Climatic conditions and concentrations of carbon dioxide and air pollutants during 'ESPACE-wheat' experiments

A major objective of the ESPACE-wheat programme was to perform by means of open-top chambers (OTCs) 'standardised' experimental investigations of spring wheat responses to increased atmospheric CO2 and O-3 concentrations and to other environmental stresses at different locations in Europe, representing a broad range of different climatic conditions. From 1994 to 1996 a total number of 25 OTC experiments were carried out. In addition, four growth chamber experiments focusing on key physiological processes of wheat growth in CO2-enriched air were performed. According to the specific needs for subsequent modelling purposes, environmental data were collected during experiments, i.e. air temperature, global radiation, humidity and trace gas concentrations. In the present paper results of these measurements are summarised. It was shown, that the OTC-experiments covered a considerable range of growing season mean-air-temperatures (13.0-23.4 degrees C) and global irradiances (10.8-18.1 MJ m(-2) d(-1)), the most important driving variables for crop growth simulation models. Mean concentrations of CO2 and O-3 in ambient air and in different treatments illustrated the observed variability of trace gas exposures between different experiments. Implications for subsequent analyses of biological response data are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.