Nitrogen translocation in Sphagnum mosses: effects of atmospheric nitrogen deposition

Abstract

Summary• Here, the hypothesis was tested that nitrogen (N) translocation from older to younger parts of Sphagnum decreases as N inputs from atmospheric deposition increase.• Nitrogen translocation in Sphagnum mosses was compared in bogs with contrasting atmospheric N deposition (Adirondack -relatively high N deposition; Mainerelatively low) and by following the movement of a 15 NH 4 15 NO 3 tracer applied to plots of Sphagnum capillifolium over 2 yr.• Annual N translocation ranged from 11% to > 80% in the lower and higher influx sites, respectively. Nitrogen translocation was an important process for the N budget of the Sphagnum mosses, contributing 0.5-11% of the annual N requirements. These results suggest that N translocation is as important as direct N retention from atmospheric deposition for the N budget of the mosses. Contrary to expectations, N translocation was greater in the high (Adirondack) than in the low (Maine) deposition sites.• If N translocation is closely tied to water availability, the relative positions of the water tables in the sites over the course of the experiments might account for differences in N translocation among sites. The lower translocation (Maine) sites had lower water tables in the first year of the experiment and experienced a more severe drought in the second year than did the Adirondack sites.

Methanotrophy induces nitrogen fixation during peatland development

“…Despite the low absolute areal rate of N 2 fixation in the older mainly rainwater-fed stages (fen-bog transitions), where moss growth is more nutrient limited, the comparison of Sphagnum growth rates (26) and N contents further suggests that the proportion of fixed N of the new biomass N increment may increase to 58%. The rest of the N is, we presume, being taken up as inorganic ions and organic N, or recycled to new growth from older parts of the moss shoot (29). The time scale at which N fixed in the moss becomes available for the moss host and for other plants may range from fast exchange over a time span of days (6,11) to slower nutrient release from decomposing Sphagnum litter over a period of years.…”

Geotropic curvatures of Sphagnum: environmental features of their genesis and trial application for estimation shoot length increment

“…The growth of Sphagnum mosses is badly affected not only by tied threads but also by the cutting-off the plants to known initial length -a method used to estimate the increment of pool moss species. As a result, natural translocation within a shoot is disturbed (Rydin & Clymo, 1989;Aldous, 2002), the surfaces and cavities colonized by diazotrophic and methanotrophic microorganisms are considerably reduced (Raghoebarsing et al, 2005;Ho & Bodelier, 2015) and the natural assimilation and transport of biogenic chemical elements are disturbed. It seems to be the reason why the increments estimated by this method are so low even for rapidly growing species (Sonesson et al, 1980;Hulme & Blyth, 1982).…”

N2-fixation by methanotrophs sustains carbon and nitrogen accumulation in pristine peatlands

“…These high rates of N-accumulation and large moss N-demand can be explained neither by atmospheric deposition, nor by mechanisms of internal recycling. A 15 N tracer study showed that only 1.3-11.4 % of the annual N demand of growing Sphagnum is provided by upward retranslocation (Aldous 2002), which in Alberta bogs, would be equivalent to a maximum of 4.5 kg ha -1 year -1 . Similarly, N mineralization can provide recycled N to support new growth, but our measured rates in Alberta bogs are low, providing only 1.2 kg ha -1 year -1 (Online Resource 2).…”