FACE is the acronym of "free-air CO₂ enrichment", which is an experimental technique to study terrestrial ecosystems under elevated atmospheric CO₂ concentration. In FACE, CO₂ is released into the open air to raise the CO₂ concentration around a plant canopy without any enclosures, such as plastic covers. FACE enables studies of intact ecosystems under elevated CO₂ concentration, whereas studies with other methods can only be done on ecosystems detached and placed in the enclosures, such as greenhouses or controlled chambers. Due to this clear advantage of FACE over the enclosure methods, there are increasing number of FACE experiments set up in various ecosystems around the world. An overview of the FACE and related studies are given in Norby et al. (2001)¹⁾, and a list of the FACE projects is posted at the URL: http://public.ornl.gov/face/index.shtml (URL was moved May, 2011).

To review technological and scientific advances of the FACE projects around the world, we held the FACE 2000 international conference at the Tsukuba International Congress Center from June 27 to 30, 2000. The conference was planned to coincide with the final year of the Rice FACE project, which was conducted from 1996 through 2000 under the CREST (Core Research for Evolutional Science and Technology) scheme of Japan Science and Technology Corporation (JST). Preceding the conference, the participants visited the FACE site in Shizukuishi, Iwate Prefecture, and observed the on-going FACE experiment of its final season ( Photo 1 ). Support to the conference was given by JST, NIAES and other research organizations.

Major topics of the conference included FACE technologies, responses of various types of vegetation and ecosystems to increasing atmospheric CO₂, and integration across the vegetation types as well as process-based modeling of the vegetation responses. The conference had participants from 14 out of 17 FACE projects around the world, and the participants numbered 107 in all, of which 72 were from Japan, 16 from the USA, 6 from Australia, and 1-2 each from 11 countries in Europe, Asia and South America. Among the FACE projects represented in the conference, the FACE in Arizona, USA and Shizukuishi, Japan studied annual crops (wheat and rice, respectively), those in Switzerland and New Zealand conduced FACE on pastures, and the US FACEs except that in Arizona studied trees and natural vegetation. With the annual crops, a FACE experiment can easily cover a whole life cycle of the crop species, whereas, with perennial species such as trees, a few years of FACE covers only a fraction of the life span of the plant species. The FACE results should therefore be interpreted differently among the experiments with different species and ecosystems. There are, however, common features, such as stimulated photosynthesis, in the plant and ecosystems in their responses to elevated CO₂ concentration. To address both differences and similarities between ecosystems, the FACE 2000 Conference had sessions by vegetation types and sessions for synthesizing across them. In the former sessions, findings in FACE were reported and discussed within each vegetation type, whereas, in the latter ones, the FACE findings in various vegetation types were synthesized by each aspect of the ecosystem responses, such as photosynthesis and water relations.

The FACE 2000 Conference inspired communications among the FACE projects around the world, and led to the publication of the special issue, "Rising CO₂- future ecosystems", of an international journal, New Phytologist (Vol. 150, No. 2), whose cover page shows the FACE site in Shizukuishi. Many papers in the volume were the outcomes of the conference. As another outcome of the conference, a review of the FACE results on agricultural crops will be published in Advances in Agronomy (Kimball et al., 2002)²⁾. The conference was thus very much productive.