AOBPreview originally published online on March 8, 2009
Annals of Botany 2009 103(7):1129-1143; doi:10.1093/aob/mcp047
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Population dynamics along a primary succession gradient: do alpine species fit into demographic succession theory?
1 Institute of Botany, University of Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria
2 Department of Ecological Modelling, UFZ Helmholtz Centre for Environmental Research, Permoserstr. 15, D-04318 Leipzig, Germany
* For correspondence. E-mail brigitta.erschbamer{at}uibk.ac.at
Received: 22 July 2008 Returned for revision: 27 October 2008 Accepted: 16 January 2009 Published electronically: 8 March 2009
Background and Aims: Understanding processes and mechanisms governing changes in plant species along primary successions has been of major importance in ecology. However, to date hardly any studies have focused on the complete life cycle of species along a successional gradient, comparing pioneer, early and late-successional species. In this study it is hypothesized that pioneer species should initially have a population growth rate, 
, greater than one with high fecundity rates, and declining growth rates when they are replaced by late-successional species. Populations of late-successional species should also start, at the mid-successional stage (when pioneer species are declining), with growth rates greater than one and arrive at rates equal to one at the late successional stage, mainly due to higher survival rates that allow these species to persist for a long time.
Methods: The demography of pioneer- (Saxifraga aizoides), early (Artemisia genipi) and late-successional species (Anthyllis vulneraria ssp. alpicola) was investigated together with that of a ubiquitous species (Poa alpina) along the Rotmoos glacier foreland (2300–2400 m a.s.l., Central Alps, Austria) over 3 years. A matrix modelling approach was used to compare the main demographic parameters. Elasticity values were plotted in a demographic triangle using fecundity, individual growth and survival as vital rates contributing to the population growth rates.
Key Results: The results largely confirmed the predictions for population growth rates during succession. However, high survival rates of larger adults characterized all species, regardless of where they were growing along the succession. At the pioneer site, high mortality rates of seedlings, plantlets and young individuals were recorded. Fecundity was found to be of minor relevance everywhere, but it was nevertheless sufficient to increase or maintain the population sizes.
Conclusions: Demographically, all the species over all sites behaved like late-successional or climax species in secondary successions, mainly relying on survival of adult individuals. Survival serves as a buffer against temporal variation right from the beginning of the primary succession, indicating a major difference between primary and secondary succession.
Key words: Demography, elasticity, glacier foreland, matrix model, population growth, primary succession, strategy, Saxifraga aizoides, Artemisia genipi, Anthyllis vulneraria ssp. alpicola, Poa alpina
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