 |
| Titel |
Nitrous oxide emissions from managed grassland: a comparison of eddy covariance and static chamber measurements |
| VerfasserIn |
S. K. Jones, D. Famulari, C. F. Marco, E. Nemitz, U. M. Skiba, R. M. Rees, M. A. Sutton |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 4, no. 10 ; Nr. 4, no. 10 (2011-10-17), S.2179-2194 |
| Datensatznummer |
250002117
|
| Publikation (Nr.) |
 copernicus.org/amt-4-2179-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| Managed grasslands are known to be an important source of N2O with
estimated global losses of 2.5 Tg N2O-N yr−1. Chambers are to date
the most widely used method to measure N2O fluxes, but also
micrometeorological methods are successfully applied. In this paper we present
a comparison of N2O fluxes measured by non-steady state chambers and
eddy covariance (EC) (using an ultra-sonic anemometer coupled with a tunable
diode laser) from an intensively grazed and fertilised grassland site in
South East Scotland. The measurements were taken after fertilisation events
in 2003, 2007 and 2008. In four out of six comparison periods, a short-lived
increase of N2O emissions was observed after mineral N application,
returning to background level within 2–6 days. Highest fluxes were measured
by both methods in July 2007 with maximum values of 1438 ng N2O-N
m−2 s−1 (EC) and 651 ng N2O-N m−2 s−1 (chamber
method). Negative fluxes above the detection limit were observed in all
comparison periods by EC, while with chambers, the recorded negative fluxes
were always below detection limit. Median and average fluxes over each
period were always positive. Over all 6 comparison periods, 69% of
N2O fluxes measured by EC at the time of chamber closure were within
the range of the chamber measurements. N2O fluxes measured by EC during
the time of chamber closure were not consistently smaller, neither larger,
compared to those measured by chambers: this reflects the fact that the
different techniques integrate fluxes over different spatial and temporal
scales. Large fluxes measured by chambers may be representing local hotspots
providing a small contribution to the flux measured by the EC method which
integrates over a larger area. The spatial variability from chamber
measurements was high, as shown by a coefficient of variation of up to 139%. No diurnal pattern of N2O fluxes was observed, possibly due to
the small diurnal variations of soil temperature. The calculation of
cumulative fluxes using different integration methods showed EC data provide
generally lower estimates of N2O emissions than chambers. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|