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Dynamics of the overstorey and species richness in Australian heathlands

Bond, W.J. and Ladd, P.G. (2001) Dynamics of the overstorey and species richness in Australian heathlands. Journal of Mediterranean Ecology, 2 . pp. 247-257.

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Abstract

We studied the impact of overstorey shrubs on under storey richness in three study areas in south-western Australian heathlands. In unburnt heathlands, understorey richness varied inversely with shade cast by the overstorey and was greatest in open sites with no overstorey. Burning increased species richness by as much as 50%. In post-burn sites, understorey richness relative to open sites was significantly lower under sprouting shrubs than under the skeletons of non-sprouters. Sprouters had half the number of species of open sites whereas non-sprouters had the same, or slightly more species at the southern and northern sandplain heath site. However, in burnt Banksia woodlands near Perth, understorey richness was significantly reduced relative to open sites. Understorey composition differed among open sprouter and non-sprouter sites with most species preferring open and non-sprouter sites. We develop a simple model to explore factors influencing understorey diversity. The model predicts that the magnitude and sign of overstorey effects on understorey diversity is strongly influenced by the proportion of species with dormant propagules, since they can survive shading by transient canopies, and by the strength of competitive interactions in the understorey assemblage. We conclude that understorey/overstorey interactions are important for conservation management of these heathlands, and perhaps other vegetation types. However an overstorey may suppress or promote understorey richness, depending on local species traits, and management of overstorey shrubs should vary accordingly.

Publication Type: Journal Article
Murdoch Affiliation: School of Environmental Science
Publisher: Firma Effe s.n.c
URI: http://researchrepository.murdoch.edu.au/id/eprint/17193
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