In situ soil COS exchange of a temperate mountain grassland under simulated drought

Abstract

During recent years, carbonyl sulfide (COS), a trace gas with a similar diffusion pathway into leaves as carbon dioxide (CO2), but with no known “respiration-like” leaf source, has been discussed as a promising new approach for partitioning net ecosystem-scale CO2 fluxes into photosynthesis and respiration. The utility of COS for flux partitioning at the ecosystem scale critically depends on the understanding of non-leaf sources and sinks of COS. This study assessed the contribution of the soil to ecosystem-scale COS fluxes under simulated drought conditions at temperate grassland in the Central Alps. We used transparent steady-state flow-through chambers connected to a quantum cascade laser spectrometer to measure the COS and CO2 gas exchange between the soil surface and the atmosphere. Soils were a source of COS during the day, emissions being mainly driven by incoming solar radiation and to a lesser degree soil temperature. Soil water content had a negligible influence on soil COS exchange and thus the drought and control treatment were statistically not significantly different. Overall, daytime fluxes were large (12.5 ± 13.8 pmol m−2 s−1) in their magnitude and consistently positive compared to the previous studies, which predominantly used dark chambers. Nighttime measurements revealed soil COS fluxes around zero, as did measurements with darkened soil chambers during daytime reinforcing the importance of incoming solar radiation. Our results suggest that abiotic drivers play a key role in controlling in situ soil COS fluxes of the investigated grassland.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-016-3805-0) contains supplementary material, which is available to authorized users.

Assessing canopy performance using carbonyl sulfide measurements

“…In our region, MgSO 4 is a known salt component in soils (Singer, 2007), and its reaction with CO (present in relatively high concentrations in our urban atmosphere) under high soil temperatures could also produce COS (Ferm, 1957). It should also be noted that the measurements were conducted in darkened chambers, and these emissions are highly temperature-sensitive, in addition to light (Kitz et al, 2017;Liu et al, 2010;Whelan & Rhew, 2015;Whelan et al, 2016).…”

Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements

“…The COS soil flux was calculated using the following equation: where F is the COS soil flux (pmol m −2 s −1 ), q denotes the flowrate in (mol/s), C 2 and C 1 are the chamber and ambient mole fractions of COS in ppt, respectively, and A is the soil surface area (0.032 m 2 ) covered by the chamber. For a more detailed description see Kitz et al ().…”

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

“…However, recent discoveries challenge this assumption. Strong net emissions of COS have been observed from cropland soils at high temperature Whelan et al, 2016) and in an alpine grassland under solar radiation (Kitz et al, 2017), highlighting the crucial role of abiotic COS production in soil COS flux. In semiarid ecosystems, the rewetting of leaf litter after rainfall can stimulate pulses in COS uptake that temporarily overwhelm leaf COS uptake .…”