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Population structure of Artemisia genipi in a glacier foreland of the Central Alps

Population structure of Artemisia genipi in a glacier foreland of the Central Alps. Erich Schwienbacher & Brigitta Erschbamer Institute of Botany University of Innsbruck. e. V. Club Allegra München. Contact: erich.schwienbacher@uibk.ac.at. Introduction. Plant community level.

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Population structure of Artemisia genipi in a glacier foreland of the Central Alps

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  1. Population structure of Artemisia genipi in a glacier foreland of the Central Alps Erich Schwienbacher & Brigitta Erschbamer Institute of Botany University of Innsbruck e. V. Club Allegra München Contact: erich.schwienbacher@uibk.ac.at

  2. Introduction Plant community level • Change of species composition Population level • Change of population structure • Number of individuals • Life stage spectrum Primary succession in an ecosystem

  3. Levels of successional changes Population Rabotnov (1945), White (1985), Urbanska (1992) Species 1 Species 2 Species 3 Population size Plant community Time Type A Type B Type C Time Succession Stage X Stage Y Stage Z Time Invasion Optimum Regression

  4. Hypotheses For early successional species: • Successional stage Population density Dominating life stage • (I) Young Young (II) Middle aged Balanced (III) Old Old Population structure changes according to the chronosequence of the successional stages (IV) Population density and life stage spectrum correlate with coverage of vegetation and coverage of bare soil, respectively

  5. Species • Artemisia genipi Weber • Family: Asteraceae • Endemic of the Alps • In the alpine & subnival belt In the glacier foreland  early successional species

  6. ROTMOOSFERNERTyrol, Austria 2001 1956 Glacier foreland 1921 Extension of the glacier in the Little Ice Age 1858 2300 - 2500 m a.s.l. 46°49‘N 11°02‘E

  7. Study site

  8. Design of the experiment • 2 sections of the study site: • Younger section • Older section 15 plots each • 3 groups of plot surface types: • Coverage of bare soil • Low < 40 % • Medium 40 - 55 % • High > 55 % 5 plots each Plots: n = 30 á 1 m²

  9. Design of the experiment

  10. Single census of plots in 2001 For each individuum: Number of inflorescences Life stages Diameter of cushion Number of rosettes • Number of individuals per plot

  11. Characterisation of life stages Vegetative Small 1 - 3 > 0.5 cm Generative Vegetative ___ Medium 4 - 6 Generative Vegetative ___ Large > 6 Generative Life stages State of reproduction Plant size Number of rosettes Diameter of cushion Seedlings/Juveniles Vegetative 1 <= 0.5 cm

  12. Results

  13. Comparison of Younger and Older section Seedlings/Juveniles p < 0.05 Small p > 0.05 Medium p > 0.05 Large p > 0.05 Sum of all life stages p < 0.05 No. of indv. * life stage-1 * plot-1 (mean + stddev) n = 30 Section of study site

  14. Comparison of Younger and Older section Small-Generative Medium-Vegetative Medium-Generative Large-Vegetative Large-Generative Not significant! Number of individuals Life stage: Small-Vegetative

  15. Comparison of surface types For all life stages Not significant! Number of individuals Life stage: Seedlings/Juveniles p > 0.05 < 40 40 - 55 > 55 [%]

  16. Cluster analysis of population census data - + - - - + ++ + - - - - - - - - ++ +++ + - Dendrogram Seedlings Small Medium Large & Juveniles 0 5 10 15 20 25 +---------+---------+---------+---------+---------+ ‚Highly dense‘ ‚Dense‘ ‚Sparse‘ Plots n = 30 Median-Method with Squared Euclidean Distance ‚Transient‘

  17. Distribution of population types in the field ‚Transient‘ - - - - - - - ‚Sparse‘ - + - - - ‚Dense‘ + ++ + - ‚Highly dense‘ ++ +++ + - Study site Seedlings Small Medium Large & Juvenile Plot Older section Younger section

  18. Coverage of bare soil due to population types Invasive population types p > 0.05 ‚Highly dense‘ ‚Transient‘ ‚Sparse‘ ‚Dense‘

  19. Summary • Population types • A change in the life stage spectrum following • Invasion  Optimum  Regression • could not be proved • Decreasing number of Seedlings/Juveniles • With proceeding primary succession • Decreasing population density • Decreasing number of Small-Vegetative life stages • Small individuals are dominant in all population types • No correlation found between coverage of bare soil and population • density or population structure, respectively

  20. Conclusion Thank you for your attention! In a rapidly changing ecosystem such as a glacier foreland early successional species may not establish balanced population structures Long term studies are necessary to know more about the dynamics of such populations Best thanks to the colleagues of the Univ. of Innsbruck Contact: erich.schwienbacher@uibk.ac.at Contact: erich.schwienbacher@uibk.ac.at Contact: erich.schwienbacher@uibk.ac.at Contact: erich.schwienbacher@uibk.ac.at Contact: erich.schwienbacher@uibk.ac.at Contact: erich.schwienbacher@uibk.ac.at

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