Denitrification triggered by nitrogen addition in Sphagnum magellanicum peat

Abstract

International audienceOmbrotrophic (rain-fed) Sphagnum-mires do not significantly contribute to gaseous nitrogen (N) emissions to the atmosphere. However, increasing levels of N deposition reduce Sphagnum growth and moss cover. As a consequence, higher amounts of mineral N reach the underlying peat beneath the moss layer. The aim of our work was to determine the effects of supplementary N inputs to peat beneath Sphagnum magellanicum carpets. Peat cores were incubated in controlled laboratory conditions of temperature and humidity, and the impact of increasing N inputs was evaluated on denitrification rates, basal respiration and methane emissions. Rates of denitrification were quickly stimulated by addition of 1 g N m-2 but rates were not significantly elevated in the short-term (9 days) by further additions of up to 10 g N m-2. Over a longer term period (up to 45 days), denitrification rates followed an exponential (10 g N m-2 addition) or a gamma (1 g N m-2) function. Findings from this study support the hypothesis that mineral-N addition in atmospheric deposition will have a negative effect on peat biogeochemistry, by modifying its N sink capacity via denitrification leading to a potential increase in N2O emissions

Nitrous oxide emission potentials of Burkholderia species isolated from the leaves of a boreal peat moss Sphagnum fuscum*

“…Some reports of hyperactive N 2 O emission from degraded Sphagnum bogs due to climate change and human impact 7,9,12,14,19) support our speculation In C 2 H 2 inhibition assay, (−) indicated no statistically significant difference between the treatment and the control shown in Fig. 4(B).…”

“…In a previous study, adding ammonium-nitrate (NH þ 4 :NO À 3 , 1:1 mixture) solution in boreal S. magellanicum-dominated peat triggered de novo synthesis of denitrification-associated enzymes in denitrifiers, leading to active N 2 O emission. 19) Sphagnum-dominated boreal peat soils have shown relatively high eubacterial diversity, in which acid-tolerable Burkholderia bacteria are one of the predominant populations of the community. 20) N 2 O-emitting Burkholderia spp.…”

Nitrate turnover in a peat soil under drained and rewetted conditions: results from a [15N]nitrate–bromide double-tracer study

“…Other studies showed stimulation of denitrification due to N addition [5,6,45,46]. Thus, low N gas losses, especially in the form of N 2 O cannot be excluded for the drained peat site either.…”

Release of nitrous oxide and dinitrogen from a transition bog under drained and rewetted conditions due to denitrification: results from a [15N]nitrate–bromide double-tracer study

“…In natural peatlands, high WTs lead to limited oxygen (O 2 ) and consequently limited NO − 3 availability (due to a low nitrification rate), and therefore generally to a low denitrification activity. A few studies, however, reported an increase in denitrification rates when NO − 3 was applied to these peat soils [27][28][29]. Because N 2 O reductase is inhibited in the presence of O 2 ( [30]), rising WT during rewetting of peatlands could cause a shift of the N 2 O/N 2 ratio in favour of N 2 .…”