Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

Abstract

Abstract. Soil is a major contributor to the biosphereatmosphere exchange of carbonyl sulfide (COS) and carbon monoxide (CO). COS is a tracer with which to quantify terrestrial photosynthesis based on the coupled leaf uptake of COS and CO 2 , but such use requires separating soil COS flux, which is unrelated to photosynthesis, from ecosystem COS uptake. For CO, soil is a significant natural sink that influences the tropospheric CO budget. In the boreal forest, magnitudes and variabilities of soil COS and CO fluxes remain poorly understood. We measured hourly soil fluxes of COS, CO, and CO 2 over the 2015 late growing season (July to November) in a Scots pine forest in Hyytiälä, Finland. The soil acted as a net sink of COS and CO, with average uptake rates around 3 pmol m −2 s −1 for COS and 1 nmol m −2 s −1 for CO. Soil respiration showed seasonal dynamics controlled by soil temperature, peaking at around 4 µmol m −2 s −1 in late August and September and dropping to 1-2 µmol m −2 s −1 in October. In contrast, seasonal variations of COS and CO fluxes were weak and mainly driven by soil moisture changes through diffusion limitation. COS and CO fluxes did not appear to respond to temperature variation, although they both correlated well with soil respiration in specific temperature bins. However, COS : CO 2 and CO : CO 2 flux ratios increased with temperature, suggesting possible shifts in active COS-and CO-consuming microbial groups. Our results show that soil COS and CO fluxes do not have strong variations over the late growing season in this boreal forest and can be represented with the fluxes during the photosynthetically most active period. Well-characterized and relatively invariant soil COS fluxes strengthen the case for using COS as a photosynthetic tracer in boreal forests.

Soil–atmosphere exchange of carbonyl sulfide in a Mediterranean citrus orchard

“…Soil temperatures did change over the daily cycle (e.g., 26.0 to 42.4 • C at the BR site during summer), although such changes are still smaller than the seasonal changes in soil temperature (e.g., 10.5 to 31.8 • C at the BR site). A dominant role of soil moisture in explaining the variations in COS uptake is consistent with the results of Van Diest and Kesselmeier (2008) but less so with the negligible θ effects in grassland under simulated drought (Kitz et al, 2017).…”

“…The drivers of soil COS production are still unclear. COS could be produced by chemical processes in the lab (Ferm, 1957) but can also be produced by biotic process in soils such as hydrolysis of metallic thiocyanates (Katayama et al, 1992) with thiocyanate hydrolase (Conrad, 1996;Svoronos and Bruno, 2002) and hydrolysis of CS 2 (Cox et al, 2013;Smith and Kelly, 1988). Fungi are also reported to be the source of COS (Masaki et al, 2016).…”

“…Soil COS exchange has often been measured by incubations in the lab (e.g., Bunk et al, 2017;Kesselmeier et al, 1999;Liu et al, 2010;Van Diest and Kesselmeier, 2008), by static or dynamic chambers in the field (e.g., Berkelhammer et al, 2014;Kitz et al, 2017;Sun et al, 2018;Yi et al, 2007;Mseyk et al, 2014) and using models (e.g., Ogée et al, 2016;Sun et al, 2015;Whelan et al, 2016). In spite of these efforts, more field measurements of soil COS exchange are clearly needed as a basis for elucidating underlying mechanisms, as well as obtaining a better quantitative record of the possible range of soil COS fluxes under natural conditions.…”

“…In spite of these efforts, more field measurements of soil COS exchange are clearly needed as a basis for elucidating underlying mechanisms, as well as obtaining a better quantitative record of the possible range of soil COS fluxes under natural conditions. Note also that previous studies have focused on agricultural soils (Maseyk et al, 2014), wetlands (Whelan et al, 2013), boreal forest soils (Sun et al, 2018) and grasslands (Kitz et al, 2017), but several ecosystems are understudied, such as in those the Mediterranean. Finally, soil profile measurements will also be useful for the validation of soil models of COS exchange (Sun et al, 2015).…”

The Impact of Criteria Air Pollutants on Soil and Water: A Review

“…Particularly the depth of these two layers are the main reason that effects the rates of uptake by temperate soils [37]. This is also supported by a study conducted by Sun et al [38], according to which soil is considered as an important natural sink for CO and is hence known to be causing an influence on the tropospheric CO budget. However, the variabilities and magnitudes remain uncertain as of now.…”