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Monoterpenes are major compounds emitted by plants and contribute to the formation of photochemical oxidants and secondary organic aerosols in the troposphere. We measured monoterpene emissions from Chamaecyparis obtusa, a major coniferous tree species in Japan, in both the field and the laboratory. Short-term monoterpene emission from C. obtusa was typically dependent on temperature but barely dependent on light intensity. We calculated the basal emission rate E s assuming β = 0.09 in the G93 model. Three individual trees showed similar, but large seasonal variations in E s ; e.g., 0.21-5.42 µg g DW -1 h -1 for a tree showing the highest emission rate. The emission rate was much higher in winter and autumn. Although E s values averaged over 4 seasons indicated that C. obtusa is an intermediate emitter among coniferous trees, our results suggest that the large seasonal variation in E s should be considered in estimating annual monoterpene emission from this species. Furthermore, we found a significant effect of branch-to-branch touching by vibration on monoterpene emission from this species, suggesting that wind effect should be considered in the future for more precise emission estimation.

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