Colonization, Survival and Competition of
Young Trees
Introduction I
Annual plants:
Life span: one growing season
Have to germinate, grow and bloom fast to produce seeds before the
end of growing season
Perennial plants:
Life span: two to more years
Plenty of resources: rapid growth
Few resources: efficient and low-loss growth
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Introduction II
Seasonal Adaptation of annual plants:
Alternation of growing season and dormant season
Preparations for dormant season:
Shedding the frost-sensitive parts
Frost-hardening persistent parts
Forming buds for the following season
Storing energy for winter and
budding in spring
Picture 1: Life cycle of perennial plants
-> Seasonal changes are controlled by hormonal changes
Abscisin acid: Supresses budding in dormant season
Gibberelin acid: Stimulates budding in growing season
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Introduction III
Plant growth in areas with only 1-3% light irradiation (Mittelland)
depends on different factors:
Carbon balance has to be positive over the year
Root formation has to be sufficient for water and nutrient intake
Frost-hardy has to be persistent enough before winter
Budding and formation of leaves in spring has to be ensured
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Introduction IV
Dynamics in forest gaps:
Light irradiation changes due to fires, storms or cultivation
Small gaps: 5-15% light, large gaps: 20-60% light
Plants grow faster and light-requiring species colonize gaps
Competition for light and nutrients -> selection for fast growing plants
Colonisation of gaps by:
Seeds capable of flight
Germ buds in the soil from previous seasons
Dominance of certain species dependent on:
Number of seeds
Rate of germination
Rate of vertical growth
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Introduction V
Most abundant trees in the Swiss Mittelland:
Shady areas:
Fagus sylvaticus (Rotbuche): very shade tolerant, survives with less than 5%
light
Cold, humid and disturbed areas (many storms, avalanches)
Acer pseudoplatanus (Bergahorn)
Fraxinus excelsior (Esche)
Assumption: Ash and Acer colonise areas with light faster than Beech. Beech
recaptures once the conditions are in its favour.
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Method I
 The length grow during over one year were
measured in six plants
 Only Beech and Ash were examined
Pictures:
2 Left: Fagus sylvatica
3 Right: Fraxinus excelsior
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Method II
 Measuring length growth of one year by
examining cicatrices (Narben) on terminal
buds on six plants
 Noting if there is browsing (Verbiss) of the
main shoot
 Determination of age of other plants
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Picture 4:
Terminal bud of Fraxinus
excelsior
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Method II
 Documentation: One mark per plant and year
Results I
What type of age distribution do the pouplations have?
Total plants in gap:
Beech (blue) 59
Ash (red)
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Results II
Age Distribution of a Gap in 2012
Age structure of young trees in a woodland gap (March 2012)
Number of trees (per 4 m2)
35
30
25
20
Beech
Esche
Ahorn
15
10
5
0
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
Year of germination
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Results III
Growth of Seedlings over Time
Tree height versus shoot growth in 2012 (ash - red; beech - blue)
50
45
R² = 0.45
R² = 0.6
40
Ash
Shoor growth in 2012
35
30
Beech
25
20
15
10
5
0
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0
20
40
60
80
100
Height (cm)
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120
140
160
180
200
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Results IV
Browsing:
Mean:
Beech: 0.72
Ash: 1.65
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Interpretation I
 Ash populates a newly formed gap faster due to high
germination rates and faster growth, even though it is browsed
more often.
 Beech is better adapted to sites with low light and will probably
recapture the area.
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Sources
 Picture 2: Fagus sylvatica
http://flora.nhm-wien.ac.at/Seiten-Arten/Fagus-sylvatica.htm last vistited on
26.5.2013.
 Picture 3: Fraxinus excelsior
http://www.botanik.de/bild/fraxinus-excelsior-gemeine-esche.html , last
visited on 26.5.2013.
 Picture 4: Terminal bud of Fraxinus excelsior
http://www.uni-graz.at/walter.obermayer/plants-of-styria/images/fraxinusexcelsior.html