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Colonization, Survival and Competition of Young Trees

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

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Colonization, Survival and Competition of Young Trees

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  1. Colonization, Survival and Competition of Young Trees

  2. 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 Ökologie A&T

  3. 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 -> Seasonal changes are controlled by hormonal changes • Abscisin acid: Supresses budding in dormant season • Gibberelin acid: Stimulates budding in growing season Picture 1: Life cycle of perennial plants Ökologie A&T

  4. 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 Ökologie A&T

  5. 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 Ökologie A&T

  6. 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. Departement/Institut/Gruppe

  7. 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 Ökologie A&T

  8. 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 Picture 4: Terminal bud of Fraxinus excelsior Ökologie A&T

  9. Method II • Documentation: One mark per plant and year

  10. Results I What type of age distribution do the pouplations have? Total plants in gap: Beech (blue) 59 Ash (red) 112 Ökologie A&T

  11. Results II Age Distribution of a Gap in 2012 Beech Ökologie A&T

  12. Results III Growth of Seedlings over Time Ash Beech Ökologie A&T

  13. Results IV Browsing: Mean: Beech: 0.72 Ash: 1.65 Ökologie A&T

  14. 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. Ökologie A&T

  15. Sources • Picture 2: Fagus sylvatica http://flora.nhm-wien.ac.at/Seiten-Arten/Fagus-sylvatica.htmlast 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/fraxinus-excelsior.html

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