25 years of atmospheric and ecosystem measurements in a boreal forest—Seasonal variation and responses to warm and dry years

摘要: Boreal forests make up 27% of the world’s forest landscape (FAO, 2020) and are an important source of trace gases and aerosols, releasing about 10% of the global biogenic volatile organic compound (BVOC) budget (Guenther 2013), and contributing 12–50% of the local atmospheric aerosol mass over Fennoscandia (Tunved et al. 2008). Furthermore, the boreal forest plant biomass is an important carbon sink, constituting> 25% of the global terrestrial carbon sink (Tagesson et al. 2020). Terrestrial ecosystems, such as boreal forests, form a strongly interconnected coupled system with the atmosphere. The boreal ecosystem continuously fixes atmospheric carbon and emits carbon to the atmosphere through photosynthesis and respiration, respectively, and emits BVOCs during, eg, plant growth and reproduction, and organic matter decomposition (eg, Hakola et al. 2017, Mäki et al. 2019). Biogenic and anthropogenic volatile organic compounds (VOCs) are highly susceptible to oxidation reactions involving hydroxyl and nitrate radicals as well as ozone in the atmosphere (Schulze et al. 2017). Monoterpenes emitted by the forest ecosystem, for instance, produce highly oxygenated organic molecules (HOMs) in the atmosphere (Ehn et al. 2014, Bianchi et al. 2019). HOMs can in turn contribute to the formation of atmospheric aerosol particles by clustering with other gasphase molecules, or by condensing onto a preexisting atmospheric aerosol particle population (Mutzel et al. 2015, Bianchi et al. 2019). The formation of atmospheric aerosol particles through the clustering of gas-phase molecules is called new particle formation (NPF). NPF is the main …