Biogenic volatile organic compounds emitted by European Temperate forests: How do broadleaf species react to frost and drought?

Abstract

Biogenic volatile organic compounds (BVOCs) are a highly complex and diverse set of chemicals emitted into the atmosphere by the Earth's biosphere [1]. Atmospheric oxidation of BVOCs affects atmospheric mixing ratios of CH4, CO, and tropospheric O3, and leads to the formation of Secondary Organic Aerosol (SOA) (i.e., submicron particulate matter). Atmospheric aerosol plays a crucial role in defining Earth's radiative balance and impacts air-quality [2]. Climate models project a further increase in the average global temperature for the next decades. Warm winters appear to lead to earlier leaf-out which may put trees at higher risks of late frost in spring and summer droughts are increasing in frequency and extent. The probability that a late frost and an extreme summer drought occurs in the same year is expected to increase and thus, how trees respond to and recover from the (double) stress will be important in determining changes in BVOC emissions composition and quantities. Climate warming may thus lead to changes in atmospheric chemistry, including SOA properties [3]. During 2022, we studied the impact of spring frost and summer drought on BVOC emissions from broadleaf seedlings. We exposed 2-year-old seedlings of 3 species (Quercus petraea, Quercus robur, Fagus sylvatica) to an artificial spring frost by keeping seedlings with leaves that were fully out at -5.5℃ for 3 hours at the beginning of May 2022. Subsequently we simulated a summer drought from early July through the end of August (50% water reduction). The BVOC emissions of QP, QR, and FS, were measured deploying a PTR-ToF-MS alongside a newly developed plant chamber system [4] in August 2022. We address the following research questions in our conference contribution:  How do BVOC emissions composition and quantities of broadleaf control trees (QP, QR, FS) compare to coniferous ones (studied during AccliMemo 2022 [4])? How are the BVOC emissions of QP and FS modulated in response to a) late spring frost, b) summer drought,  and c) double stress?