CO₂ and CH₄ fluxes from forest soil in the northern Da Xing'anling Mountains in Northeast China during the freezing and thawing periods of near-surface soil in 2018-2019

Under a warming climate, the studies on effects of seasonal freeze-thaw cycles on soil respiration are key to understanding the soil carbon cycles and ecosystem responses and resilience at mid- and high latitudes. In this study, the effluxes of soil surface CO2 and absorption rates of CH4 were measured in the Xing'an larch (Larix gmelinii) forest in the northern Da Xing'anling Mountains, Northeast China using an automatic multichannel soil greenhouse gas measurement system (dynamic gas chamber method) during the periods of October-November 2018 and April-May 2019. The results showed that during the freezing period of near-surface soil, CO2 and CH4 fluxes significantly declined, approaching zero, at the end of November. During the thawing period of near-surface soil, CO2 and CH4 fluxes from surface soil fluctuated markedly at first and then rose rapidly. The respective Q(10) values of 3.86 and 4.89 during the freezing and thawing periods of near-surface soil, respectively, indicate the important role of ground freeze-thaw cycles in the modifications of CO2 and CH4 fluxes. The results of this study could help assess the stability of the soil carbon pool and carbon flux strength in taiga-forested permafrost regions in the northern Da Xing'anling Mountains, Northeast China.