Volatile organic compound fluxes in a subarctic peatland and lake

Abstract

Abstract. Ecosystems exchange climate-relevant trace gases with the atmosphere, including volatile organic compounds (VOCs) that are a small but highly reactive part of the carbon cycle. VOCs have important ecological functions and implications for atmospheric chemistry and climate. We measured the ecosystem-level surface–atmosphere VOC fluxes using the eddy covariance technique at a shallow subarctic lake and an adjacent graminoid-dominated fen in northern Sweden during two contrasting periods: the peak growing season (mid-July) and the senescent period post-growing season (September–October). In July, the fen was a net source of methanol, acetaldehyde, acetone, dimethyl sulfide, isoprene, and monoterpenes. All of these VOCs showed a diel cycle of emission with maxima around noon and isoprene dominated the fluxes (93±22 µmol m−2 d−1, mean ± SE). Isoprene emission was strongly stimulated by temperature and presented a steeper response to temperature (Q10=14.5) than that typically assumed in biogenic emission models, supporting the high temperature sensitivity of arctic vegetation. In September, net emissions of methanol and isoprene were drastically reduced, while acetaldehyde and acetone were deposited to the fen, with rates of up to -6.7±2.8 µmol m−2 d−1 for acetaldehyde. Remarkably, the lake was a sink for acetaldehyde and acetone during both periods, with average fluxes up to -19±1.3 µmol m−2 d−1 of acetone in July and up to -8.5±2.3 µmol m−2 d−1 of acetaldehyde in September. The deposition of both carbonyl compounds correlated with their atmospheric mixing ratios, with deposition velocities of -0.23±0.01 and -0.68±0.03 cm s−1 for acetone and acetaldehyde, respectively. Even though these VOC fluxes represented less than 0.5 % and less than 5 % of the CO2 and CH4 net carbon ecosystem exchange, respectively, VOCs alter the oxidation capacity of the atmosphere. Thus, understanding the response of their emissions to climate change is important for accurate prediction of the future climatic conditions in this rapidly warming area of the planet.

Separating direct and indirect effects of rising temperatures on biogenic volatile emissions in the Arctic

“… 43 ). Warming is highly relevant for tundra VOC emissions, which increase steeply with temperature above a minimum temperature of ∼10 °C ( 32 , 44 ). Furthermore, prolongation of the growing season due to warming not only extends the period of potentially high biological activity, but also leads to alterations in phenology and vegetation composition ( 42 , 45 ), which were accounted for in our simulations considering the indirect effects of warming.…”

Volatile organic compound emission in tundra shrubs – Dependence on species characteristics and the near-surface environment

“…We cannot elucidate whether part of the stress compounds were emitted in response to this particularly hot summer. It should also be noted that, as it was not possible to derive significant temperature response curves for all compound groups used in MEGAN, the modelled seasonal values in this study were based on the standard G93 temperature response curve ( Guenther et al, 1993 ), which may underestimate emissions as compared to using a temperature response curve derived from arctic species ( Tang et al, 2016 ; Seco et al, 2020 ).…”

Potential of Climate Change and Herbivory to Affect the Release and Atmospheric Reactions of BVOCs from Boreal and Subarctic Forests

“…These drivers will affect other drivers of warming, such as increased emissions of the greenhouse gas methane from the oceans [ 3 ] and thawing permafrost [ 4 , 5 , 6 ]. Emissions of biogenic volatile organic compounds (BVOC) are strongly temperature dependent with daily and annual variation of emission rates [ 7 ]. Thus, warming in the boreal and subarctic areas will also increase the emission rates of BVOCs from soil and vegetation, peatlands [ 7 , 8 ], and lake waters [ 7 ].…”

“…Emissions of biogenic volatile organic compounds (BVOC) are strongly temperature dependent with daily and annual variation of emission rates [ 7 ]. Thus, warming in the boreal and subarctic areas will also increase the emission rates of BVOCs from soil and vegetation, peatlands [ 7 , 8 ], and lake waters [ 7 ]. In forests, the foliage [ 9 ], trunks [ 10 ], cones [ 11 ], roots, and rhizosphere [ 12 , 13 ] of trees, leaf and needle litter deposited on soil [ 14 ] and tree stumps [ 15 ] can be sources of BVOCs.…”