Response to the review comments on “Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland”

Soil is a major contributor to the biosphere–atmosphere exchange of carbonyl sulfide (COS) and carbon monoxide (CO). COS is [..1 ]a tracer to quantify terrestrial photosynthesis based on the [..2 ]coupled leaf uptake of COS and [..3 ]CO2, but [..4 ]such use requires separating soil COS flux[..5 ], which is unrelated to photosynthesis, from ecosystem COS uptake. For CO, soil is a [..6 ]significant natural sink that influences the tropospheric CO budget. [..7 ]In the boreal forest, magnitudes and variabilities of soil COS and CO fluxes remain poorly understood. We measured hourly 5 soil fluxes of COS, CO, and CO2 [..8 ]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[..9 ], with average uptake rates around 3 pmol m−2 s−1 for COS [..10 ]and 1 nmol m−2 s−1 for CO, respectively. Soil respiration showed seasonal dynamics controlled by soil temperature, peaking [..11 ]at around 4 μmol m−2 s−1 [..12 ]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 10 soil moisture changes through diffusion limitation. COS and CO fluxes did not appear to respond to temperature, although they both correlated well with soil respiration in specific temperature bins. [..13 ]However, COS : CO2 and 1removed: used to improve constraints on 2removed: link between 3removed: of 4removed: this use requires the 5removed: to be well quantified 6removed: main sink in natural environments 7removed: We measured 8removed: hourly 9removed: . Average uptake rates were 10removed: , 11removed: in late August and September with fluxes 12removed: and 13removed: We found that COS:CO2 and CO:CO2 flux ratios were modulated by temperature, possibly indicating