Ph.D. on Ecosystem-atmosphere exchange of carbon in a heath land under future climatic conditions

This Ph.D. was started September 2005 with Ph.D. student Merete Bang Petersen. The project focuses on carbon cycling in the ecosystem. The project will have its main activity within WP4, but includes elements of WP2 and 3 as well.

Background
During the past decades the atmospheric content of carbon dioxide (CO₂) has increased by ca. 25 %, and this increase is anticipated to continue due to increased fossil fuel usage. This, in combination with increases in other atmospheric greenhouse gases, is expected to induce a 2-4^oC increase in temperature as well as changes in precipitation patterns. Such changes in environmental conditions are expected to significantly alter the carbon cycling and -balance in terrestrial ecosystems with possible feed-back consequences for the atmospheric CO₂ chemistry, and for system nutrient cycling with implications for the biological and chemical functions. There is thus a need to achieve more knowledge on the coupling between climatic change and ecosystem C-cycling in order to better understand and predict possible feed-back mechanisms. The role of terrestrial ecosystems as CO₂ “sinks” has accordingly received much attention over the past years.

Content of the project
Field work takes place at the CLIMAITE FACE site in order to assess how future climatic and environmental conditions (increased CO₂, increased temperature and dry summer) influences the “whole-ecosystem” flux of CO₂. Flux chamber measurements are carried out regularly throughout the year to evaluate net ecosystem CO₂-fluxes, in combination with intensive campaigns to evaluate diurnal variability. The chamber flux measurements may also include other biogenic greenhouse gases such as nitrous oxide (N₂O) and methane (CH₄). The field-work will include assessments of the ”iso-flux” in which the ¹³C- and ¹⁸O-isotopes in evolved CO₂ is determined to differentiate heterotrophic and autotrophic activity. The isotopic work is combined with detailed process studies in the laboratory by the use of ¹³C-pulse labelling.