| 1. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 2. |
- Walker, M. D., et al.
(författare)
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Plant community responses to experimental warming across the tundra biome
- 2006
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 103:5, s. 1342-1346
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Tidskriftsartikel (refereegranskat)abstract
- Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, including warming; however, most studies were limited to a single location and were of short duration and based on a variety of experimental designs. In addition, comparisons among studies are difficult because a variety of techniques have been used to achieve experimental warming and different measurements have been used to assess responses. We used metaanalysis on plant community measurements from standardized warming experiments at 11 locations across the tundra biome involved in the International Tundra Experiment. The passive warming treatment increased plant-level air temperature by 1-3 degrees C, which is in the range of predicted and observed warming for tundra regions. Responses were rapid and detected in whole plant communities after only two growing seasons. Overall, warming increased height and cover of deciduous shrubs and graminoids, decreased cover of mosses and lichens, and decreased species diversity and evenness. These results predict that warming will cause a decline in biodiversity across a wide variety of tundra, at least in the short term. They also provide rigorous experimental evidence that recently observed increases in shrub cover in many tundra regions are in response to climate warming. These changes have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere.
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| 3. |
- Rytzler, Johannes, 1976-, et al.
(författare)
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Didaktik as the contour and content of teacher education ways forward in thinking about teaching
- 2024
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Ingår i: Teacher Education and Its Discontents. - : Taylor and Francis. - 9781040127599 - 9781032721613 ; , s. 121-138
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter illustrates how conceptions from the German language tradition of Didaktik can contribute to a nuanced understanding of the pedagogy of teacher education. Using the general disappointment toward teacher education as a point of departure, we turn to Deborah Britzman who points out some key issues of teacher education that make it inept to deal with educational relations as uncertain and ethical activities. She identifies the primary problem as that teachers and students in teacher education are influenced by their own educational experience in ways that make it difficult to approach education and educational relations in productive ways. We begin with a discussion of how the content of the teacher education programs entails a pedagogical dilemma for both its students and teachers. Then we show how this dilemma can be acknowledged by recognizing and embracing the inherent pedagogy and Didaktik of teacher education. By problematizing the relationship between pedagogy and Didaktik, we show the importance of not letting them be separated, as that risks making Didaktik instrumental. Based on this reasoning, we take note of some conceptions from Didaktik that we believe maintain a basic pedagogical problem in focus and show how these perspectives are suitable to adopt, not only as content for teacher education but also as a pedagogical framework for teacher education in general. In conclusion, we offer a proposal on how a higher education pedagogy, with a firm base in Didaktik, can contribute to both listening to and meeting the existential journey of student teachers from student to teacher, as well as contributing with the necessary knowledge of Didaktik and a professional language that is fruitful for the prospective teacher.
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