Volatile emissions from thawing permafrost soils are influenced by meltwater drainage conditions

Abstract

Vast amounts of carbon are bound in both active layer and permafrost soils in the Arctic. As a consequence of climate warming, the depth of the active layer is increasing in size and permafrost soils are thawing. We hypothesize that pulses of biogenic volatile organic compounds are released from the near‐surface active layer during spring, and during late summer season from thawing permafrost, while the subsequent biogeochemical processes occurring in thawed soils also lead to emissions. Biogenic volatile organic compounds are reactive gases that have both negative and positive climate forcing impacts when introduced to the Arctic atmosphere, and the knowledge of their emission magnitude and pattern is necessary to construct reliable climate models. However, it is unclear how different ecosystems and environmental factors such as drainage conditions upon permafrost thaw affect the emission and compound composition. Here we show that incubations of frozen B horizon of the active layer and permafrost soils collected from a High Arctic heath and fen release a range of biogenic volatile organic compounds upon thaw and during subsequent incubation experiments at temperatures of 10°C and 20°C. Meltwater drainage in the fen soils increased emission rates nine times, while having no effect in the drier heath soils. Emissions generally increased with temperature, and emission profiles for the fen soils were dominated by benzenoids and alkanes, while benzenoids, ketones, and alcohols dominated in heath soils. Our results emphasize that future changes affecting the drainage conditions of the Arctic tundra will have a large influence on volatile emissions from thawing permafrost soils – particularly in wetland/fen areas.

Process Understanding of Soil BVOC Fluxes in Natural Ecosystems: A Review

“…Furan and its derivatives can be formed in soils through oxidation by iron and hydrogen peroxide (Huber et al, ). Kramshøj et al () reported 2‐Methylfuran emissions from permafrost soils at 10 and 20 °C in laboratory incubations. Mancuso et al () reported methylfuran emissions from three different kinds of soils (one agricultural soil and two forest soils) under laboratory conditions.…”

“…Gas diffusion is often thought to be the main mechanism of gas transport in vadose zone. Kramshøj et al () found that drainage of meltwater from permafrost significantly increased BVOC emissions from fen soils and the authors attributed this phenomenon to the low diffusion rates in water‐logged soils.…”

“…An increase in soil moisture can increase microbial activity at low soil moisture content, resulting in an increase in soil BVOC uptake, but also in a decrease of the amount of gas accessible to soil microbes (Asensio, Peñuelas, Filella, et al, ; Cleveland & Yavitt, ). Once soils begin to turn anaerobic, a further increase in soil moisture may inhibit aerobic microbial activities (Kramshøj et al, ), while less‐efficient anaerobic microbes start to convert BVOCs to methane (CH 4 ). Furthermore, if soils encounter drought, a decrease in soil moisture can reduce microbial activities through cell desiccation, and hence, reduce uptake.…”

Volatile Organic Compound fluxes in a subarctic peatland and lake

“…Recently, arctic VOCs have received increased attention (e.g. Kramshøj et al, 2016Kramshøj et al, , 2018Kramshøj et al, , 2019 and this study is another contribution towards the understanding of VOC budgets in northern wetlands and inland waters.…”

“…Northern ecosystems are known to exchange climate-relevant trace gases with the atmosphere, not only long-lived greenhouse gases such as carbon dioxide (CO 2 ) or methane (CH 4 ) but also hundreds of different volatile organic compounds (VOCs) that are a highly reactive part of the carbon cycle (Rinnan et al, 2014). Trace gases originate from sources as diverse as soils, peats, vegetation and lakes, and currently several of them show a trend towards greater emission rates with climate warming (Kramshøj et al, 2019;Lindwall et al, 2016a;Wik et al, 2016). At the same time, the warming-induced expansion of woody shrubs into tundra ecosystems (Myers- Smith and Hik, 2018) could enhance the photosynthetic uptake of CO2 and offset concurrent increases in heterotrophic respiration (Mekonnen et al, 2018).…”