Effect of mid-term drought on <i>Quercus pubescens</i> BVOC emissions seasonality and their dependence to light and/or temperature

Abstract. Biogenic volatile organic compounds (BVOC) emitted by plants are a large source of carbon compounds released into the atmosphere where they are precursors of ozone and secondary organic aerosols. Being directly involved in air pollution and indirectly in climate change, it is very important to understand what factors drive the BVOC emissions in order to characterize the atmospheric composition through models. The main algorithms currently used to predict BVOC emissions are mainly light and/or temperature dependent. Additional factors such as seasonality and drought have been also found to influence isoprene emissions, especially in Mediterranean region which is characterized by its drought period in summer. These factors are increasingly included in models but only for the principal studied BVOC which is isoprene but there are still some discrepancies in estimations of emissions. In this study, the main BVOC (isoprene, methanol, acetone, acetaldehyde, formaldehyde and MACR+MVK+ISOPOOH), emitted by Quercus pubescens a tolerant drought Mediterranean species, were monitored with a PTR-ToF-MS over an entire seasonal cycle, under both natural and amplified drought which is expected with climate change. Amplified drought impacted all BVOC by reducing emissions in spring and summer and, in the contrary, by increasing emissions in autumn. Two types of dependence were found: light and temperature dependence (isoprene, MACR+MVK+ISOPOOH and acetaldehyde), and light and temperature dependence during the day and only temperature dependence during the night (methanol, acetone and formaldehyde). Moreover, a methanol burst in early morning and formaldehyde deposition/uptake were also punctually observed which were not assessed by model.