Dynamic measurements of CH₄, H₂, and CO uptake by soil using a flow-through chamber system-temporal and incubation temperature dependence of gas uptake

Soil gas exchange plays a crucial role in biogeochemical cycles and is influenced by various environmental factors, particularly temperature. This study investigated the effects of temperature variation on the uptake of hydrogen (H2), carbon monoxide (CO), and methane (CH4) by volcanic ash soils from forests and arable land using a dynamic flow-through chamber system. The objective of this study was to elucidate how both short-period and long-period temperature changes influence gas uptake by these soils ("3 h temperature treatments" vs. "temperature treatments over 2 weeks to 2 months during the pre-incubation"). The study found that the uptake rates of H2 and CO were higher in forest soil than in arable soil. Across all long-period temperature treatments, H2 and CO uptake rates were highest at short-period temperatures of 25－35℃ within the tested range (－5－45℃). CH4 uptake was lower than H2 and CO uptake, with forest soil taking up more CH4 than arable soil. The optimal temperature for CH4 uptake under 5－35℃ of short-period temperature with 25℃ of long-period temperature was 30℃ for both soil types. Heat stress had an irreversible effect on CH4 uptake, with a more pronounced decrease in the forest soil. The differing effects of short-period and long-period temperature treatments on soil uptake of these gases highlight the need to incorporate temperature variations across different timescales into soil gas exchange models. The findings also provide insights into soil gas exchange processes under temporary temperature increases caused by extreme weather events and diurnal changes.