Free-air concentration enrichment
Free Air Carbon Dioxide Enrichment or shortly FACE is a technical test setup, which allows the rising concentration of carbon dioxide in the atmosphere to simulate (the main cause of global warming ) in the field and to examine their influence on plants and ecosystems. By 2006 there were 32 FACE plants worldwide, the distributed equally between natural and artificial ecosystems.
Technology
Most FACE systems are based on at Brookhaven National Laboratory ( BNL ) developed technique: In the sample plots of vertical pipes with nozzles are mounted in an annular arrangement, from which carbon dioxide can be released. These devices are small plastic tubes to higher towers, since they are always much higher than the vegetation. They take up little space, so that the micro-climate (wind, solar radiation, evaporation) is not affected. From the tubes is blown, depending on wind direction and strength of carbon dioxide. Within the experimental area this results in a predefined carbon dioxide. This can be a fixed amount above the normal concentration (usually 200 ppm ) may be, but usually it is a fixed value that is depending on the test 475-660 ppm. These are values that are expected for mid / end of the 21st century. The test surface has a diameter of 1 to 30 meters, but usually about 10 m. In some systems, the ozone concentration is increased as a further component.
The advantage of the FACE plants compared to the older technology of the Open Top Chambers (CO2 in plastic containers ) is that they do not alter the microclimate, which is greatly influenced by OTCs (higher temperature, less wind, generally less stress on the plants ).
Technical disadvantages of the FACE system are: the increase of carbon dioxide concentration occurs abruptly, possibly leading to artifacts in comparison to the actual, slow rise; the carbon dioxide concentration varies with high frequency ( seconds to minutes); the experimental area is a maximum of 450 square meters, which is about 100 pine trees, for the influence of large herbivores or predators is too small; under very stable and windless conditions changed FACE microclimate easily.
In addition to the BNL - type, there are some different forms, such as a ring on the vegetation cover, from which the CO2 is discharged, or a network of narrow tubes that run within the tree crowns (web -FACE ).
FACE systems
The first FACE was from 1992 in Maricopa, Arizona, where for 10 years cotton, wheat and sorghum were grown. Other food crops, that have been investigated in various FACE are soya, corn, rice, potato. In Switzerland 10 years of economic Prairie was ( Lolium perenne and Trifolium repens ) gassed in a facility of ETH Zurich, in later launched FACE in New Zealand grasslands was grazed by sheep.
The mid-1990s also FACE systems have been built for forest plantations, for example for poplar (Italy ) or the American sweetgum. The state of Hesse promotes a project of the Geisenheim Research Institute in specialty crops with a unique start-up funding of one million euros for the years 2009 to 2011.
Documents
- George R. Hendrey, Francesco Miglietta: FACE Technology: Past, Present, and Future. In: J. Nösberger, S. P. Long, R. J. Norby, M. Stitt, G. R. Hendrey, H. Blum ( Ed.): Managed Ecosystems and CO2. Case Studies, Processes, and Perspectives. Ecological Studies, Vol 187 Springer -Verlag, Berlin, Heidelberg, 2006, pp. 15-43. ISBN 3-540-31236-6