Greenhouse gas flux monitoring in ecosystems is mostly conducted by closed chamber and eddy covariance techniques. To determine the relevance of the two methods in rice paddy fields at different growing stages, closed chamber (CC) and eddy covariance (EC) methods were used to measure the methane (CH4) fluxes in a flooded rice paddy field. Intensive monitoring using the CC method was conducted at 30, 60 and 90 days after transplanting (DAT) and after harvest (AHV). An EC tower was installed at the centre of the experimental site to provide continuous measurements during the rice cropping season. The CC method resulted in CH4 flux averages that were 58%, 81%, 94% and 57% higher than those measured by the EC method at 30, 60 and 90 DAT and after harvest (AHV), respectively. A footprint analysis showed that the area covered by the EC method in this study included non-homogeneous land use types. The different strengths and weaknesses of the CC and EC methods can complement each other, and the use of both methods together leads to a better understanding of CH4 emissions from paddy fields.

Gas-phase hydrogen peroxide (H 2 O 2 ) is very harmful to plants when combined with ozone (O 3 ). Information on ambient H 2 O 2 concentrations, especially for long durations, is limited not only in Thailand and South East Asia but also in Japan. The objective of the present research was to accumulate data of H 2 O 2 concentrations over long durations in Tokyo and Thailand. Hydrogen peroxide concentrations were monitored at

Index Terms-Carbon use efficiency, eddy covariance technique, first ratoon cane.

Crop response to future air pollution stress is important information for crop production in the future. Ozone (O 3) and peroxides are recognized as significantly damaging air pollutants to plants. Therefore, the present research aimed to investigate the single and combined effects of O 3 and peroxides on leaf injury and physiological responses, and to compare the soybean cultivar sensitivities under exposure to single O 3 and combined O 3 and peroxides. Two Japanese soybean cultivars, Tachinagaha (TC), and Chamame (CM) and two Thai soybeans, A75 and Sorjor 5 (SJ5) were selected as plant materials. Four treatment plots were set up, including a control plot (C plot: free O 3 and peroxides), O 3 50 ppbv (O plot), O 3 50 ppbv and peroxides 2-3 ppbv (OP1 plot) and O 3 50 ppbv and peroxides 4-5 ppbv (OP2 plot). We found that combined O 3 and several ppbv peroxides (OP2 plot) caused more severe damage than the OP1 plot and single O 3 (O plot) to leaf injury, chlorophyll content and photosynthetic rate, and reduced total dry weight and pod dry weight. In combined O 3 and peroxides exposure, SJ5 showed the most sensitive cultivar in leaf injury, photosynthetic rate, biomass and pod dry weight, while CM showed less sensitivity for photosynthetic rate and pod dry weight.

Air pollutant concentrations such as ozone (O 3 ) and peroxides have been increasing in the world, and may cause many negative impacts on crop production. The objectives of the present study are to investigate the effects of peroxides and O 3 on visible foliar injury and physiological responses, and to compare the sensitivities among two Thai rice cultivars, RD 31 and Chainat 1, and two Japanese rice cultivars, Nipponbare and Nourin 52, under exposure to single O 3 and combined O 3 and peroxides. Four treatment plots were prepared, namely control plot (O 3 2-3 ppbv and free peroxides), O 3 50 ppbv plot and free peroxides, O 3 50 ppbv and peroxides 3 ppbv plot and O 3 50 ppbv and peroxides 5 ppbv plot. The results showed that combined O 3 and several ppbv peroxides plots caused severe damage on visible leaf injury, increase in Malondialdehyde (MDA) concentration, and decrease in total chlorophyll content and a net photosynthetic rate much higher than single O 3 plot. According to the O 3 dose response analysis, we found that, in combined O 3 (50 ppbv) and peroxides (3 ppbv and 5 ppbv) exposure, in case of visible foliar injury, Chainat 1 was seriously damaged rice cultivar while Nipponbare was a less damaged rice cultivar.