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- Hytteborn, Håkan, et al.
(author)
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Century-long tree population dynamics in a deciduous forest stand in central Sweden
- 2017
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In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 28:5, s. 1057-1069
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Journal article (peer-reviewed)abstract
- Question: We quantify tree dynamics over a century of free development in a small broadleaved forest dominated by Fraxinus excelsior and Ulmus glabra. What are the internal and external factors driving the changes, and how predictable are they? What were the time scale and effects of the spread of Dutch elm disease (DED)? Location: Vårdsätra, eastern central Sweden.Methods: The survival, growth and recruitment of all trees (≥ 12 cm in girth) were monitored in 1912, 1967, 1988 and 2013 (more often for a part of the forest). Woody species in the field and shrub layers were surveyed in permanent plots in 1976 and 2012. We used transition matrix models to project changes in population sizes and species composition within the century and for 2050.Results: The results indicate that the forest was in a successional development during the first period. The species composition had stabilised by 1967, except for an expansion of Acer platanoides and the drastic effect of DED that struck the forest around 2000. It took only a decade to kill virtually all large elms in the forest, leading to strong decrease in stem density and basal area. The evidence for effects of DED is still weak, but there has been an increase in saplings, notably of Fraxinus, Prunus padus, Ulmus, and of shoots of Corylus avellana. Several species that are abundant in the vicinity and as seeds fail to establish (Picea abies, Betula spp., Quercus robur, Populus tremula). Projections for 2050 based on the third period (1988-2013) are probably unrealistic since also Fraxinus may disappear because of the recent arrival of the ash dieback.Conclusions: Slow dynamics in forests that could follow from climate change will locally probably be overruled by unforeseen catastrophes, such as invasions by forest pathogens. These initiate changes with long lag phases difficult to quantify. Still, a dense deciduous forest can resist invasion of colonist species and of regionally dominant conifers; the reason being unfavourable conditions for establishment rather than dispersal limitation
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| 2. |
- Magnusson, Andreas
(author)
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Från ett perspektiv på ekologiska processer till ett verktyg för att diskutera hållbarhetsfrågor : Hur ekosystemtjänster – ett nytt ämnesinnehåll, kan ta form i undervisningspraktiken
- 2017
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Licentiate thesis (other academic/artistic)abstract
- The aim of this study was to generate knowledge about how teachers embark on new subject content and how their understandings of ecosystem services evolve and change in teaching practice, and also what it means to be able to discuss the relationship between the ecological and social in terms of ecosystem services in a teaching practice in middle school.The teachers used the learning study model and variation theory to explore the object of learning, by trying to design an instruction that offers fifth grade students the possibility to develop their knowledge of ecosystem services. The learning study model is an interventionist approach, where the focus is on an object of learning. A group of teachers worked together and tested students, planned lessons and implemented, evaluated and refined the lessons in an iterative process.The theoretical framework, variation theory, is a theory of learning that focuses on how discernment of aspects affects the way we perceive our world and how variation can be used to promote learning. However, since the study aims at contributing to enhancing our knowledge of how teachers can develop their skills and their meanings of a new content in practice, the empirical data from learning study was then analyzed with the help of activity theory, and the cycle of expansive learning.The result of the study shows that it can be complicated to introduce a new educational content. However, the learning study model proved to be aneffective tool for developing teachers' knowledge of ecosystem services and how to teach this. Ecosystem services were developed as teachers worked systematically with the content in their practice. For example, when the students did not respond to the exercises and to the reasoning of the ecosystem services that the teachers had planned, contradictions were created and changed the learning object's meaning for the teachers. The recordings from the lessons made the contradictions that arose during the lesson visible. Ecosystem services were developed from being primarily a tool to describe the human needs of the non-human nature to a tool to be able to discuss sustainability issues and the relationship between ecological, economic and social dimensions.
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