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\hypersetup{pdftitle={Effect of Climate Change on Fitting two Forage Crop Seedling Emergences with Nonlinear Regression Models},pdfauthor={Behnam Behtari, Adel Dabbagh Mohammadi Nasab},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Modelling, seedling emergence, tall fescue, wheatgrass },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{Effect of Climate Change on Fitting two Forage Crop Seedling Emergences with Nonlinear Regression Models\footnote{\textbf{Contact Address:} Behnam Behtari, Islamic Azad University, Tabriz Branch, Dept. of Crop Ecology, Daneshgah, Tabriz, Iran, \mbox{e-mail}: \email{behtari@live.com}}\\[0.8ex]}}
\normalsize{\textsc{Behnam Behtari$^{1}$, Adel Dabbagh Mohammadi Nasab$^{2}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$Islamic Azad University, Tabriz Branch, Dept. of Crop Ecology, Iran}}}
\item[]{\small{\textit{$^{2}$Tabriz University, Dept. of Agronomy and Plant Breeding, Iran}}}
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\index[author]{Behtari, Behnam}
\index[author]{Dabbagh Mohammadi Nasab, Adel}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Model the behaviour of a system before committing to large"=scale investment. Nonlinear regression models have been developed to explain plant emergence patterns as a function of thermal time. Seeding emergence models could aid in the design of practices for managing native or introduced plant populations. Several mathematical models have been developed that predict seeding emergence, with some success, one of the most significant limitations to the advancement of such models is the existence of temperature. Quantitative information about temperature effects on seedling emergence in tall fescue (\textit{Festuca arundinacea }Schreb) and wheatgrass (\textit{Agropyron desertorum} (Fisch. ex Link) J.A. Schultes) is scarce. The main objective of this study was to develop a seedling emergence thermal time model for tall fescue and wheatgrass. To do this, we used the seedling emergence data of two forage crop species in two sites with different climate (semiarid and humid) and equations fit to the data used Gompertz, logistic, Verhulst, Weibull and Richards model. The results indicated that climate had similar effects on nonlinear regression models. Between the humid site and semiarid site models, the predicted change in emergence of Fescue and Wheatgrass affected by degree"=days were not different with observed value. Differences in the seedling emergence of plant species were least at semiarid site, while the differences between species in the humid site were high. Curving fitting generally gave efficiency $\geq$ 0.99 in all case. Among the five models, the Gompertz and weibull models gave quit satisfactory results, as the predicted values from the experiment were close (RMSD $\leq$ 1.1).}

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\noindent \textbf{Keywords:} Modelling, seedling emergence, tall fescue, wheatgrass 
\index[key]{Modeling}
\index[key]{Seedling emergence}
\index[key]{Tall fescue}
\index[key]{Wheatgrass }
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