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\hypersetup{pdftitle={Small Amounts of Salt Stimulates Regrowth of \textit{Leymus chinensis} and \textit{Stipa baicalensis }after Clipping in Semi"=arid Grassland},pdfauthor={Yingzhi Gao, Yanhua Wang, Fang Yang, Z.J. Li, Folkard Asch, Marcus Giese},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Grazing, steppe, productivity , salt-stress},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\begin{center}
\Large{\textbf{Small Amounts of Salt Stimulates Regrowth of \textit{Leymus chinensis} and \textit{Stipa baicalensis }after Clipping in Semi"=arid Grassland\footnote{\textbf{Contact Address:} Yingzhi Gao, Northeast Normal University, Institute of Grassland Science, Renmin Street 5268, 100024~Changchun, China, \mbox{e-mail}: \email{Yingzhigao220@163.com}}\\[0.8ex]}}
\normalsize{\textsc{Yingzhi Gao$^{1,2}$, Yanhua Wang$^{1,2}$, Fang Yang$^{1}$, Z.J. Li$^{1}$, Folkard Asch$^{2}$, Marcus Giese$^{2}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$Northeast Normal University, Key Laboratory of Vegetation Ecology, China}}}
\item[]{\small{\textit{$^{2}$University of Hohenheim, Dept. of Plant Production and Agroecology in the Tropics and Subtropics, Germany}}}
\end{itemize*}
\index[author]{Gao, Yingzhi}
\index[author]{Wang, Yanhua}
\index[author]{Yang, Fang}
\index[author]{Li, Z.J.}
\index[author]{Asch, Folkard}
\index[author]{Giese, Marcus}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Overgrazing in the Northern Chinese steppe ecosystems often enhanced degradation processes and for the Songen grasslands salinisation turned out to be an additional major thread for livestock farming. \textit{Leymus chinensis} and \textit{Stipa baicalensis} are the dominant grass species and important fodder plants but their response to salt stress is largely unknown. We treated two grassland sites each dominated by one of these two species with mixed salt"=alkali solution and three clippings within one growing season to test how salt stress and defoliation affected above and belowground biomass productivity and regrowth performance. 



Clipping alone had no effects on belowground productivity (stem base, rhizome, and roots), while it significantly decreased shoot biomass and increased the root/shoot ratio (R/S) of \textit{L. chinensis}, whereas no significant effect on \textit{S. baicalensis }was observed. Salt alone had no significant effect on productivity of both species. The combined effects of salt and clipping decreased the R/S of L. chinensis, but not that of \textit{S. baicalensis}. Salt treatment increased regrowth biomass of both species after clipping. The regrowth of \textit{S. baicalensis} was significantly higher than that of \textit{L. chinensis}. 



Our results indicate that small amounts of salt can stimulate regrowth ability of both species. This salt stimulation was unexpected since no studies reported positive effects of salt on plant regrowth so far. Reasons are speculative, but one option could be the increased nutrient release promoted by salt application from the soil matrix. Another hypothesis is that moderate availability of Na$^{+}$ increases osmotic potential of plant cells, and promotes leaf cell division and plant photosynthetic ability. However, many grasslands of Northern China are degraded by extremely high salt/alkaline conditions resulting from overgrazing and related effects. Our findings suggest the existence of a threshold value of positive salt effects on plant regrowth under grazing which might support moderate grazing intensities rather on (medium) salt affected than on non salt affected grasslands. Further research is certainly needed to obtain more evidence about salt effects on semi"=arid grasslands ecosystems under grazing, especially with regard to variable water availability. 



}

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\noindent \textbf{Keywords:}  steppe, grazing, productivity , salt"=stress
\index[key]{Steppe}
\index[key]{Grazing}
\index[key]{Productivity }
\index[key]{Salt"=stress}
\end{document}