Direct contribution of nitrogen deposition to nitrous oxide emissions in a temperate beech and spruce forest – a <sup>15</sup>N tracer study

Abstract

Abstract. The impact of atmospheric nitrogen (N) deposition on nitrous oxide (N2O) emissions in forest ecosystems is still unclear. The objective of our study was to investigate the direct contribution of N deposition to N2O emissions in temperate forests exposed to chronic high N deposition using a 15N labelling technique. In a Norway spruce stand (Picea abies) and in a beech stand (Fagus sylvatica) in the Solling, Germany, we added a low concentrated 15N-labelled ammoniumnitrate solution to simulate N deposition. Nitrous oxide fluxes and 15N isotope abundances in N2O were measured using the closed chamber method combined with 15N isotope analyses. Emissions of N2O were higher in the beech stand (2.6 ± 0.6 kg N ha−1 yr−1) than in the spruce stand (0.3 ± 0.1 kg N ha−1 yr−1). We observed a direct effect of N input on 15N2O emissions, which lasted less than three weeks and was mainly caused by denitrification. No progressive increase in 15N enrichment of N2O occurred over a one-year experiment, which we explained by immobilisation of deposited N. The annual emission factor for N2O from deposited N was 0.1% for the spruce stand and 0.6% for the beech stand. Standard methods used in the literature applied to the same stands grossly overestimated emission factors with values of up to 25%. Only 6–13% of the total N2O emissions were derived from direct N deposition. Whether the remaining emissions resulted from accumulated anthropogenic N deposition or native N, can not be distinguish with the applied methods. The 15N tracer technique represents a precise tool, which may improve estimates of the current contribution of N deposition on N2O emissions.

A regional assessment of land‐based carbon mitigation potentials: Bioenergy, BECCS, reforestation, and forest management

“…However, potential nitrous oxide (N 2 O) emissions from increased nitrogen input could substantially reduce the net effect of nitrogen fertilization. While N 2 O emissions from fertilizer application might be higher in deciduous forests than in coniferous forests (Eickenscheidt, Brumme, & Veldkamp, ), assuming the default IPPC emission factor of 1% and a 296 times greater warming potential than CO 2 (Hastings et al, ), potential cumulative N 2 O emissions correspond to a carbon equivalent of 16 ± 0.5 Mt C. The carbon mitigation potential of nitrogen addition to forests could thereby be reduced by around 26%.…”

The potential for N2O emission and nitrate leaching in seasonally open solar greenhouses during the summer fallow: a 15N tracer study

“…The 15 N‐N 2 O abundance of N 2 O emitted from the soil was calculated using the Keeling plot approach (Yakir & Sternberg, ; Eickenscheidt et al ., ):where c(N 2 O) is the concentration of N 2 O and 15 N is the abundance of 15 N in N 2 O calculated as described in Equation . The 15 N emitted excess value was calculated by subtracting the 15 N emitted value of the control chambers.…”

Impacts of nitrogen deposition on soil nitrogen cycle in forest ecosystems: A review

“…In general, N losses through denitrification are low in natural forest ecosystems [1,2]. The rates of denitrification are far below 1 kg N hm −2 year −1 in the N-limited forests [15,39]. The emissions of N2O are less than 2 kg N hm −2 year −1 even in the N-rich tropical forests [6,10,17].…”