Does uncus effusus enhance methane emissions from grazed pastures on peat?

[摘要] Methane (CH₄) emissions from drained organic soils are generally low,but internal gas transport in aerenchymatous plants may result in localemission hotspots. In a paired-sample field study at three different siteswe measured fluxes of CH₄ with static chambers from adjacent samplingquadrats with and without Juncus effusus during four field campaigns. At all three sites,CH₄ was observed in the soil at all sampling depths (5 to 100 cm),and in most cases both above and below the groundwater table. During spring,local maxima suggested methanogenesis also took place above the water table atall three sites. We found significant CH₄ emissions at all three sites,but emission controls were clearly different. Across the three sites,average emission rates (±1 SE) for sampling quadrats with and withoutJ. effusus were 1.47 ± 0.28 and 1.37 ± 0.33 mg CH₄ m⁻² h⁻¹, respectively, with no overall effect of J. effusus onCH₄ emissions. However, a significant effect of J. effusus was seen at one ofthe three sites. At this site, local CH₄ maxima were closer to thesoil surface than at the other sites, and the upper soil layers were dryer.This could have affected both root CH₄ accessibility and CH₄ oxidation respectively, and together with limited gas diffusivity in thesoil column, cause elevated CH₄ emissions from J. effusus. We conclude thatJ. effusus has the potential to act as point sources of CH₄from drained peatlands, but more studies on the specific conditions underwhich there is an effect, are needed before the results can be used inmodelling of CH₄ emissions.

[学科分类] 地球化学与岩石