Abstract
Climate is changing, and more adverse changes are expected in the future. Changes, caused by continuously rising atmospheric concentrations of greenhouse gasses as CO2, will affect ecosystem processes and functions in the future and hence the cycling of carbon. The vaste amount of studies have focused on effects of climate change on aboveground biomass, less have been conducted on belowground biomass, and the thesis is one of few studies comprising both above- and belowground biomass and take interactions of climate change factors into account.
To follow the fate of carbon in the ecosystem we used the stabile isotope 13C. We found that elevated CO2 increased enrichment of 13C in leaves and deep roots of the dominant grass Deschampsia flexuosa, and enhanced carbon cycling, while drought reduced 13C enrichment in top roots and moderated carbon cycling. Both elevated CO2 and drought led to proportional more carbon allocated to the deepest roots. Long term effects showed increased root biomass due to elevated atmospheric CO2, and the effects seemed to increase over time. However it was also evident that the effect size was dependent on sampling month. In contrast, aboveground biomass showed no persistent changes over the years. Responses of aboveground and belowground biomass were coupled, and Deschampsia flexuosa showed high ability to adapt to treatments.
As the major response was observed belowground, I further studied decomposition of fine roots. Fine roots of Deschampsia flexuosa from deep layers showed much slower decomposition than fine root from top layer. Higher roots biomass and allocation of carbon deeper down in the soil profile in response to elevated CO2 combined with the slower decomposition of deep roots could affect future carbon cycling, but soil carbon sequestration depends on the further fate of carbon in the rhizosphere.
To follow the fate of carbon in the ecosystem we used the stabile isotope 13C. We found that elevated CO2 increased enrichment of 13C in leaves and deep roots of the dominant grass Deschampsia flexuosa, and enhanced carbon cycling, while drought reduced 13C enrichment in top roots and moderated carbon cycling. Both elevated CO2 and drought led to proportional more carbon allocated to the deepest roots. Long term effects showed increased root biomass due to elevated atmospheric CO2, and the effects seemed to increase over time. However it was also evident that the effect size was dependent on sampling month. In contrast, aboveground biomass showed no persistent changes over the years. Responses of aboveground and belowground biomass were coupled, and Deschampsia flexuosa showed high ability to adapt to treatments.
As the major response was observed belowground, I further studied decomposition of fine roots. Fine roots of Deschampsia flexuosa from deep layers showed much slower decomposition than fine root from top layer. Higher roots biomass and allocation of carbon deeper down in the soil profile in response to elevated CO2 combined with the slower decomposition of deep roots could affect future carbon cycling, but soil carbon sequestration depends on the further fate of carbon in the rhizosphere.
| Original language | English |
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| Publisher | Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen |
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| Number of pages | 131 |
| Publication status | Published - 2016 |
