Plant species richness responses to grazing protection and degradation history in a low productivity landscape

Fensham, R. J., Silcock, J. L. and Dwyer, J. M. (2011) Plant species richness responses to grazing protection and degradation history in a low productivity landscape. Journal of Vegetation Science, 22 6: 997-1008. doi:10.1111/j.1654-1103.2011.01305.x

Author Fensham, R. J.
Silcock, J. L.
Dwyer, J. M.
Title Plant species richness responses to grazing protection and degradation history in a low productivity landscape
Journal name Journal of Vegetation Science   Check publisher's open access policy
ISSN 1100-9233
Publication date 2011-12-01
Sub-type Article (original research)
DOI 10.1111/j.1654-1103.2011.01305.x
Volume 22
Issue 6
Start page 997
End page 1008
Total pages 12
Place of publication Grangaerde, Sweden
Publisher Opulus Press
Language eng
Formatted abstract
Questions: Does species richness and abundance accumulate with grazing protection in low productivity ecosystems with a short evolutionary history of grazing, as predicted by emerging theory? How do responses to grazing protection inform degradation history?
Location: Mulga (Acacia aneura) dry forest, eastern Australia, generally considered chronically degraded by livestock grazing.
Methods: Three paired exclosures (ungrazed, and macropod-grazed) were compared with open-grazed areas after 25 years using quadrats located on either side of the fences. Additionally, the regional flora for mulga dry forest was assessed to identify species that may have declined and could be threatened by grazing.
Results: Low herbaceous biomass accumulation (<1.3 t ha−1) with full grazing protection confirmed a low productivity environment. For most plant life forms the highest species richness was in macropod-grazed exclosures, an intermediate grazing disturbance that best approximates the evolutionary history of the environment. This was the net outcome of species that both declined and increased in response to grazing. Regeneration and subsequent self-thinning of mulga was promoted with grazing protection, but did not confound interpretation of species richness and abundance responses. At the regional scale only 11 native species out of 407 comprising the mulga dry forest flora were identified as rare and potentially threatened by grazing.
Conclusions: Significant increases in richness or abundance of native plants with grazing protection, persistence of perennial grasses, regeneration of mulga and scant evidence of a major decline in the regional flora are not consistent with established assertions that long-grazed mulga dry forest has crossed functional thresholds that limit recovery. Further, a peak in species richness under intermediate (macropod) grazing is counter to the shape of the response predicted by emerging theory for recovery of species richness in a low productivity environment. The finding prompts a more thorough understanding of the distinction between environments with inherently low productivity and those degraded by grazing.
Keyword Disturbance-diversity models
Intermediate disturbance
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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