High performance of CO 2 –temperature gradient chamber newly built for studying the global warming effect on a plant population

To study the effect of global warming concomitant with rising CO 2 on plant growth under field‐like conditions, a CO 2 –temperature gradient chamber (CTGC) was created from a standard temperature gradient chamber (TGC). Despite great daily and seasonal changes in ambient air temperature, the gradient of air temperatures was simulated by 5°C warmed conditions at the air outlet, rising at a rate of 1°C at 5 m intervals. Also, CO 2 concentrations were linearly increased from the air inlet to the outlet; those at the air inlet and 25 m distance from the air inlet were 372 p.p.m and 756 p.p.m. (doubled), respectively. The CTGC proved successful in biological experiments conducted through a full growth season in 1998. This apparatus will be useful for understanding plant response to simultaneous changes in CO 2 and temperature. Being a combination of a TGC and a CO 2 gradient chamber, the improved CTGC allows parameters and validation data sets to both be obtained for models contributing to plant growth, species composition, and global carbon flux analysis.