 2015 Collection
Sustainable Minerals Institute Publications
 
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Created: Thu, 06 Mar 2014, 18:09:07 EST by Gretchen Brownstein on behalf of Sustainable Minerals Institute