Transcript Age and size structure of Trifolium pallescens populations

15th annual meeting of the Section Plant Population Biologie of the Society for Ecology, May 2002
Longevity of seeds
in a glacier foreland
of the Central Alps
- a burial experiment
Erich Schwienbacher & Brigitta Erschbamer
Institute of Botany
University of Innsbruck
Contact: [email protected]
Introduction
 Seed germination:
important life history trait
 Seed banks:
important sources for the regeneration
Introduction
 Lack of knowledge about longevity of alpine seeds
• Controversial opinions about the glacier foreland
 burial experiment
Hypotheses
• persistence of seeds is dependent on size
(1) small seeds  long-lived
(2) big seeds  short-lived
• but independently of the size
(3) hard-coated seeds  long-lived
ROTMOOSFERNER
Tyrol, Austria
burial site
glacier foreland
2300 - 2400 m a.s.l.
46°49‘N 11°02‘E
Species used for the experiment
weight per 100 seeds [mg]
Saxifraga aizoides
Saxifraga oppositifolia
Linaria alpina
Achillea moschata
Artemisia genipi
Trifolium pallescens
Oxyria digyna
Geum reptans
Anthyllis alpestris
0
100
200
300
400
Types of seeds
• small
• big
5 mm
1 mm
Saxifraga aizoides
Anthyllis alpestris
• hard-coated
1 mm
Trifolium pallescens
Design of experiment
fresh
1-year
2-year
5-year
• 4 groups
• 9 species
• 100 seeds
• 5 replicates
Protocol of the burial experiment
and the germination test
fresh seeds
stratification (+ 4°C)
growth chamber: germination test - 100 days
germination rate
‚growth chamber‘
scarification of hard-coated seeds
growth chamber: germination test - 10 days
germination rate
‚scarified seeds‘
Protocol of the burial experiment
and the germination test
field experiment
fresh seeds
1-year burial
stratification
(+ 4°C)
stratification +
germination in the field
growth chamber: germination test - 100 days
germination rate
‚field‘
germination rate
‚growth chamber‘
scarification of hard-coated seeds
growth chamber: germination test - 10 days
germination rate
‚scarified seeds‘
Protocol of the burial experiment
and the germination test
field experiment
fresh seeds
stratification
(+ 4°C)
1-year burial
2-year burial
5-year burial
stratification + germination
in the field
growth chamber: germination test - 100 days
germination rate
‚field‘
germination rate
‚growth chamber‘
scarification of hard-coated seeds
growth chamber: germination test - 10 days
germination rate
‚scarified seeds‘
Results
germination rate [%]
• fresh seeds
100
Saxifraga aizoides
75
Artemisia genipi
50
Oxyria digyna
25
Anthyllis alpestris
0
0
25
50
time [days]
75
100
Results
• fresh seeds:
 high germination rates
(42.7 % ± 34.7)
• 1-year burial:
 mostly low germination rates
(10.6 % ± 13.8)
but: increasing germination rates
with increasing seed weight
Results
• 1-year burial
log no. of seedlings
Regression: seed weight/number of seedlings
2
.
0
R²=0.82
1
.
2
0
.
4
0
.
4
2
.
5
2
.
0
1
.
5
1
.
0
0
.
5
log seed weight
Results
hard-coated seeds:
Linaria alpina, Trifolium pallescens, Anthyllis alpestris
• 1-year burial
• fresh seeds
germination rate [%]
germination rate [%]
75
75
50
50
25
25
0
0
no scarification
scarification
no scarification
scarification
Conclusions
(1) hard-coated seeds
 potential to form persistent seed banks
(2) big seeds
 germinate after the first year in the field
(3) small seeds
 loose their viability during the first winter ?
or
 secondary dormancy takes place ?
Future
• For how long do seeds persist
in the glacier foreland?

• 2-year burial
• 5-year burial
Acknowledgements
• Jürg Stöcklin
• Colleagues of the Univ. Innsbruck
• Austrian Academy of Science
Thank you for your attention!
Contact: [email protected]