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Theses, dissertations and research publications (including journal articles, conference abstracts and books) from Lund University are collected in this database. Where possible, the option to download a full text document is available. It is also possible to search for Lund University student theses in the student theses database.
| Title | Spatial and temporal dynamics of subarctic birch forest carbon exchange |
| Author/s | Michal Heliasz |
| Department/s |
Dept of Physical Geography and Ecosystem Science
|
| Full-text | Full text is not available in this archive |
| Defence date | 2012-06-11 |
| Defence time | 10:00 |
| Defence place | salen Världen, Geocentrum I, Sölvegatan 10, Lund |
| Opponent | Professor Timo Vesala |
| Publishing year | 2012 |
| Pages | 132 |
| Document type | Dissertation |
| Language | English |
| Publisher | Department of Physical Geography and Ecosystems Science, Lund University |
| Popular science abstract English |
The long-term stability of the global terrestrial carbon sink has been a matter of concern in that a weakening would have serious consequences for atmospheric CO2 concentrations and, hence, for further changes in climate. High northern latitudes are of special importance for the global carbon budget as they store large amounts of organic matter in the soil and are expected to be the most strongly affected by climate change. Here we investigate carbon exchange in the subarctic mountain birch forest growing on the limit where tree growth is possible. The study sites are located close to the Abisko village in northern Sweden, in the catchment of Lake Torneträsk. The investigated area is under influence of increasing temperature and periodical insect outbreaks causing defoliation of the trees. The last insect outbreak which has happened in 2004 caused at least 90 g C m-2 loss of carbon to the atmosphere and it turned the site from being carbon neutral in undisturbed years into a source of carbon. The forest was regenerating for 1-3 years after disturbances depending on the level of defoliation during outbreak. The annual carbon uptake in the undisturbed forest was mainly dependent on the length of the growing season and the amount of incoming light used for photosynthesis. Climate change causes an increase in the length of the growing season and expansion of the forest on tundra-heath ecosystem. The total annual loss of carbon by the forest to the atmosphere is mainly dependent on the thickness of the organic soil layer and temperature. Thickness of the organic soil in the forest is most likely connected with past transformation from a tundra-heath to the forest ecosystem. Loss of carbon in the tundra-heath ecosystem is limited by difficult to decompose carbon (carbon limitation) and expansion of birch with litter rich in easy to decompose carbon cause the newly established forest to be carbon source to the atmosphere. This study suggests that the invasion of deciduous tree species onto the carbon limited arctic tundra may cause high losses of soil carbon to the atmosphere. |
| Abstract English |
High northern latitudes are of special importance for the global carbon budget as they store large amounts of organic matter in the soil and are expected to be the most strongly affected by climate change. Here we investigate carbon exchange in the subarctic mountain birch forest growing on the limit where tree growth is possible. The study sites are located close to the Abisko village in northern Sweden, in the catchment of Lake Torneträsk. The investigated area is under influence of increasing temperature and periodical insect outbreaks causing defoliation of the trees. The last insect outbreak which has happened in 2004 caused at least 90 g C m-2 loss of carbon to the atmosphere and it turned the site from being C neutral in undisturbed years into a source of carbon. The forest was regenerating for 1-3 years after disturbances depending on the level of defoliation during outbreak. The annual cumulative gross primary production in the undisturbed forest was mainly dependent on the length of the growing season and the incoming radiation. Climate change causes an increase in the length of the growing season and expansion of the forest on tundra-heath ecosystem. The annual cumulative respiration is mainly dependent on the thickness of the organic soil layer and temperature. Thickness of the organic soil in the forest is most likely connected with past transformation from a tundra-heath to the forest ecosystem. Respiration in the tundra-heath ecosystem is carbon limited and expansion of birch with litter rich in highly labile carbon cause the newly established forest to be carbon source to the atmosphere. This study suggests that the invasion of deciduous tree species onto the C limited arctic tundra may cause high losses of soil carbon to the atmosphere. |
| Subject |
Earth and Environmental Sciences |
| Keywords | eddy covariance, mountain birch, carbon budget, insect outbreak, forest expansion, temporal variability, spatial variability |
| ISBN/ISSN/Other |
ISBN: 978-91-85793-27-3 |
| Supervisor | Torben Christensen |
| Funder |
VR |
| Funder |
FORMAS |
| Funder |
European Union |
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