Seasonal and Spatial Variability of Biological N2 Fixation in a Cool Temperate Bog

作者：Tatjana Živković, Manuel Helbig, Tim R. Moore · 发表于：Journal of Geophysical Research Biogeosciences · 年份：2022 · DOI：10.1029/2021jg006481 · 被引用次数：11 · 研究领域：Peatlands and Wetlands Ecology、Botany and Plant Ecology Studies、Coastal wetland ecosystem dynamics

Abstract Northern peatlands are globally important carbon (C) and nitrogen (N) sinks due to slow decomposition rates resulting in long‐term organic matter accumulation. Despite their large N storage, peatlands depend on sources of bio‐available N to sustain their biomass production. Di‐nitrogen (N 2 ) fixation represents an important biological N source in ombrotrophic bogs, but its environmental controls are still poorly understood. We examined seasonal and spatial variability of Sphagnum ‐associated N 2 fixation across a hydrological transect (hummock‐hollow‐beaver pond edge) in a temperate ombrotrophic bog. We measured N 2 fixation in live Sphagnum plants by acetylene reduction assay calibrated with a 15 N 2 tracer method, bi‐weekly, from May to November over two growing seasons. We found that N 2 fixation increased with soil temperature at 5 cm in the living Sphagnum mat explaining the seasonal variability in N 2 fixation. Peak N 2 fixation rates occur in mid‐August, when N 2 fixation rates are about 10 times larger than during the shoulder seasons (May and November). Spatially, N 2 fixation was larger in wetter Sphagnum with larger gravimetric water content in Sphagnum . This relationship was most pronounced in the peak growing season when N 2 fixation rates were the highest. Finally, we estimated that the Mer Bleue bog receives around 0.3 g N m −2 annually through Sphagnum ‐associated N 2 fixation, which accounts for about a fourth of the N accumulated annually into Sph...