Carbon exchange of a recently harvested boreal Jack Pine stand

A clearcut harvested in August 2002 has been included as part of a chronosequence of jack pine sites aged 1, 9, 28 and 74 years respectively, to study the evolution of the ecosystem carbon budget typical for the boreal jack pine forest after harvest. The sites are part of the BERMS (Boreal Ecosystems Research and Monitoring Sites) project, studying the area 100 km north east of Prince Albert, Saskatchewan.

An eddy covariance system consisting of a CSAT3 sonic anemometer and an open path LI7500 IRGA was installed at the site in March 2003, followed by a closed path LI7000 in November 2003. A comparison of the data from the open and closed path systems will be presented, for the period from November 2003 to spring 2004

Ecosystem respiration, i.e., nighttime net ecosystem exchange (NEE), increased exponentially with soil temperature at 2 cm up to 15^oC and then plateaued. The level of the plateau varied from 1 to 2 μmol C m^-2 s^-1 depending on soil water content. Daytime NEE during the summer approached zero, indicating that some photosynthesis was present. The data were gap filled using a nighttime friction velocity threshold of 0.13 m s^-1 and annual fits for both the dependence of respiration on soil temperature and photosynthesis on photosynthetically active radiation. This led to a preliminary calculated annual NEE of 120 g C m^-2 (i.e., carbon loss) for the clearcut.