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: erich.schwienbacher@uibk.ac.at

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: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.atContact: erich.schwienbacher@uibk.ac.at