A micrometeorological technique for simultaneously measuring fluxes of carbon dioxide, water vapour, and energy (heat) above a plant canopy and hence the net exchange of carbon between an ecosystem and the atmosphere. It is now widely used in ecology, for example for determining the amounts of carbon dioxide that are absorbed or emitted by different types of vegetation cover and whether particular sites are sinks or sources of carbon. It involves the installation of a tower that reaches above the tallest vegetation (e.g. above the tree canopy) and carries sensitive monitoring instruments, notably an infrared gas analyser (to monitor carbon dioxide and water vapour concentrations) and an anemometer to detect temperature changes and measure the eddy currents created by the gas fluxes between the atmosphere and the site. Other meteorological data are also collected. Integration of these data shows the extent of carbon and energy fluxes due to photosynthesis and respiration of not just the vegetation but the entire ecological community at the site, including soil organisms. Monitoring can be performed continuously, creating a complete and accurate picture of the overall carbon budget for a site on a daily, monthly, or annual basis. If the chosen site is representative, the information it provides can be extrapolated over a much greater area. Such information is vital not only for estimating levels of productivity and studying other ecological aspects but also for constructing accurate models of how ecosystems interact with the climate and how this might affect weather patterns and climate change.
Subjects: Biological Sciences.