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Title: Impacts of environmental change on subarctic dwarf shrub communities : landscape gradient and field manipulation approaches
Author: Koller, Eva Katharina
ISNI:       0000 0004 2720 9365
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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Global warming is predicted to be most severe at high latitudes, where cold-adapted ecosystems may be vulnerable to change and carbon-rich soils are a source of green- house gas emissions and positive feedback to climate. This makes ecological responses of arctic ecosystems to climate change a pressing concern. Usually, responses to climate change factors are addressed by short-term experimental manipulation, which can be misleading when trying to predict long-term responses. In this thesis, this was addressed by studying the growth responses of three ubiquitous subarctic dwarf shrubs to higher temperatures, earlier snow melt and higher nutrient availability using a combination of detailed study of an environmental gradient and long-term (18 years) field manipulation of temperature and nutrient availability. The most important findings were: i) Contrary to current opinion, delays in snow melt timing did not considerably affect dwarf shrub phenology, and the timing of leaf bud burst did not influence total summer shoot growth ii) Widespread P limitation (rather than N limitation) of growth was found in all studied species. This coincided with strong P immobilization in soils. Accordingly, soil P availability was strongly correlated with growth in deciduous shrubs. If climate change induces higher N mineralization, P may become limiting to plant growth and hence be more important than N in mediating arctic plant responses to global change iii) Leaf N and P per shoot were closely correlated with growth. In the deciduous species, there was more shoot growth per unit leaf N under warming, indicating that in a future, warmer climate, nutrient availability may have to increase by very little to increase productivity in deciduous shrubs. This provides insight into the mechanisms driving the increase in deciduous shrub abundance in arctic ecosystems in the last 50 years. This work suggests that further research on the arctic phosphorus cycle and its responses to climate change is urgently needed for better predictions of the response of arctic ecosystems to climate change.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available