Regulation of methane production, oxidation, and emission by vascular plants and bryophytes in ponds of the northeast Siberian polygonal tundra

Abstract

Abstract Methane (CH 4 ) production, oxidation, and emission were studied in ponds of the permafrost‐affected polygonal tundra in northeast Siberia. Microbial degradation of organic matter in water‐saturated soils is the most important source for the climate‐relevant trace gas CH 4 . Although ponds and lakes cover a substantial fraction of the land surface of northern Siberia, data on CH 4 fluxes from these water bodies are scarce. Summer CH 4 fluxes were measured with closed chambers at the margins of ponds vegetated by vascular plants and in their centers without vascular plants. Furthermore, CH 4 and oxygen concentration gradients, stable carbon isotope signatures of dissolved and emitted CH 4 , and microbial CH 4 production and CH 4 oxidation were determined. Mean summer fluxes were significantly higher at the margins of the ponds (46.1 ± 15.4 mg CH 4 m −2 d −1 ) than at the centers (5.9 ± 8.2 mg CH 4 m −2 d −1 ). CH 4 transport was dominated by diffusion in most open water sites, but substantial ebullitive fluxes (12.0 ± 8.1 mg CH 4 m −2 d −1 ) were detected in one pond. Plant‐mediated transport accounted for 70 to 90% of total CH 4 fluxes above emerged vegetation. In the absence of vascular plants, 61 to 99% of the CH 4 produced in the anoxic bottom soil was consumed in a layer of the submerged moss Scorpidium scorpioides , which covered the bottoms of the ponds. The fraction of CH 4 oxidized was lower at sites with vascular plants since CH 4 was predominantly transported through their aerenchyma, thereby bypassing the CH 4 oxidation zone in the moss layer. These results emphasize the importance of moss‐associated CH 4 oxidation causing low CH 4 fluxes from the studied Siberian ponds.