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Population structure of Artemisia genipi
in a glacier foreland of the Central Alps
e. V. Club Allegra
München
Erich Schwienbacher & Brigitta Erschbamer
Institute of BotanyUniversity of Innsbruck
Contact: [email protected]
Primary succession in an ecosystem
• Change of species composition
Plant community level
Introduction
Population level
• Change of population structure
– Number of individuals– Life stage spectrum
Levels of successional changes
Invasion Optimum Regression
Time
Type A Type B Type C
Plant community
Time
Stage X Stage Y Stage ZSuccession
Rabotnov (1945), White (1985), Urbanska (1992)
Time
Pop
ulat
ion
size Species 1 Species 2 Species 3
Population
Hypotheses
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
(II) Middle aged Balanced
(III) Old Old
For early successional species:
Successional stage Population density Dominating life stage
(I) Young Young
Species
Artemisia genipi Weber
Family: Asteraceae
• Endemic of the Alps
• In the alpine & subnival belt
In the glacier foreland early successional species
ROTMOOSFERNERTyrol, Austria
2300 - 2500 m a.s.l. 46°49‘N 11°02‘E
1921
1956
2001
Glacier forelandExtension of the glacier in the Little Ice Age 1858
Study site
Design of the experiment
Plots: n = 30 á 1 m²
2 sections of the study site:
• Younger section
• Older section
3 groups of plot surface types:
Coverage of bare soil• Low < 40 %• Medium 40 - 55 %• High > 55 %
15 plots each
5 plots each
Design of the experiment
Single census of plots in 2001
• Number of individuals per plot
Life stages
For each individuum:
Number of inflorescences
Diameter of cushion Number of rosettes
Characterisation of life stages
Number ofrosettes
Plant size
Diameter of cushion
State of reproduction
1 <= 0.5 cmVegetativeSeedlings/Juveniles
1 - 3 > 0.5 cmVegetative
GenerativeSmall
4 - 6 ___Vegetative
GenerativeMedium
> 6 ___Vegetative
GenerativeLarge
Life stages
Results
Comparison of Younger and Older section
0
20
40
60
Younger Older
Indi
v/m
²
n = 30Sum of all life stages
p < 0.05
No. of indv. * life stage-1 * plot-1 (mean + stddev)
p < 0.05
Seedlings/Juveniles
p > 0.05
Small
p > 0.05
Medium
p > 0.05
Large
Section of study site
p < 0.05
Younger Older
0
40
80
120
Indi
v./m
²
Comparison of Younger and Older section
Life stage: Small-Vegetative
Small-Generative
Medium-Vegetative
Medium-Generative
Large-Vegetative
Large-Generative
Not significant!
Number of individuals
Coverage of bare soil
0
25
50
75
100
Indi
v./m
²
Comparison of surface types
Life stage: Seedlings/Juveniles
For all
life stages
Not significant!
p > 0.05
< 40 40 - 55 > 55 [%]
Number of individuals
Cluster analysis of population census data
Median-Method with Squared
Euclidean Distance
Seedlings Small Medium Large& Juveniles
++ +++ + - + ++ + -
- - - - - - -
- + - - -
Dendrogram
‚Transient‘
‚Sparse‘
‚Dense‘
‚Highly dense‘
Plots n =
30
0 5 10 15 20 25+---------+---------+---------+---------+---------+
Distribution of population types in the field
Seedlings Small Medium Large & Juvenile
Older section
Younger section
Plot Study site
- - - - - - -
‚Transient‘
- + - - -
‚Sparse‘
+ ++ + -
‚Dense‘
++ +++ + -
‚Highly dense‘
0
25
50
75
Coverage of bare soil due to population types
p > 0.05
‚Transient‘ ‚Sparse‘ ‚Dense‘ ‚Highlydense‘
Invasive population types
Summary
• Population types
– A change in the life stage spectrum following
Invasion Optimum Regression
could not be proved
– Small individuals are dominant in all population types
• No correlation found between coverage of bare soil and population density or population structure, respectively
• With proceeding primary succession
– Decreasing population density
– Decreasing number of Small-Vegetative life stages
– Decreasing number of Seedlings/Juveniles
Conclusion
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
Thank you for your attention!
Best thanks to the colleagues of the Univ. of Innsbruck
Contact: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]: [email protected]
