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\hypersetup{pdftitle={N-oxides Fluxes, N$_{2}$O Sources, and Soil"=profile N$_{2}$O Concentrations of Tropical Forests after Chronic N Addition},pdfauthor={Juvia Sueta, Marife Corre},pdfsubject={Tropentag 2011: Abstract},pdfkeywords={Chronic N-addition, denitrification and nitrification, N-oxides, tropical forest},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, October 5-7, 2011, Bonn}}\\[1ex] \Large{``Development on the margin''\\[2ex]}}
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\begin{center}
\Large{\textbf{N-oxides Fluxes, N$_{2}$O Sources, and Soil"=profile N$_{2}$O Concentrations of Tropical Forests after Chronic N Addition\footnote{\textbf{Contact Address:} Juvia Sueta, Georg-August-Universität Göttingen, Soil Science of Tropical and Subtropical Ecosystems, Buesgenweg 2, 37077~Goettingen, Germany, \mbox{e-mail}: \email{jsueta@gwdg.de}}\\[0.8ex]}}
\normalsize{\textsc{Juvia Sueta, Marife Corre}}
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\begin{itemize*}
\item[]{\small{\textit{Georg-August-Universität Göttingen, Soil Science of Tropical and Subtropical Ecosystems, Germany}}}
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\index[author]{Sueta, Juvia}
\index[author]{Corre, Marife}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
N deposition is projected to increase in tropical region and emissions of climate"=relevant N-oxide (NO and N$_{2}$O) gases are expected to rise. However, few studies quantify long"=term impact of increased N availability on these gases and on the processes responsible for their production. We used N addition experiments to achieve N-enriched conditions in contrasting montane (3--4-yr N addition) and lowland (11--12-yr N addition) forests in Panama. Control and N-addition (receiving \mbox{125\,kg} urea-N ha$^{-1}$ yr$^{-1}$) treatments were represented by four (40 m\,$\times$\,\mbox{40\,m}) replicate plots each. We wanted to 1) quantify changes in surface N-oxide fluxes during N addition in tropical montane and lowland forests and 2) assess the contribution of denitrification and nitrification to the surface N$_{2}$O fluxes and deduce which process might be dominant at lower depths.



	



In the montane forest, N-oxide fluxes from N-addition plots were higher than the control. During the two"=year measurement period (2008--2009), a two"=fold increase in annual N$_{2}$O fluxes was observed while annual NO fluxes decreased from the N addition plots. Nitrification contributed $\geq$\mbox{60\,\%} to the N$_{2}$O flux from both treatment plots while $\leq$\mbox{40\,\%} was attributed to denitrification. In the lowland forest, N-oxide fluxes from N-addition plots were also higher than the control. Annual N$_{2}$O and NO fluxes from the N-addition plots remained comparable. Denitrification appeared to be the dominant process producing N$_{2}$O in N-addition plots during both dry and wet seasons. In the control plots, nitrification accounted for \mbox{70\,\%} of the total flux during the wet season. At both sites, soil"=profile N$_{2}$O concentrations in the N-addition plots were significantly higher than the control, starting at about 40-cm depth. High water"=filled pore space ($\geq$\mbox{80\,\%}) at these depths suggests that denitrification might be the dominant process contributing to the measured N$_{2}$O concentrations.



 



}

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\end{abstract}
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\noindent \textbf{Keywords:} Chronic N-addition, denitrification and nitrification, N-oxides, tropical forest
\index[key]{Chronic N-addition}
\index[key]{Denitrification and nitrification}
\index[key]{N-oxides}
\index[key]{Tropical forest}
\end{document}