Das Projekt "PO3PLAR" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. The over all objective of PO3PLAR is to complement the Level II ozone injury assessment program of the ICP-Forests WG on Ambient Air Quality with a well known and already investigated ozone sensitive bio-indicator species such a Populus spp. A successful establishment of the indicated bio-indicator on the Light Exposed Sampling Sites (LESS; see Manual for Assessment of Ozone Injury) will allow us to collect additional data on plant responses to ambient ozone concentrations on the very same species and variety across Europe. Excluding the disturbing factor of differing species composition of forest ecosystems and differing species specific responses to ozone (under the given microclimatic conditions) a harmonized bio-indicator network may allow us to gain additional valuable information to be implemented in regional as well as European efforts on ozone risk assessment. The 2007 season will serve as a test phase providing the participating countries to gain experience with the optimal planting procedure (soil, water availability, growth rate, etc.) hopefully leading to first successful phenological and physiological measurements and observations throughout the 2007 season. Currently the following 12 countries are participating in the PO3PLAR bio-indicator survey: Spain, Italy, France, Lithuania, Hungary, Germany, Sweden, Czech Republic, Cyprus, Belgium, USA and Switzerland whereas Switzerland is serving as the coordinator and data manager. From an organizational point of view, this project is not an official part of the ozone injury assessment program of the ICP-Forests WG on Ambient Air Quality. However, if successful we may be able to attract more interest in the respective community and hopefully generate some funding in the near future.