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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-11-9333-2011</article-id>
<title-group>
<article-title>Trace gas fluxes of CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O in a permanent grassland soil exposed to elevated CO&lt;sub&gt;2&lt;/sub&gt; in the Giessen FACE study</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kaleem Abbasi</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Müller</surname>
<given-names>C.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Soil and Environmental Sciences University of Azad Jammu and Kashmir, Faculty of Agriculture, Rawalakot, Azad Jammu and Kashmir, Pakistan</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Department of Plant Ecology, Justus-Liebig University Giessen, Heinrich-Buff-Ring 26, 35392 Giessen, Germany</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>School of Biology and Environmental Science, University College Dublin, Belfield, Dublin, Ireland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>09</day>
<month>09</month>
<year>2011</year>
</pub-date>
<volume>11</volume>
<issue>17</issue>
<fpage>9333</fpage>
<lpage>9342</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-chem-phys.net/11/9333/2011/acp-11-9333-2011.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/9333/2011/acp-11-9333-2011.pdf</self-uri>
<abstract>
<p>Long-term field observations showed that N&lt;sub&gt;2&lt;/sub&gt;O fluxes observed shortly
after N application were not significantly affected by elevated CO&lt;sub&gt;2&lt;/sub&gt; in
the Giessen Free Air Carbon dioxide Enrichment (FACE) study. To further
investigate this unexpected result a &lt;sup&gt;15&lt;/sup&gt;N tracer study was carried out
under controlled conditions where in parallel treatments either the
NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; pool (&lt;sup&gt;15&lt;/sup&gt;NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt;) or the NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; pool
(NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;15&lt;/sup&gt;NO&lt;sub&gt;3&lt;/sub&gt;) was enriched with &lt;sup&gt;15&lt;/sup&gt;N. Fluxes of CO&lt;sub&gt;2&lt;/sub&gt;,
CH&lt;sub&gt;4&lt;/sub&gt;, and N&lt;sub&gt;2&lt;/sub&gt;O as well as the &lt;sup&gt;15&lt;/sup&gt;N enrichment of the N&lt;sub&gt;2&lt;/sub&gt;O
were measured. Denitrifying Enzyme Activity (DEA), total denitrification
(N&lt;sub&gt;2&lt;/sub&gt; + N&lt;sub&gt;2&lt;/sub&gt;O) and N&lt;sub&gt;2&lt;/sub&gt;-to-N&lt;sub&gt;2&lt;/sub&gt;O ratios were quantified in
separate experiments. Over the 57 day incubation, N&lt;sub&gt;2&lt;/sub&gt;O fluxes averaged
0.090 ng N&lt;sub&gt;2&lt;/sub&gt;O-N g&lt;sup&gt;−1&lt;/sup&gt; h&lt;sup&gt;−1&lt;/sup&gt; under ambient and 0.083 ng N&lt;sub&gt;2&lt;/sub&gt;O-N g&lt;sup&gt;−1&lt;/sup&gt; h&lt;sup&gt;−1&lt;/sup&gt; under elevated CO&lt;sub&gt;2&lt;/sub&gt; (not significantly
different). The N&lt;sub&gt;2&lt;/sub&gt;O production processes were identified by a
two-source model. Results showed that N&lt;sub&gt;2&lt;/sub&gt;O must have also been produced
by a third source – possibly related to organic N transformation – which
was stimulated by elevated CO&lt;sub&gt;2&lt;/sub&gt;. Soil CO&lt;sub&gt;2&lt;/sub&gt; fluxes were approximately
20 % higher under elevated CO&lt;sub&gt;2&lt;/sub&gt; than soil from ambient but the
differences were not significant. CH&lt;sub&gt;4&lt;/sub&gt; oxidation rates were on average
−1.75 ng CH&lt;sub&gt;4&lt;/sub&gt;-C g&lt;sup&gt;−1&lt;/sup&gt; h&lt;sup&gt;−1&lt;/sup&gt; in the elevated and
−1.17 ng CH&lt;sub&gt;4&lt;/sub&gt;-C g&lt;sup&gt;−1&lt;/sup&gt; h&lt;sup&gt;−1&lt;/sup&gt; in the ambient indicating that elevated
CO&lt;sub&gt;2&lt;/sub&gt; increased the CH&lt;sub&gt;4&lt;/sub&gt; oxidation by 49 % compared to ambient
CO&lt;sub&gt;2&lt;/sub&gt; under controlled conditions. N fertilization increased CH&lt;sub&gt;4&lt;/sub&gt;
oxidation by 3-fold in both CO&lt;sub&gt;2&lt;/sub&gt; treatments. CO&lt;sub&gt;2&lt;/sub&gt; did not have any
significant effect on DEA while total denitrification and
N&lt;sub&gt;2&lt;/sub&gt;-to-N&lt;sub&gt;2&lt;/sub&gt;O ratios increased by 36 and 33 %, respectively. The
results indicate that shortly after N application elevated CO&lt;sub&gt;2&lt;/sub&gt; must
have stimulated both the N&lt;sub&gt;2&lt;/sub&gt;O production and reduction to N&lt;sub&gt;2&lt;/sub&gt; to
explain the increased N&lt;sub&gt;2&lt;/sub&gt;-to-N&lt;sub&gt;2&lt;/sub&gt;O ratio and at the same time explain
the non-responsiveness of the N&lt;sub&gt;2&lt;/sub&gt;O emissions. Thus, the observed
variation of the CO&lt;sub&gt;2&lt;/sub&gt; effect on N&lt;sub&gt;2&lt;/sub&gt;O emissions throughout the year
is possibly governed by the dynamics of the N&lt;sub&gt;2&lt;/sub&gt;O reductase activity.</p>
</abstract>
<counts><page-count count="10"/></counts>
</article-meta>
</front>
<body/>
<back>
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