Relationships between greenhouse gas production and landscape position during short-term permafrost thaw under anaerobic conditions in the Lena Delta

Soils in the permafrost region have acted as carbon sinks for thousands of years. As a result of global warming, permafrost soils are thawing and will potentially release greenhouse gases (GHGs) such as methane (CHinline-formula₄) and carbon dioxide (COinline-formula₂). However, small-scale spatial heterogeneities of GHG production have been neglected in previous incubation studies. Here, we used an anaerobic incubation experiment to simulate permafrost thaw along a transect from upland Yedoma to the floodplain on Kurungnakh Island. Potential COinline-formula₂ and CHinline-formula₄ production was measured during incubation of the active layer and permafrost soils at 4 and 20 inline-formula^∘C, first for 60 d (approximate length of the growing season) and then continuing for 1 year. An assessment of methanogen abundance was performed in parallel for the first 60 d. Yedoma samples from upland and slope cores remained in a lag phase during the growing season simulation, while those located in the floodplain showed high production of CHinline-formula₄ (inline-formula6.5×10³ inline-formulaµg CHinline-formula₄-C ginline-formula⁻¹ C) and COinline-formula₂ (inline-formula6.9×10³ inline-formulaµg COinline-formula₂-C ginline-formula⁻¹ C) at 20 inline-formula^∘C. The Yedoma samples from the permafrost layer started producing CHinline-formula₄ after 6 months of incubation. We conclude that landscape position is a key factor triggering CHinline-formula₄ production during the growing season time on Kurungnakh Island.