English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. Common methods for measuring soil denitrification in situinclude monitoring the accumulation of 15N -labelled N2 and N2O evolved from 15N -labelled soil nitrate pool in closed chambersthat are placed on the soil surface. Gas diffusion is considered to be themain transport process in the soil. Because accumulation of gases within thechamber decreases concentration gradients between soil and the chamber overtime, the surface efflux of gases decreases as well, and gas production ratesare underestimated if calculated from chamber concentrations withoutconsideration of this mechanism. Moreover, concentration gradients to thenon-labelled subsoil exist, inevitably causing downward diffusion of 15N -labelled denitrification products. A numerical 3-D model forsimulating gas diffusion in soil was used in order to determine thesignificance of this source of error. Results show that subsoil diffusion of 15N -labelled N2 and N2O – and thus potential underestimationof denitrification derived from chamber fluxes – increases with chamberdeployment time as well as with increasing soil gas diffusivity. Simulationsbased on the range of typical soil gas diffusivities of unsaturated soilsshowed that the fraction of N2 and N2O evolved from 15N -labelled NO 3 - that is not emitted at the soil surfaceduring 1 h chamber closing is always significant, with values up to >50  % of total production. This is due to accumulation in thepore space of the 15N -labelled soil and diffusive flux to theunlabelled subsoil. Empirical coefficients to calculate denitrification fromsurface fluxes were derived by modelling multiple scenarios with varyingsoil water content. Modelling several theoretical experimental set-upsshowed that the fraction of produced gases that are retained in soil can belowered by lowering the depth of 15N labelling and/or increasing thelength of the confining cylinder. Field experiments with arable silt loam soil for measuring denitrificationwith the 15N gas flux method were conducted to obtain direct evidencefor the incomplete surface emission of gaseous denitrification products. Wecompared surface fluxes of 15N2 and 15N2O from 15N -labelled micro-plots confined by cylinders using the closed-chamber method with cylinders open or closed at the bottom, finding 37 %higher surface fluxes with the bottom closed. Modelling fluxes of this experimentconfirmed this effect, however with a higher increase in surface flux of89 %. From our model and experimental results we conclude that field surfacefluxes of 15N -labelled N2 and N2O severely underestimatedenitrification rates if calculated from chamber accumulation only. Theextent of this underestimation increases with closure time. Underestimationalso occurs during laboratory incubations in closed systems due to porespace accumulation of 15N -labelled N2 and N2O . Due to thisbias in past denitrification measurements, denitrification in soils might bemore relevant than assumed to date. Corrected denitrification rates can be obtained by estimating subsurfaceflux and storage with our model. The observed deviation between experimentaland modelled subsurface flux revealed the need for refined model evaluation,which must include assessment of the spatial variability in diffusivity andproduction and the spatial dimension of the chamber.

biogeosciences

Underestimation of denitrification rates from field application of the &amp;lt;sup&amp;gt;15&amp;lt;/sup&amp;gt;N gas flux method and its correction by gas diffusion modelling