Reliability, CO{sub 2} concentration control, and CO{sub 2} gas use of the FACE facility at ETH in 1993 and 1994

Free-Air Carbon dioxide Enrichment (FACE) is one technique of many used to assess the effects of elevated concentrations of CO{sub 2} on plant communities. One primary advantage of FACE techniques is that they provide fumigation over large areas under essentially normal conditions compared to other techniques such as greenhouses, open-top chambers, etc. The FACE design developed by Brookhaven National Laboratory (BNL) is distinguished from other free-air designs by the introduction of a pre-diluted fumigation gas only at the periphery of an experimental plot and by relatively rapid, closed-loop control of treatment level based on gas concentration, wind speed, and wind direction. This report presents preliminary results concerning facility performance during 1993 and 1994 within three treatment arrays during FACE operations at the Eschikon Experimental Station of the Swiss Federal Institute of Technology, Institute for Plant Sciences, Zurich, Switzerland. The report includes summaries of data describing system reliability, temporal concentration control, spatial concentration control, C0{sub 2} use, and ambient C0{sub 2} concentrations.