Trace gas exchange over terrestrial ecosystems: methods and perspectives in micrometeorology

Quantification of the surface-atmosphere exchange of trace gases is recognized as an essential prerequisite to understanding the role of the biosphere in the global climate system. Among the micrometeorological methods available to measure surface-atmosphere fluxes, the aerodynamic gradient, the energy balance/Bowen ratio, the eddy covariance and the eddy accumulation methods are the most widely employed. This brief review describes the theoretical background and the practical applications of these methodologies and is particularly directed to plant ecophysiologists, ecologists and botanists who may be interested in scaling biological processes to the canopy level.