My problem is similar to this question, the caption alignment of tabular table and longtable is different. I would like to have the caption to be consistent with the tabular form, with some white padding from the top margin and align to the left of the toprule. I have tried to use [singlelinecheck=off] as suggested but it didn t change anything. Then I want to try redefining the \LT@caption as suggested as another way but I have no idea how to redefine it to make it as the tabular one.
I am guessing some of the problem may be related to my preset margin but it didn't align correctly even when I remove the a4paper setting. Any help or insight would be highly appreciated. Thank you in advance!
\documentclass{article}
\usepackage{array}
\usepackage{changepage}
\usepackage[a4paper, vmargin=0.05cm, hmargin=0.1cm, marginparwidth=0.1cm,total={210mm,297mm}]{geometry}
\usepackage{rotating}
\usepackage[singlelinecheck=off]{caption}
\usepackage{booktabs}
\usepackage{pdflscape}
\usepackage{multirow, makecell, xcolor}
\usepackage[separate-uncertainty=true]{siunitx}
\usepackage{threeparttable}
\usepackage{threeparttablex}
\usepackage{longtable}
\newlength{\mylength} \settowidth{\mylength}{$-55.55\pm0.55$}
\makeatletter
\newcommand\notsotiny{\@setfontsize\notsotiny{6.5}{7.5}}
\makeatother
\newcommand{\ts}[1]{\textsubscript{#1}}
\begin{document}
\begin{landscape}
\sisetup{
table-number-alignment=center,
separate-uncertainty=true,
table-column-width = 2cm,
table-format =-2.2,
separate-uncertainty,
table-figures-uncertainty=1, table-space-text-post=(16)}
\begin{ThreePartTable}
\notsotiny
\setlength{\tabcolsep}{2.3pt}
\setlength{\extrarowheight}{2.2pt}
\begin{longtable}{>{\itshape}p{2cm}p{0.8cm}@{}*{12}{S}@{}}%
\caption{Taxon}\\
\toprule
\multicolumn{2}{c}{Site} & \multicolumn{2}{c}{WI} & \multicolumn{2}{c}{WO} & \multicolumn{2}{c}{SL} & \multicolumn{2}{c}{SE} & \multicolumn{2}{c}{EO} & \multicolumn{2}{c}{EI} \\
\cmidrule(lr){3-4} \cmidrule(lr){5-6} \cmidrule(lr){7-8} \cmidrule(lr){9-10} \cmidrule(lr){11-12} \cmidrule(lr){13-14}
\multicolumn{2}{c}{Season}& {Wet} &{Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {\makebox[\mylength]{Dry}} \\
\midrule
\multicolumn{1}{c}{{Species}} & Tracer & {Mean $ \pm$ SD $_{(n)}$} & {Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} \\
\midrule
\endfirsthead
\multirow{2}{*}{\shortstack[l]{{Genus}\\ { Species}}}& $\delta{^{15}}$N & & & & & & 12.82\pm0.36\ts{(4)} & & & 13.83\pm0.99\ts{(8)} & 14.25\pm0.49\ts{(2)} & 14.60\pm0.23\ts{(4)} & \\
& $\delta{^{13}}$C & & & & & & -16.73\pm0.29\ts{(4)} & & & -16.62\pm0.27\ts{(8)} & -17.30\pm0.14\ts{(2)} & -16.65\pm0.31\ts{(4)} & \\
\bottomrule
\end{longtable}
\end{ThreePartTable}
\end{landscape}
\begin{landscape}
\sisetup{
table-number-alignment=center,
separate-uncertainty=true,
table-column-width = 2cm,
table-format =-2.2,
separate-uncertainty,
table-figures-uncertainty=1, table-space-text-post=(16)}
\centering
\begin{threeparttable}
\notsotiny
\setlength{\tabcolsep}{2.3pt}
\setlength{\extrarowheight}{2.2pt}
\caption{Taxon}
\begin{tabular}{>{\itshape}p{2cm}p{0.8cm}@{}*{12}{S}@{}}%
\toprule
\multicolumn{2}{c}{Site} & \multicolumn{2}{c}{WI} & \multicolumn{2}{c}{WO} & \multicolumn{2}{c}{SL} & \multicolumn{2}{c}{SE} & \multicolumn{2}{c}{EO} & \multicolumn{2}{c}{EI} \\
\cmidrule(lr){3-4} \cmidrule(lr){5-6} \cmidrule(lr){7-8} \cmidrule(lr){9-10} \cmidrule(lr){11-12} \cmidrule(lr){13-14}
\multicolumn{2}{c}{Season}& {Wet} &{Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {Dry} & {Wet} & {\makebox[\mylength]{Dry}} \\
\midrule
\multicolumn{1}{c}{{Species}} & Tracer & {Mean $ \pm$ SD $_{(n)}$} & {Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} &{Mean $ \pm$ SD $_{(n)}$} \\
\midrule
\multirow{2}{*}{\shortstack[l]{{Genus}\\ { Species}}}& $\delta{^{15}}$N & & & & & & 12.82\pm0.36\ts{(4)} & & & 13.83\pm0.99\ts{(8)} & 14.25\pm0.49\ts{(2)} & 14.60\pm0.23\ts{(4)} & \\
& $\delta{^{13}}$C & & & & & & -16.73\pm0.29\ts{(4)} & & & -16.62\pm0.27\ts{(8)} & -17.30\pm0.14\ts{(2)} & -16.65\pm0.31\ts{(4)} & \\
\bottomrule
\end{tabular}
\end{threeparttable}
\end{landscape}
\end{document}