Structure of Carbon Dioxide Exchange Processes Above a Spruce Forest

Several micrometeorological techniques,’such as the flux-gradient method or the eddy covariance technique, offer the potential to measure net fluxes of water vapor, CO2 and other trace gases exchanged between ecosystems and the atmosphere (e.g., Baldocchi and Meyers 1998). Subsequent data analyses allow the calculation of net ecosystem CO2 exchange. These net fluxes, however, reflect the balance between different component fluxes. In the case of CO2, two opposing fluxes contribute to this net flux: CO2 uptake during photosynthesis and CO2 release during respiration from above- and belowground organisms. Distinguishing among these components is critical to obtain insights into the processes underlying ecosystem responses to climate forcing (Buchmann 2002). This is because environmental parameters, such as temperature and soil moisture, differentially affect biological activities (e.g., Baldocchi et al. 2001).