Greenhouse Gas Emissions from Southward Transplanted Wetlands During Freezing-Thawing Periods in Northeast China

Abstract

Freezing-thawing in mid-high latitudes is an important factor controlling nutrient dynamics. We transplanted peatland columns (TQ) and freshwater marsh columns (SJ) in different latitudes into south seasonal frozen regions to determine the responses of greenhouse gas emissions from different wetlands to the freezing-thawing under climate warming. The decrease in CO₂ and CH₄ emissions during freezing stage were interrupted by a short emission peak. While N₂O uptake rate reduced with decreasing temperature. In the thawing stage, all the three greenhouse gases exhibited emission peaks. CO₂ were 159.83 mg m⁻² h⁻¹ (TQ) and 86.83 mg m⁻² h⁻¹ (SJ); CH₄ were 1.32 mg m⁻² h⁻¹ (TQ) and 4.07 mg m⁻² h⁻¹ (SJ); N₂O were 72.14 ug m⁻² h⁻¹ (TQ) and 22.15 ug m⁻² h⁻¹ (SJ). Meanwhile, N₂O transferred from sink into source. With temperature increase, the emission rate of CO₂ increased fast, while CH₄ and N₂O decreased. CO₂ emission during freezing-thawing periods was significantly correlated with soil temperature and CH₄ emission. Soil active organic carbon also played important roles in greenhouse gases emissions. Our study suggested that more greenhouse gases may release from wetlands into atmosphere in the context of global warming, and the potential release of CO₂ and N₂O during freezing-thawing periods was much higher in peatlands of permafrost zone.