Soil COS Exchange: A Comparison of Three European Ecosystems

Florian Kitz,Albin Hammerle,Olaf Kolle,Dmitrii Krasnov,Georg Wohlfahrt,Gerardo Moreno,Steffen M. Noe,Andreas Ibrom,Felix M. Spielmann,Mirco Migliavacca

doi:10.1029/2019gb006202

Abstract

AbstractThe potential of carbonyl sulfide (COS) flux measurements as an additional constraint for estimating the gross primary production depends, among other preconditions, on our understanding of the soil COS exchange and its contribution to the overall net ecosystem COS flux. We conducted soil chamber measurements of COS, with transparent chambers, in three different ecosystems across Europe. The in situ measurements were followed by laboratory measurements of soil samples collected at the study sites. The soil samples were exposed to UV radiation to investigate the role of photo‐degradation for COS exchange. In situ and laboratory measurements revealed pronounced intersite and intrasite variability of COS exchange. In situ COS fluxes were primarily governed by radiation in the savannah‐like grassland (SAV), soil temperature and intrasite heterogeneity in the deciduous broadleaf forest, and soil water content and intrasite heterogeneity in the evergreen needleleaf forest. The soil of the ecosystem with the highest light intensity incident on the soil surface, SAV, was a net source for COS, while the soils of the other two ecosystems were COS sinks. UV radiation increased COS emissions and/or reduced COS uptake from all soil samples under laboratory conditions. The impact of UV on the COS flux differed between soil samples, with a tendency toward a stronger response of the COS flux to UV radiation exposure in samples with higher soil organic matter content. Our results emphasize the importance of photo‐degradation for the soil COS flux and stress the substantial spatial variability of soil COS exchange in ecosystems.

Highlights

Measurements of the trace gas carbonyl sulfide (COS) have been discussed as a promising tool for inferring gross primary production (GPP) and stomatal conductance at the ecosystem scale (Sandoval‐Soto et al, 2005; Seibt et al, 2010; Wehr et al, 2017; Whelan et al, 2018; Wohlfahrt et al, 2012)
Mean COS fluxes during daytime were highest in the savannah‐like grassland (SAV) and lowest in the evergreen needleleaf forest (ENF), while nighttime COS fluxes were lowest in the deciduous broadleaf forest (DBF) (Table 1)
Nighttime in situ COS fluxes from the SAV were significantly different from the DBF (p value

Summary

Introduction

Measurements of the trace gas carbonyl sulfide (COS) have been discussed as a promising tool for inferring gross primary production (GPP) and stomatal conductance at the ecosystem scale (Sandoval‐Soto et al, 2005; Seibt et al, 2010; Wehr et al, 2017; Whelan et al, 2018; Wohlfahrt et al, 2012). COS sparked the interest of researchers because its uptake by plants is closely linked to the uptake of CO2 (Seibt et al, 2010). Both gases enter the leaf via similar pathways and are subsequently consumed by the same enzymes, especially the enzyme carbonic anhydrase (CA) (Seibt et al, 2010; Stimler et al, 2010). No COS emissions from vascular plants have been reported. This would in theory and in the absence of other ecosystem sources and sinks equate the measured COS flux at the ecosystem level to the COS uptake by plants, which could be used to infer the CO2 plant uptake. COS and CO2 measurements together, both on the ecosystem level, could improve the partitioning of the net ecosystem CO2 flux into GPP and respiration

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Conclusion