Monoterpene emissions in response to long-term night-time warming, elevated CO_2 and extended summer drought in a temperate heath ecosystem

摘要

Monoterpenes emitted from plants have an important role in atmospheric chemistry through changing atmospheric oxidative capacity, forming new particles and secondary organic aerosols. The emission rates and patterns can be affected by changing climate. In this study, emission responses to six years of climatic manipulations (elevated CO_2, extended summer drought and night-time wanning) were investigated in a temperate semi-natural heath ecosystem. Samples for monoterpene analysis were collected in seven campaigns during an entire growing season (April-November, 2011). The results showed that the temperate heath ecosystem was a considerable source of monoterpenes to the atmosphere, with the emission averaged over the 8 month measurement period of 21.7 ± 6.8 μg m~(-2) ground area h~(-1) for the untreated heath. Altogether, 16 monoterpenes were detected, of which the most abundant were α-pinene, δ-3-carene and limonene. The emissions of these three compounds were positively correlated with light, chamber temperature and litter abundance, but negatively correlated with soil temperature. Elevated CO_2 tended to decrease the average monoterpene emissions by 40% over the whole growing season, and significantly reduced emissions in August. Extended summer drought significantly decreased the emission right after the drought treatment period, but also in the late growing season. Night-time warming significantly increased the total emissions (mainly a-pinene) in April, and tended to mitigate the decrease caused by drought. The inhibition effects of elevated CO_2 on emissions were diminished when the treatment was combined with drought or warming.