Download Population structure of Artemisia genipi in a glacier

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